Jahresübersicht für das Jahr 2025
07 Jan 2025
Physikalisches Kolloquium
Institut für Physik 16:15 Uhr s.t., HS KPH |
| Hanna Kokko, JoGU Mainz | |
Do you think you understand sex and death? Why predictions about biological processes require more than just intuition | |
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Theorie-Palaver
Institut für Physik 14:00 Uhr s.t., Lorentz room (Staudingerweg 7, 5th floor) |
| Bernd Sturmfels, Max Planck Institute for Mathematics in the Sciences Leipzig | |
We discuss determinantal varieties for symmetric matrices that have zero blocks along the main diagonal. In theoretical physics, these arise as Gram matrices for kinematic variables in quantum field theories. We also explore the ideals of relations among functions in the matrix entries that serve as building blocks for conformal correlators. | |
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08 Jan 2025
PRISMA+ Colloquium
Institut für Physik 13:00 Uhr s.t., Lorentz-Raum, 05-127, Staudingerweg 7 |
| Prof. Dr. Kathrin Valerius, KIT | |
The mass of neutrinos is a fundamental open question in physics, impacting both the
Standard Model of elementary particles and cosmology. Precision measurements of weak
decay kinematics offer a laboratory-based, model-independent method to probe the absolute
neutrino mass scale. The KArlsruhe TRItium Neutrino experiment (KATRIN) seeks to detect
the subtle imprint of the neutrino mass in the endpoint region of the tritium beta-decay
spectrum. Combining a high-intensity gaseous molecular tritium source with a high-resolution
electrostatic filter using magnetic adiabatic collimation, KATRIN has set the most stringent
direct neutrino-mass limit at m(ν) < 0.8 eV/c2 (90% C.L.) based on an initial data set. Ongoing
data collection and analysis aim for a sensitivity below 0.3 eV/c2. Additionally, KATRIN’s
precision beta-spectrum data facilitates searches for new physics beyond the neutrino mass,
including sterile neutrinos, Lorentz invariance violation, and non-standard weak interactions.
This talk presents the latest results and future prospects of the experiment. | |
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09 Jan 2025
Seminar über Quanten-, Atom- und Neutronenphysik (QUANTUM)
Institut für Physik 14:15 Uhr s.t., IPH Lorentzraum 05-127 |
| Dr. Antoine Browaeys, CNRS, Palaiseau, France | |
Over the last twenty years, physicists have learned to manipulate individual quantum objects: atoms, ions, molecules, quantum circuits, electronic spins... It is now possible to build "atom by atom" a synthetic quantum matter. By controlling the interactions between atoms, one can study the properties of these elementary many-body systems: quantum magnetism, transport of excitations, superconductivity... and thus understand more deeply the N-body problem. More recently, it was realized that these quantum machines may find applications in the industry, such as finding the solution of combinatorial optimization problems.
This seminar will present an example of a synthetic quantum system, based on laser-cooled ensembles of individual atoms trapped in microscopic optical tweezer arrays. By exciting the atoms into Rydberg states, we make them interact, even at distances of more than ten micrometers. In this way, we study the magnetic properties of an ensemble of more than a hundred interacting ½ spins, in a regime in which simulations by usual numerical methods are already very challenging. Some aspects of this research led to the creation of a startup, Pasqal. | |
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14 Jan 2025
Theorie-Palaver
Institut für Physik 14:00 Uhr s.t., Lorentz room (Staudingerweg 7, 5th floor) |
| Wen-Yuan Ai, Vienna, OAW | |
The terminal bubble wall velocity in a first-order phase transition (FOPT) is a critical parameter that influences not only the gravitational wave power spectrum but also a wide range of FOPT-related phenomena, including baryogenesis and dark matter production. However, precise computation of this velocity remains challenging. In this talk, I will discuss how to establish bounds on bubble wall velocities using two straightforward approximations: the local thermal equilibrium (LTE) approximation and the ballistic approximation. We perform numerical calculations both for a model-independent analysis and within an example model, the singlet-extended Standard Model. | |
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Physikalisches Kolloquium
Institut für Physik 16:15 Uhr s.t., HS KPH |
| Stefan Ulmer, Heinrich Heine-Universtät Düsseldorf | |
The striking imbalance of matter and antimatter in our universe inspires experiments to compare the fundamental properties of matter/antimatter conjugates with high precision. The BASE collaboration at the antiproton decelerator of CERN is performing such high-precision comparisons with protons and antiprotons. Using advanced cryogenic Penning traps, we have performed the most precise comparison of the proton-to-antiproton charge-to-mass ratio with a fractional uncertainty of 16 parts in a trillion [1], and have invented a novel spectroscopy technique, that allowed for the first direct high-precision measurement of the antiproton magnetic moment with a fractional accuracy of 1.5 parts in a billion [2]. Together with our last measurement of the proton magnetic moment [3] this improves the precision of previous magnetic moment based tests of the fundamental CPT invariance by more than a factor of 3000. A time series analysis of the sampled magnetic moment resonance furthermore enabled us to set first direct constraints on the interaction of antiprotons with axion-like particles (ALPs) [4], and most recently, we have used our ultra-sensitive single particle detection systems to derive constraints on the conversion of ALPs into photons [5]. In parallel we are working on the implementation of new measurement technology to sympathetically cool antiprotons [6] and to apply quantum logic inspired spectroscopy techniques [7]. In addition to that, we are currently developing the transportable antiproton-trap BASE-STEP, partly developed at Mainz, to relocate antiproton spectroscopy experiments from CERN’s accelerator environment to dedicated precision laboratory space at Heinrich Heine University Düsseldorf, very recently, the first loaded transport of this trap has been demonstrated successfully I will give a general introduction to the topic, will review the recent results produced by BASE, with particular focus on recent developments towards an at least 10-fold improved coherent measurement of the antiproton magnetic moment, and towards the first antiproton transport.
[1] M. J. Borchert et al., Nature 601, 35 (2022).
[2] C. Smorra et al., Nature 550, 371 (2017).
[3] G. Schneider et al., Science 358, 1081 (2017).
[4] C. Smorra et al., Nature 575, 310 (2019).
[5] J. A. Devlin et al., Phys. Rev. Lett. 126, 041321 (2021).
[6] M. A. Bohman et al. Nature 596, 514 (2021)
[7] J. M Conrejo et al., New J. Phys. 23 073045 | |
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15 Jan 2025
PRISMA+ Colloquium
Institut für Physik 13:00 Uhr s.t., Lorentz-Raum, 05-127, Staudingerweg 7 |
| Prof. Dr. Henrique Araujo, Imperial College London, UK | |
Nature continues to torment us with several well-posed and important questions which we have collectively failed to answer over several decades. What is the composition of the elusive “dark matter” that accounts for most of the mass of the cosmos? And why is the sub-dominant fraction of ordinary matter itself composed of particles rather than antiparticles? These fundamental questions may be answered by “listening in” to a large collection of very quiet atoms at the core of extremely sensitive radiation detectors installed deep underground. The XLZD Rare Event Observatory will address these important topics by searching for the scattering of dark matter particles in a large liquid xenon detector, and by searching for the neutrinoless double-beta decay of Xe-136 nuclei – another process with profound implications for fundamental physics. I will present some of the latest results from the ongoing LZ experiment taking data at the Sanford Lab, and then review the scientific motivation for, and potential reach of, the next-generation effort – XLZD. Finally, I will set out our vision to host the experiment in a newly developed Boulby Underground Laboratory in the UK. | |
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16 Jan 2025
Seminar über Quanten-, Atom- und Neutronenphysik (QUANTUM)
Institut für Physik 14:15 Uhr s.t., IPH Lorentzraum 05-127 |
| Dr. Vera Schäfer, MPI Heidelberg | |
Precision measurements of atomic transition frequencies have become a promising path for testing theories for new physics beyond the standard model. To achieve even higher precision more stable and narrow-linewidth laser sources are required.
Superradiant lasers are a candidate for realising a narrow-linewidth, high-bandwidth active frequency reference. They shift the phase memory from the optical cavity, which is subject to technical and thermal vibration noise, to an ultra-narrow optical atomic transition of an ensemble of cold atoms trapped inside the cavity. Our previous demonstration of pulsed superradiance on the mHz transition in 87Sr achieved a fractional Allan deviation of 6.7*10−16 at 1s of averaging. Moving towards continuous-wave superradiance promises to further improve the short-term frequency stability by orders of magnitude. A key challenge is the continuous supply of cold atoms into a cavity, while staying in the collective strong coupling regime.
We demonstrate continuous loading and transport of cold 88Sr atoms inside a ring cavity, after several stages of laser cooling and slowing. We further describe the emergence of distinct zones of collective continuous lasing of the atoms on the 7.5kHz transition, 7x narrower than the cavity linewidth, and pumped by the cooling lasers via inversion of the motional states. The lasing is supported by self-regulation of the number of atoms inside the cavity that pins the dressed cavity frequency to a fixed value over >3MHz of raw applied cavity frequency. In the process up to 80% of the original atoms are expelled from the cavity.
I will also present a new project in Heidelberg aiming to use precision spectroscopy of highly charged ions to search for a variation of the fine-structure constant. | |
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Seminar über Theorie der kondensierten Materie / TRR146 Seminar
F. Schmid / G. Settanni / P. Virnau / L. Stelzl 14:30 Uhr s.t., Minkowski-Raum, 05-119, Staudingerweg 7 |
| Hendrik Ranocha, Prof. Dr. | |
Compressible computational fluid dynamics (CFD) is an active and
fruitful area of research. In this talk, we will focus on time
integration methods optimized for CFD applications. We will briefly
review the classical Courant-Friedrichs-Lewy (CFL) constraint and
present error-based time step size control as an alternative. In
particular, we will discuss how the design of the methods influences
their efficiency and robustness. Combining theoretical analysis with a
data-driven approach, we will present new optimized time integration
methods for compressible CFD applications that are available in
open-source software. | |
| at Zoom | |
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21 Jan 2025
Physikalisches Kolloquium
Institut für Physik 16:15 Uhr s.t., HS KPH |
| Nancy Paul, Laboratoire Kastler Brossel, Jussieu | |
From dark matter and dark energy to neutrino oscillations and the lack of antimatter in the universe, there is growing evidence that the Standard Model is incomplete. Tests of Quantum Electrodynamics (QED) with few-electron systems offer a promising avenue for looking for new physics, as QED is the best understood quantum field theory and extremely precise predictions can be obtained for few-electron systems. Unfortunately, despite decades of effort, QED is poorly tested in the regime of strong coulomb fields, precisely the region where new exotic physics may be most visible. I will present a new paradigm for probing higher-order QED effects using spectroscopy of Rydberg states in exotic atoms, where orders of magnitude stronger field strengths can be achieved while nuclear uncertainties may be neglected. Such tests are now possible due to the advent of quantum sensing microcalorimeter x-ray detectors and new facilities providing low-energy intense beams of exotic particles for precision physics. First measurements have been successfully conducted at J-PARC with muonic atoms, but antiprotonic atoms offer the highest sensitivity to strong-field QED. I will present an overview of the PAX project, a new experiment for antiprotonic atom x-ray spectroscopy with a large-area transition edge sensor (TES) x-ray detector and low-energy cyclotron trap at ELENA. Finally, the experimental paradigm can also be reversed such to study low-lying states and access nuclear properties, such as those pursued in the QUARTET collaboration at Paul Scherrer Institute to improve the charge radii of light nuclei. I will present first results from QUARTET, and discuss synergies between atomic and nuclear physics accessible with these experiments. | |
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Theorie-Palaver
Institut für Physik 14:00 Uhr s.t., Lorentz room (Staudingerweg 7, 5th floor) |
| Jungwon Lim, Max Planck Institute for Physics, Munich | |
This talk will present the detailed procedure of computing three-loop four-point Feynman integrals with one massive leg and the applications to three-point form factors and Higgs plus jet amplitudes. In the first part, I will discuss technical details of computing three-loop four-point Feynman integrals using differential equation methods. In the second part, I will discuss about the analytic properties of the form factors and recent updates on the form factors and Higgs plus jet amplitude. | |
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22 Jan 2025
PRISMA+ Colloquium
Institut für Physik 13:00 Uhr s.t., Lorentz-Raum, 05-127, Staudingerweg 7 |
| Dr. Wilf Shorrock, University of Sussex, UK | |
The NOvA neutrino oscillation experiment has been collecting data for over 10 years. Since the last NOvA analysis, the neutrino dataset has almost doubled, and there have been several improvements to the treatment of systematics and physics models. The most recent results introduce a new low energy electron neutrino sample and give the most precise single-experiment measurement of ?m_32^2 to date. My talk will give an extensive overview of the NOvA experiment and their latest results, as well as looking at the future of NOvA and neutrino oscillation experiments. Slides here... | |
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23 Jan 2025
Seminar über Quanten-, Atom- und Neutronenphysik (QUANTUM)
Institut für Physik 14:15 Uhr s.t., IPH Lorentzraum 05-127 |
| Prof. Dr. Tobias Schätz, Universität Freiburg | |
The field of ultra-cold chemistry of ions and atoms has been launching the fundamental quest for investigating its quantum regime for decades. A simplifying summary of the quest might be:
How do interactions and chemical reactions proceed at extremely low temperatures? The classical picture predicts that all dynamics comes to a standstill as zero velocity is approached. However, deviations are expected since the classical model ceases to be appropriate at microscopic scales and at low temperatures, where particle-wave dualism of matter get’s important. In this regime, quantum effects dominate and reactions are predicted to obey fundamentally different rules.
Examples are:
(i) collisions of atoms, necessary for a reaction, cannot be described as a billiard-like impact between hard spheres anymore, but rather as interfering waves, interacting at long range, which can coherently amplify or even decoherently annihilate each other.
(ii) energy barriers can exceed the available kinetic energy, but nevertheless be efficiently passed via quantum tunnelling, ruling the dynamics.
Experimentally, we immerse a single barium (Ba+) ion in a bath of fermionic lithium (Li) atoms. We span temperatures from far above room temperature down deep into the s-wave regime of nano-Kelvin. We report our results on exploiting the collision energy dependence of magnetically tunable atom-ion scattering (Feshbach) resonances and explain how to assign their partial-wave-classification experimentally.
In the first half, we will give a basic tutorial on quantum scattering of atom-ion ensembles and distill the substantial differences to atom-atom dynamics. We aim to discuss how to gain control and state-sensitive detection on the level of individual quanta within the merged ion-atom system and to study and establish optically trapping of ions and atoms in general - for example to reveal the quantum dynamics of ion-atom and ion-molecule reactions in absence of any detrimental radio-frequency fields. | |
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28 Jan 2025
Physikalisches Kolloquium
Institut für Physik 16:15 Uhr s.t., HS KPH |
| Peter Düben, European Centre for Medium-Range Weather Forecasts (ECMWF) | |
This talk will outline three revolutions that happened in the past decades in the development of Earth system models that are used to perform weather and climate predictions. The quiet revolution has leveraged better observations and more compute power to allow for constant improvements of prediction quality of the last decades, the digital revolution has enabled us to perform km-scale simulations on modern supercomputers that further increase the quality of our models, and the machine learning revolution has now shown that machine learned weather models are often competitive with physics based weather models for many forecast scores while being easier, smaller and cheaper. This talk will summarize the past developments, explain current challenges and opportunities, and outline how the future of Earth system modelling will look like. In particular, regarding machine-learned foundation models in a physical domain such as Earth system science. | |
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Theorie-Palaver
Institut für Physik 14:00 Uhr s.t., Lorentz room (Staudingerweg 7, 5th floor) |
| Stéphane Lavignac, Institut de Physique Théorique, Université Paris Saclay | |
The observed matter-antimatter asymmetry of the Universe cannot be explained within the Standard Model and requires new physics. Interestingly, the simplest extension of the Standard Model that can generate Majorana masses for neutrinos contains all the ingredients needed to create an excess of matter over antimatter in the early Universe, via a mechanism called leptogenesis. In this talk, I will discuss the connections between neutrino masses, CP violation in the lepton sector and the matter-antimatter asymmetry of the Universe, and discuss different leptogenesis scenarios. In particular, I will present recent work about leptogenesis during a cosmological first order phase transition. | |
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29 Jan 2025
PRISMA+ Colloquium
Institut für Physik 13:00 Uhr s.t., Lorentz-Raum, 05-127, Staudingerweg 7 |
| Prof. Dr. Claudio Gatti, Frascati, Italy | |
Quantum Sensing for High Frequency Gravitational Waves and Axion Dark Matter: Microwave cavities in strong magnetic fields are among the most promising tools for detecting dark-matter axions and high-frequency gravitational waves. These searches rely on the Primakoff and Gertsenshtein effects, which predict the conversion of axions and gravitational waves, respectively, into electromagnetic radiation in the presence of a strong static magnetic field. In a microwave cavity, this interaction leads to the displacement of the vacuum state of the resonant mode, generating a coherent electromagnetic signal. Given the expected signal weakness, developing detectors with sensitivity beyond the quantum limit is crucial. In the C and X bands of the electromagnetic spectrum, superconducting qubits have demonstrated exceptional performance for this purpose. However, strong magnetic fields pose challenges, requiring either signal transport to a shielded region or the use of magnetically resilient devices. Additionally, qubit state readout errors due to noise and dephasing limit sensitivity. These challenges can be mitigated through quantum non-demolition measurements, either by repeating the measurement over time or employing multiple qubits simultaneously. During the seminar, we will discuss ongoing developments at the COLD laboratory of the INFN Frascati National Laboratories, focusing on non-demolitive measurement techniques and the development of magnetically resilient qubits.
1. R. Moretti et al., “Transmon qubit modeling and characterization for Dark Matter search,” arXiv:2409.05988.
2. A. Rettaroli et al. “Novel two-qubit microwave photon detector for fundamental physics applications,” Nuclear Instruments and Methods in Physics Research A 1070 (2025) 170010.
3. A. D’Elia et al. “Characterization of a Transmon Qubit in a 3D Cavity for Quantum Machine Learning and Photon Counting,” Appl. Sci. 2024, 14(4), 1478.
4. QUAX Collaboration “Search for axion dark matter with the QUAX–LNF tunable haloscope” Phys. Rev. D 110, 022008 (2024). Slides here... | |
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30 Jan 2025
Seminar über Quanten-, Atom- und Neutronenphysik (QUANTUM)
Institut für Physik 14:15 Uhr s.t., IPH Lorentzraum 05-127 |
| Prof. Dr. Dominik Bucher, Technische Universität München | |
In my talk, I will present a novel approach to magnetic resonance microscopy that exploits nitrogen-vacancy (NV) centers in diamond for optically detected magnetic resonance (ODMR). The fusion of optical microscopy and nuclear magnetic resonance (NMR) spectroscopy bypasses the conventional reliance on k-space sampling and magnetic field gradients for spatial encoding of NMR signals, enabling real-space magnetic resonance imaging (MRI).
We demonstrate the capabilities of our widefield optical NMR microscopy technique by imaging NMR signals within a model microstructure, achieving a spatial resolution of approximately 10 μm over an area of ~235 × 150 μm². Each camera pixel captures a complete NMR spectrum, providing comprehensive information on signal amplitude, phase, local magnetic field strengths, and gradients. The integration of optical microscopy and NMR opens up new possibilities for a wide range of applications in the physical and life sciences, which I will discuss in the last part of my talk. These applications include imaging metabolic activity in single cells or tissue slices, analyzing battery materials, and facilitating high-throughput NMR analysis. | |
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Seminar über Theorie der kondensierten Materie / TRR146 Seminar
F. Schmid / G. Settanni / P. Virnau / L. Stelzl 14:30 Uhr s.t., Minkowski-Raum, 05-119, Staudingerweg 7 |
| René van Roij, Prof. Dr. | |
Title: Circuits of Microfluidic Memristors: Computing with Aqueous Electrolytes
Speaker: René van Roij, Institute for Theoretical Physics, Utrecht University, The Netherlands
Abstract: In this online talk we will discuss recent advances in our understanding of the physics of
cone-shaped microfluidic channels under static and pulsatile voltage- and pressure drops. On the
basis of Poisson-Nernst-Planck-Stokes equations for transport of aqueous electrolytes through
channels carrying a surface charge, we will provide a theoretical explanation for the experimentally
observed diode-like current rectification of these channels. At steady electric driving this
rectification involves salt depletion or accumulation in the channel depending on the sign of the
applied voltage [1], and this effect also explains the observed pressure-sensitivity of the electric
conductance. An extension towards an applied AC voltage predicts these channels to be tunable
between diodes at low frequencies ωτ<<1, memristors (resistors with memory) at intermediate
frequencies ωτ ~ 1, and Ohmic resistors at high frequency ωτ>>1 , with a characteristic (memory
retention) time τ proportional to the square of the channel length [2]. We predict that Hodgkin-
Huxley-inspired iontronic circuits of short (fast) and long (slow) conical channels yield neuromorphic
responses akin to (trains of) action potentials [2] and several other neuronic spiking modes [3]. Next,
we show theoretically and experimentally that a tapered microfluidic channel filled with an aqueous
nearly close-packed dispersion of colloidal charged spheres is a much stronger memristor than the
channel with only surface charges on the channel wall [4]. Upon applying a train of four positive
(negative) voltage pulses, each pulse representing a binary “1” (“0”), we map the hexadecimal
number represented by this train on an analog channel conductance, which offers opportunities for
reservoir computing -we give a proof of principle for the case of recognizing hand-written digits [4].
Finally we will also discuss recent and ongoing work on iontronic information processing. We exploit
the mobility of the medium (water) by considering simultaneously applied pulsatile pressure and
voltage signals to increase the bandwidth [5]. Finally, the versatile ionic nature of the charge carriers
allows for Langmuir-like ionic exchange reaction kinetics on the channel surface [6]. We show that
this can give rise to direct iontronic analogues of synaptic long-term potentiation and coincidence
detection of electric and chemical signals [7], which are both ingredients for brain-like (Hebbian)
learning.
References:
[1] W.Q. Boon, T. Veenstra, M. Dijkstra, and R. van Roij, Pressure-sensitive ion conduction in a conical
channel: optimal pressure and geometry, Physics of Fluids 34, 101701 (2022).
[2] T.M. Kamsma, W.Q. Boon, T. ter Rele, C. Spitoni, and R. van Roij, Iontronic Neuromorphic
Signaling with Conical Microfluidic Memristors, Phys. Rev. Lett. 130, 268401 (2023).
[3] T.M Kamsma, E. A. Rossing, C. Spitoni, and R. van Roij, Advanced iontronic spiking modes with
multiscale diffusive dynamics in a fluidic circuit, Neuromorph. Comput. Eng. 4 024003 (2024).
[4] T.M. Kamsma, J. Kim, K. Kim, W.Q. Boon, C. Spitoni, J. Park, and R. van Roij, Brain-inspired
computing with fluidic iontronic nanochannels, PNAS 121, e23202242121 (2024).
[5] A. Barnaveli, T.M. Kamsma, W.Q. Boon, and R. van Roij, Pressure-gated microfluidic memristor for
pulsatile information processing, arXiv:2404.15006.
[6] W.Q. Boon. M. Dijkstra, and R. van Roij, Coulombic Surface-Ion Interactions Induce Nonlinear and
Chemistry-Specific Charging Kinetics, Phys. Rev. Lett. 130, 058001 (2023).
[7] T.M. Kamsma, M. Klop, W.Q. Boon, C. Spitoni, and R. van Roij, arXiv:2406.03195 | |
| at Zoom | |
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04 Feb 2025
Physikalisches Kolloquium
Institut für Physik 16:15 Uhr s.t., HS KPH |
| Almudena Arcones, TU Darmstadt | |
Our understanding of the origin of heavy elements by the r-process (rapid neutron capture process) has made
great progress in the last years. In addition to the gravitational wave and kilonova observations for GW170817,
there have been major advances in the hydrodynamical simulations of neutron star mergers and core-collapse
supernovae, in the microphysics included in those simulations (neutrinos and high density equation of state), in
galactic chemical evolution models, in observations of old stars in our galaxy and in dwarf galaxies. This talk
will report on recent breakthroughs in understanding the extreme environments in which the formation of the
heavy elements occurs, as well as open questions regarding the astrophysics and nuclear physics involved. | |
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Seminar über Quanten-, Atom- und Neutronenphysik (QUANTUM)
Institut für Physik 12:00 Uhr s.t., IPH, Curie-Raum (03-431) |
| Dr. Michael Buchhold, Universität zu Köln | |
Understanding and actively shaping quantum entanglement in many-body systems is a key challenge for modern quantum technologies. Recently, monitored quantum dynamics — quantum dynamics with mid-circuit measurements — has emerged as a powerful tool for harnessing entanglement in NISQ devices and simulating non-equilibrium dynamics in condensed matter systems. In this talk, I will discuss our recent understanding of entanglement in monitored quantum dynamics from the viewpoint of emergent many-body phases and universality. Monitored dynamics generate wave functions with robust entanglement structures, which depend only on global properties such as symmetry and dimensionality, thereby defining entanglement phases of monitored quantum matter. We anticipate a symmetry classification of monitored matter akin to equilibrium quantum matter in Hamiltonian systems, which I will introduce using exemplary systems in one and two dimensions. I will also highlight our recent analytical and numerical advances and how they can be applied to engineer entanglement, for instance, in adaptive quantum circuits and driven quantum materials. | |
Vortrag im Rahmen der QuCoLiMa talks |
05 Feb 2025
PRISMA+ Colloquium
Institut für Physik 13:00 Uhr s.t., Lorentz-Raum, 05-127, Staudingerweg 7 |
| Prof. Dr. Yael Shadmi, Technion, Israel | |
The LHC experiments are now probing the Higgs interaction for the first time. Over the next two decades, they will supply a wealth of precise measurements of processes involving the Higgs and electroweak gauge bosons, which may provide clues to the origin of the Higgs potential and in particular, to the origin of the weak scale. How do we interpret these measurements? We will describe a model-independent approach, based on just the physical degrees of freedom, namely, the known particles, in terms of amplitudes. Slides here... | |
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13 Feb 2025
Seminar über Theorie der kondensierten Materie / TRR146 Seminar
F. Schmid / G. Settanni / P. Virnau / L. Stelzl 14:30 Uhr s.t., Minkowski-Raum, 05-119, Staudingerweg 7 |
| Frauke Gräter, Prof. Dr. | |
Enhancing scale-bridging simulations by machine learning – or substituting them altogether? | |
| at Zoom | |
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07 Apr 2025
Seminar über die Physik der kondensierten Materie (SFB/TRR173 Spin+X und SFB/TR288 Kolloquium, TopDyn-Seminar)
JGU 14:00 Uhr s.t., 05-427 Sozialraum der Thep |
| Prof. Junichiro Kono, Rice University Houston United States | |
Recent advances in optical studies of condensed matter have led to the emergence of a variety of phenomena that have conventionally been studied in quantum optics. These studies have not only deepened our understanding of light-matter interactions but also introduced aspects of many-body effects inherent in condensed matter. This talk will describe our recent studies of Dicke cooperativity, i.e., many-body enhancement of light-matter interaction, a concept in quantum optics, in condensed matter. This enhancement has led to the realization of the ultrastrong coupling (USC) regime, where new phenomena emerge through the breakdown of the rotating wave approximation (RWA). We will first describe our observation of USC in a 2D electron gas in a high-Q terahertz cavity in a magnetic field, and definitive evidence for the vacuum Bloch-Siegert shift, a signature of the breakdown of the RWA. Further, we have shown that cooperative USC also occurs in magnetic solids in the form of matter-matter interaction, i.e., spin-magnon and magnon-magnon interactions in rare earth orthoferrites. Particularly, the exchange interaction of N paramagnetic Er3+ spins with an Fe3+ magnon field in ErFeO3 has exhibited a vacuum Rabi splitting whose magnitude is proportional to N1/2 [6]. In the lowest temperature range, these cooperative interactions lead to a magnonic superradiant phase transition. These results provide a route for understanding, controlling, and predict novel phases of condensed matter. | |
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Seminar über die Physik der kondensierten Materie (SFB/TRR173 Spin+X und SFB/TR288 Kolloquium, TopDyn-Seminar)
JGU Sonderseminar: 14:00 Uhr s.t., 05-427 Sozialraum der Thep |
| Prof. Junichiro Kono, Rice University Houston United States | |
Recent advances in optical studies of condensed matter have led to the emergence of a variety of phenomena that have conventionally been studied in quantum optics. These studies have not only deepened our understanding of light-matter interactions but also introduced aspects of many-body effects inherent in condensed matter. This talk will describe our recent studies of Dicke cooperativity, i.e., many-body enhancement of light-matter interaction, a concept in quantum optics, in condensed matter. This enhancement has led to the realization of the ultrastrong coupling (USC) regime, where new phenomena emerge through the breakdown of the rotating wave approximation (RWA). We will first describe our observation of USC in a 2D electron gas in a high-Q terahertz cavity in a magnetic field, and definitive evidence for the vacuum Bloch-Siegert shift, a signature of the breakdown of the RWA. Further, we have shown that cooperative USC also occurs in magnetic solids in the form of matter-matter interaction, i.e., spin-magnon and magnon-magnon interactions in rare earth orthoferrites. Particularly, the exchange interaction of N paramagnetic Er3+ spins with an Fe3+ magnon field in ErFeO3 has exhibited a vacuum Rabi splitting whose magnitude is proportional to N1/2 [6]. In the lowest temperature range, these cooperative interactions lead to a magnonic superradiant phase transition. These results provide a route for understanding, controlling, and predict novel phases of condensed matter. | |
Sonderseminar | |
Special Event |
15 Apr 2025
Physikalisches Kolloquium
Institut für Physik 16:15 Uhr s.t., HS KPH |
| Andrew Webb, Leiden University Medical Centre, NL | |
Magnetic resonance imaging is an inherently non-invasive technique with biological applications from the cellular to human size-scales. A major technological push has been towards stronger magnetic fields, which can be >20 Tesla for preclinical studies and >10 Tesla for humans, since these increase the signal strength and ultimate imaging resolution. Such systems, however, require advances in hardware design, acquisition sequences and image processing algorithms to achieve optimal performance. The first part of this talk will concentrate on technical challenges and practical approaches for human scanning at 7 Tesla and above. The challenges include B_1 and B_0 inhomogeneities, increased specific absorption rate, and high sensitivity to movement. Neurological and neuroscience applications discussed include ocular and neurological tumours, epilepsy, neuromuscular diseases, glymphatic clearance and mechanistic studies of lithium for bipolar disorders. The second part will discuss the opposite end of the MRI spectrum, ultra-low field systems at ~50 mT which have been designed to address the challenges of global healthcare accessibility. The challenges here are diametrically opposite to those at high field, and topics of system design, characterization and in vivo applications will be highlighted. | |
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Theorie-Palaver
Institut für Physik 14:00 Uhr s.t., Lorentz room (Staudingerweg 7, 5th floor) |
| Eleftheria Solomonidi, Siegen U. | |
The CP violation observed in the hadronic decays of charmed mesons remains a puzzling open question for theorists. Calculations relying on the assumption of inelastic final-state interactions occurring between the pairs of pions and kaons fall short of the experimental value. It has been pointed out that a third channel of four pions can leave imprints on the CP asymmetries of the two-body decays. At the same time, plenty of data are available for rare decays such as \(D^0\to\pi^+\pi^-\ell^+\ell^-\), which provide a promising environment for the search for new physics. With this motivation, we study the cascade topology \(D^0\to a_1(1260)^+(\to \rho(770)^0\pi^+)\,\pi^-\), which has been measured to contribute significantly to the \(4\pi\) decays of the same meson, and estimate its effect on the branching ratio of the rare decays. I will also comment on the possibility of this topology contributing to the decay amplitude of \(D^0\to\pi^+\pi^-\) and by extension to the related CP asymmetry. | |
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16 Apr 2025
PRISMA+ Colloquium
Institut für Physik 13:00 Uhr s.t., Lorentz-Raum, 05-127, Staudingerweg 7 |
| Prof. Dr. Antoine Kouchner, APC, France | |
Thanks to their extremely weak interaction with matter and neutral electric charge, neutrinos travel vast cosmic distances without deflection, providing a unique and complementary approach to investigating the most energetic events in the Universe.
Neutrino telescopes are designed to detect Cherenkov light inferred by neutrino interactions. After more than fifteen years of data collection, the pioneering ANTARES detector has been successfully dismantled, making way for its next-generation successor, KM3NeT, deployed at two sites in the Mediterranean Sea. Near the former ANTARES location, off the coast of Toulon (France), KM3NeT/ORCA is dedicated to studying the intrinsic properties of atmospheric neutrinos through their oscillations within the Earth. Further southeast, off the coast of Sicily, KM3NeT/ARCA is monitoring the high-energy sky in search of cosmic neutrinos.
In this presentation, I will highlight the latest insights in neutrino (astro)physics emerging from the depths of the Mediterranean. Particular attention will be given to the recent detection of an ultra-high-energy neutrino event, designated KM3-230213A, by KM3NeT/ARCA. The observed particle is a muon with an estimated energy of 120+110−60 PeV. Its exceptionally high energy and nearly horizontal trajectory suggest that its parent neutrino originated from a cosmic accelerator or could potentially be the first detected cosmogenic neutrino—produced when ultra-high-energy cosmic rays interact with background photons in the Universe. This groundbreaking observation underscores the remarkable capabilities of deep-sea neutrino telescopes in unveiling new astrophysical phenomena.
To also view graphic content, follow the link:
https://www.thep.physik.uni-mainz.de/files/2025/04/Title_Abstract_Mainz_AK_16.04.2025.pdf Slides here... | |
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17 Apr 2025
Seminar über Quanten-, Atom- und Neutronenphysik (QUANTUM)
Institut für Physik 14:15 Uhr s.t., IPH Lorentzraum 05-127 |
| Dr. Hendrik Bekker, Helmholtz Institut Mainz | |
We aim to advance antimatter research through tabletop experiments that operate independently of accelerator infrastructure, allowing for much lower noise levels and freedom from beamtime schedules. Our approach involves Dual RadioFrequency Traps (DRFTs) to confine the constituents of antihydrogen: positrons and antiprotons. Due to the different charge-to-mass ratios, each species primarily couples to a separate RF field. Unlike other traps, DRFTs naturally allow two species, even those of opposite charge, to be brought close together so that high production rates of antihydrogen can be achieved. Additionally, their open geometry is advantageous for laser spectroscopy. In our pioneering study, we develop a DRFT for co-trapping electrons and calcium ions which act as stand-ins for positrons and antiprotons. We demonstrate seperate storage times of up to a second and are developing an improved DRFT to extend this. In parallel, we are developing a low-energy positron source which will allow us to study bound positron-atom systems while other groups work on developing tools to transport antiprotons for future studies on antihydrogen. | |
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22 Apr 2025
Theorie-Palaver
Institut für Physik 14:00 Uhr s.t., Lorentz room (Staudingerweg 7, 5th floor) |
| Duarte Fontes, KIT | |
Muon conversion — the process of a bound muon decaying into an energetic electron — is one of the best probes of charged lepton flavor violation. The experimental limit is soon expected to improve by four orders of magnitude, thus calling for precise predictions on the theory side. Equally important are precise predictions for muon decay-in-orbit, the main background for muon conversion. While the calculation of electromagnetic corrections to the two processes above the nuclear scale does not involve significant challenges, it becomes substantially more complex below that scale due to multiple scales, bound-state effects and experimental setup. In this talk, I present a systematic framework that addresses these challenges by resorting to a series of effective field theories. Combining Heavy Quark Effective Theory (HQET), Non-Relativistic QED (NRQED), potential NRQED, Soft-Collinear Effective Theory I and II, and boosted HQET, I derive a factorization theorem and present the renormalization group equations. | |
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23 Apr 2025
PRISMA+ Colloquium
Institut für Physik 13:00 Uhr s.t., Lorentz-Raum, 05-127, Staudingerweg 7 |
| Prof. Dr. Xianguo Lu, University of Warwick, England, UK | |
Neutrinos, though nearly massless and weakly interacting, play a central role in modern physics—from the origin of mass and the nature of matter–antimatter asymmetry to the search for physics beyond the Standard Model. Yet one of the main obstacles to fully realising their potential lies in our limited understanding of how neutrinos interact with matter. These interactions are complex, often involving nuclear effects that are difficult to model and challenging to measure. As a result, they introduce significant systematic uncertainties in precision experiments, including those aiming to determine mixing parameters and explore CP violation.
This talk will provide an accessible overview of why neutrino interaction physics is both essential and challenging, and how it connects nuclear and particle physics. I will outline current experimental limitations and discuss the key requirements for future progress: well-characterised neutrino beams, dedicated measurements, and new experimental strategies. These advances are not only crucial for interpreting results from current and future experiments, but also for enabling discoveries that may reshape our understanding of fundamental physics. As an illustrative example, I will introduce nuSTORM—a proposed facility based on stored muons—as a next-generation platform for precision neutrino scattering and searches for new physics. Slides here... | |
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24 Apr 2025
Seminar über Quanten-, Atom- und Neutronenphysik (QUANTUM)
Institut für Physik 14:15 Uhr s.t., IPH Lorentzraum 05-127 |
| Prof. Dr. Piet O. Schmidt, Physikalisch-Technische Bundesanstalt & Leibniz Universität Hannover | |
Optical atomic clocks with eighteen significant digits are the most accurate measurement devices available to us with applications ranging from tests of fundamental physics to height difference measurements in relativistic geodesy. The uncertainty in trapped-ion clocks is limited by systematic frequency shifts and quantum projection noise. In my presentation, I will show how quantum engineering techniques can overcome these limitations. Quantum algorithms provide access to new clock species such as highly charged ions with reduced systematic shifts and high sensitivity to searches for new physics, including hypothetical fifth forces, variation of fundamental constants and dark matter candidates. Dynamical decoupling and entangled state spectroscopy in a multi-ion frequency reference offer suppression of systematic shifts, while improving the signal-to-noise ratio of the clock and thus the required averaging time to reach a certain resolution. These developments will pave the way towards a next generation of quantum-enhanced clocks that enter the 10-19 relative frequency uncertainty regime. | |
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GRK 2516 Soft Matter Seminar
Uni Mainz 14:30 Uhr s.t., Minkowski Room, 05-119, Staudingerweg 7 |
| Shikha Dhiman, JGU, Chemistry | |
TBA | |
| at Zoom | |
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GRK 2516 Soft Matter Seminar
Uni Mainz 15:00 Uhr s.t., Minkowski Room, 05-119, Staudingerweg 7 |
| Michael te Vrugt, JGU, Physics | |
TBA | |
| at Zoom | |
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29 Apr 2025
Physikalisches Kolloquium
Institut für Physik 16:15 Uhr s.t., HS KPH |
| Frauke Gräter, Max Planck Institute for Polymer Research | |
Life is physics and chemistry in action. While molecular simulations of systems as complex as whole cells are now within reach, predicting chemical reactivity on relevant time and length scales remains a challenge. I will present our recent work towards bringing action – here: chemistry – to classical simulations and molecular design through machine learning.
Among others, we substitute costly quantum mechanical calculations with a graph neural network-based emulator. Our framework can deal with the plethora of life’s chemistry amidst the ‘jiggling and wiggling’ of biomolecules. Importantly, we also uncover unexpected biomolecular processes that we in turn put to test in experiments. Finally, I will demonstrate how we harness a flow-matching model to predict biomolecular dynamics. Our method paves the way for generating novel flexible and functional proteins. | |
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Theorie-Palaver
Institut für Physik 14:00 Uhr s.t., Lorentz room (Staudingerweg 7, 5th floor) |
| Simone Zoia, U. Zurich | |
Top-quark pair production in association with a jet is a key process at the LHC. Its high sensitivity to the top mass and the increasing experimental precision call for the QCD corrections to be computed at the next-to-next-to-leading order (NNLO). In this seminar, I will present the computation of the two-loop Feynman integrals required to obtain NNLO QCD predictions in the leading colour approximation. These integrals are characterised by significant algebraic complexity—stemming from the multi-scale, five-particle kinematics—as well as analytic complexity, due to the appearance of nested square roots and elliptic functions. I will discuss modern methods for tackling multi-scale integrals in a way that is suitable for phenomenology, and outline first steps to extend these techniques to cases involving elliptic functions. | |
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30 Apr 2025
PRISMA+ Colloquium
Institut für Physik 13:00 Uhr s.t., Lorentz-Raum, 05-127, Staudingerweg 7 |
| Prof. Dr. Daniel Stolarski, Carleton University, Ottawa, Canada | |
Quantum field theory (QFT), a framework that combines special relativity and quantum mechanics, is the language used to describe the fundamental particles and interactions of our universe. One of the most powerful tools in QFT is perturbation theory, which has given rise to some of the most precise predictions in science. There are QFTs, however, where perturbation theory does not work, the most prominent being the theory of the strong force, Quantum Chromodynamics. In this talk, I will describe some recently developed tools used to better understand non-perturbative QFTs. One of these tools is called supersymmetry, which allows one to treat the spherical cow of QFTs. Finally, I will explore whether these tools could be applicable to the real world strong force. Slides here... | |
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06 May 2025
Physikalisches Kolloquium
Institut für Physik 16:15 Uhr s.t., HS KPH |
| Yafang Cheng, Max Planck Institute for Chemistry | |
Aerosol chemistry: from molecular dynamics to atmospheric vortices | |
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Theorie-Palaver
Institut für Physik 14:00 Uhr s.t., Lorentz room (Staudingerweg 7, 5th floor) |
| Apostolos Pilaftsis, Manchester U. | |
By employing the Bloch-sphere formalism, I will present a novel class of unstable qubits, which are called Critical Unstable Qubits (CUQs). The characteristic property of CUQs is that the energy-level and decay-width Pauli vectors, E and Γ, are orthogonal to one another, and the key parameter r = |Γ|/(2|E|) is less than 1. A remarkable feature of CUQs is that they exhibit atypical behaviours like coherence-decoherence oscillations when analysed in an appropriately defined co-decaying frame of the system. In the same frame, I will show how a unit Bloch vector b describing a pure CUQ sweeps out unequal areas during equal intervals of time, while rotating about the vector E. These phenomena emerge beyond the usual oscillatory pattern due to the energy-level difference of a standard two-level quantum system. I will illustrate how these new features are relatively robust and persist even for quasi-CUQs, in which the vectors E and Γ are not perfectly orthogonal to each other. I discuss potential applications of our results to quantum information and to unstable meson-antimeson and other systems. | |
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07 May 2025
PRISMA+ Colloquium
Institut für Physik 13:00 Uhr s.t., Lorentz-Raum, 05-127, Staudingerweg 7 |
| Bhupal Dev, Washington University, St. Louis/USA | |
Neutrinos are the least known particles in the Standard Model. In particular, whether they are Dirac or Majorana particles is an important open question. Theoretically, it is also possible that they are pseudo-Dirac, which are fundamentally Majorana fermions, but essentially act like Dirac fermions in most experimental settings, due to extremely small active-sterile mass splitting. We will discuss how such tiny values of mass splitting can be accessed via oscillations over astrophysical baselines. We use the recent multi-messenger observations of high-energy neutrino sources to probe hitherto unexplored values of mass splitting, which improve the reach of terrestrial experiments by more than a billion. Finally, we will present an intriguing hint for nonzero active-sterile mass splitting in the recent IceCube data. Slides here... | |
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08 May 2025
Seminar über Quanten-, Atom- und Neutronenphysik (QUANTUM)
Institut für Physik 14:15 Uhr s.t., IPH Lorentzraum 05-127 |
| Dr. Denis Kopylov, Universität Paderborn Comp. Optoelectronics and Photonics | |
Currently, pulsed parametric down-conversion (PDC) in waveguides is one of the most promising platforms for non-classical light sources. PDC provides not only an efficient way to generate biphoton pairs and squeezed states but also can be used in more advanced circuits to prepare non-Gaussian states of light. However, waveguides typically possess surface imperfections that may cause significant scattering of the guided light, providing multimode mixed output states. In this talk, we discuss the properties of the multimode PDC in lossy waveguides and show how critical these losses are for the generation of biphoton, squeezed, and entangled states ([Quantum 9, 1621 (2025)] and [arXiv:2501.08917]). | |
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Theorie-Palaver
Institut für Physik Sonderseminar: 17:00 Uhr s.t., THEP Social Room |
| Motoko Fujiwara, U. of Toyama | |
Electroweakly interacting stable particles in the (1 − 10) TeV mass range can be a dark matter candidate with rich testability. In particular, gamma-ray line-like features are expected to be a smoking-gun signature for indirect detection. In this framework, one fundamental question follows: How can we distinguish DM spin among DM candidates with the same electroweak interaction by contrasting their predictions? A straightforward but crucial effort is to derive annihilation spectra with higher accuracy. However, one encounters complexities due to non-perturbative corrections following the mass hierarchy between heavy DM and electroweak mediators.
In this talk, we present how to construct Soft-Collinear Effective field Theory (SCET) to systematically resum large Sudakov logarithmic corrections for spin-0, 1/2, and 1 DM, and achieve accurate prediction. We focus especially on spin-1 DM, which is the last piece to complete all the possible predictions.
After specifying the leading operators to describe heavy DM annihilation in SCET, we discuss how to extract spin-dependence from the predicted gamma-ray spectrum. | |
Sonderseminar | |
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13 May 2025
Physikalisches Kolloquium
Institut für Physik 16:15 Uhr s.t., HS KPH |
| Anna Balazs, University of Pittsburgh, USA | |
Harnessing Chemo-Mechanical Interactions To Regulate Behavior Of Flexible Materials In Confined Fluids | |
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Theorie-Palaver
Institut für Physik 14:00 Uhr s.t., Lorentz room (Staudingerweg 7, 5th floor) |
| Rourou Ma, MPP, USTC | |
I will introduce our IBP package NeatIBP, which automatically generates small-size integration-by-parts (IBP) identities for Feynman integrals. Based on the syzygy and module intersection techniques, the generated IBP identities’ propagator degree is controlled and thus the size of the system of IBP identities is shorter than that generated by the standard Laporta algorithm. Resently, we updated NeatIBP with some new featrues, such as, spanning cut and the reduction interface of NeatIBP and Kira. I will also give some powerful applications of NeatIBP. | |
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14 May 2025
PRISMA+ Colloquium
Institut für Physik 13:00 Uhr s.t., Lorentz-Raum, 05-127, Staudingerweg 7 |
| Prof. Dr. Garrett King, Los Alamos, USA | |
Precision measurements involving nuclei are at the cutting edges of nuclear physics and testing the Standard Model (SM) of physics. For instance, precision beta decay measurements have the potential to constrain beyond SM physics at TeV scales. To interpret these experiments, it is crucial to have comparably accurate theoretical predictions of relevant quantities along with an accurate understanding of the underlying nuclear dynamics. In this contribution, I will overview recent calculations of electroweak processes with quantum Monte Carlo (QMC) computational methods used to solve the many-body Schr ̈odinger equation. The QMC approach retains the complexity of many-nucleon dynamics and provides highly accurate results for light nuclei. I will discuss calculations of observable quantities with readily available data–such as beta decay and electromagnetic reactions–used to validate models of nuclear many-body interactions and electroweak currents. I will present QMC calculations of predicted quantities relevant to on-going beta decay experiments and discuss how these results will impact experimental determinations of beyond standard model physics. Slides here... | |
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15 May 2025
Seminar über Quanten-, Atom- und Neutronenphysik (QUANTUM)
Institut für Physik 14:15 Uhr s.t., IPH Lorentzraum 05-127 |
| Dr. Danila Barskiy, Helmholtz Institute Mainz | |
We introduce quantum magnetic J-oscillators that operate at zero magnetic field by exploiting nuclear spin-spin J-coupling transitions in molecules. This is achieved by coupling in situ hyperpolarized samples to a programmable digital feedback system that digitizes, delays, and amplifies the sample-generated magnetic field before feeding it back to the sample. Due to the insensitivity of the J-couplings to magnetic field drifts, we achieved coherent J-oscillations lasting over 3000 s, with a linewidth of 337 μHz limited primarily by acquisition time, reaching the Cramér-Rao lower bound in estimating error in frequency measurement [1]. The ability to control the feedback delay and gain enabled us to resolve overlapping resonances, making possible on-demand spectral editing. Application of quantum oscillators was demonstrated on a diverse range of molecules (nitriles, heterocycles, organic acids). The J-oscillators produce highly resolved, sharp spectra, reveal hidden transitions, and may allow distinction of complex mixtures that conventional zero-field NMR [2] cannot resolve. As a result, this approach can expand the scope of zero-field NMR for analytical chemistry, biomolecular characterization, and fundamental physics.
[1]. S. Fleischer, S. Lehmkuhl, L. Lohmann, S. Appelt, Approaching the Ultimate Limit in Measurement Precision with RASER NMR. Appl. Magn. Reson. 54 (11), 1241–1270 (2023).
[2]. D. A. Barskiy, et al., Zero- to Ultralow-field Nuclear Magnetic Resonance. Prog. Nucl. Magn. Reson. Spectrosc. (2025). | |
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20 May 2025
Physikalisches Kolloquium
Institut für Physik 16:15 Uhr s.t., HS KPH |
| Libor Smejkal, JGU Mainz, INSPIRE Group | |
Symmetries play a key role in many areas of modern physics. For example, the symmetry-breaking paradigm describes how various phases of matter emerge. In magnetism, spontaneous symmetry breaking leads to well-known phases of ferromagnets and antiferromagnets. Ferromagnets have a net magnetization, while antiferromagnets have atomic magnetic moments that cancel out.
Surprisingly, recent research shows this magnetic dichotomy, developed in the 1930s, is incomplete [1-5]. In this talk, we introduce our recently developed classification of magnetic phases based on spin-lattice symmetries. These are pairs of operations in spin and lattice space. This unorthodox perspective has led us to identify two unconventional magnetic phases: altermagnets [4] (see figure) and antialtermagnets [5]. Like antiferromagnets, both have compensated magnetic order and thus no net magnetization. But unlike antiferromagnets—and similar to ferromagnets—they induce spin polarization in the electronic structure. The key distinction between altermagnets and antialtermagnets lies in their behaviour under time-reversal symmetry. Altermagnets break time-reversal symmetry in their electronic structure, resulting in features like d-wave spin order [2]. In contrast, antialtermagnets preserve time-reversal symmetry and exhibit properties such as p-wave spin order [5,6].
We’ll also explore how the concept of altermagnetism was inspired by our earlier theoretical prediction[1-2] and experimental observation of an unconventional spontaneous Hall effect[7]. Additionally, we’ll highlight recent photoemission experiments that have confirmed altermagnetic order in materials like MnTe and CrSb [8]. Finally, we’ll discuss the broader implications of altermagnetism and spin symmetries. These findings have potential applications in areas such as spintronics, magnonics, topological materials, 2D materials, and multiferroics [9]—all of which could lead to faster, smaller, and more energy-efficient AI-era information technologies [1,9]. | |
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Theorie-Palaver
Institut für Physik 14:00 Uhr s.t., Lorentz room (Staudingerweg 7, 5th floor) |
| Renato Maria Prisco, Napels U. | |
Precise numerical evaluation of Feynman integrals plays a central role in particle physics. While some methods focus on individual phase-space points, others exploit differential equations to efficiently propagate results across kinematic regions. LINE is a novel open-source program that integrates both strategies within a single tool, computing boundary values and propagating them accordingly. Written primarily in C, it is designed for performance and scalability, enabling large-scale computations on clusters without relying on proprietary software. In this talk, I will introduce the core ideas behind LINE and present a few representative applications. | |
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21 May 2025
PRISMA+ Colloquium
Institut für Physik 13:00 Uhr s.t., Lorentz-Raum, 05-127, Staudingerweg 7 |
| Prof. Dr. Andreas Jüttner, CERN, Geneva, Switzerland | |
The elements of the CKM matrix are fundamental parameters of the Standard Model. Substantial experimental and theory efforts are under way, aimed at determining them ever more precisely and accurately. Interestingly, some tensions between different approaches have persisted over many years, in particular, between determinations from inclusive and exclusive semi-leptonic meson decays, respectively. This talk addresses new ideas aimed at resolving these tensions. In particular, I will discuss how fundamental principles like analyticity and unitarity can be used to improve existing, and enable new computations in lattice QCD. The ideas will be demonstrated for the analysis of simulations of exclusive as well as inclusive semileptonic Bs-meson decay. In the former case, the use of Bayesian inference allows for formulating a model- and truncation independent parameterisation of hadronic form factors. In the latter case, the properties of the QCD transfer matrix are used to tackle the computation of the inclusive decay rate for the first time. Slides here... | |
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22 May 2025
GRK 2516 Soft Matter Seminar
Uni Mainz 14:30 Uhr s.t., Minkowski Room, 05-119, Staudingerweg 7 |
| Hans-Jürgen Butt, MPI-P | |
TBA | |
| at Zoom | |
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GRK 2516 Soft Matter Seminar
Uni Mainz 15:00 Uhr s.t., Minkowski Room, 05-119, Staudingerweg 7 |
| Regine von Klitzing, TU-Darmstadt, Physics | |
TBA | |
| at Zoom | |
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Seminar über die Physik der kondensierten Materie (SFB/TRR173 Spin+X und SFB/TR288 Kolloquium, TopDyn-Seminar)
JGU 14:00 Uhr s.t., 01 122 Newton-Raum |
| Rembert Duine, Eindhoven University of Technology | |
Synthetic antiferromagnets are magnetic multilayers consisting of two or more ferromagnetic layers that are coupled antiferromagnetically. They play an important role in spintronic devices, e.g., as field sensors, and as synthetic materials for fundamental explorations. In this talk, I will highlight the use of synthetic antiferromagnets for quantum information science with spin waves, i.e., for quantum magnonics. Examples that are discussed are unidirectionally-coupled magnetic layers that give rise to magnon quantum amplification, and new ways to entangle magnons between two ferromagnetic layers. Both these examples rely on the possibility to engineer both the interactions between the layers, and the interactions of the magnetic layers with the environment. This tunability highlights the potential of synthetic antiferromagnets for quantum magnonics. | |
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Seminar über Quanten-, Atom- und Neutronenphysik (QUANTUM)
Institut für Physik 14:15 Uhr s.t., IPH Lorentzraum 05-127 |
| Jun.-Prof. Dr. Michael Zopf, Leibniz Universität Hannover, Institut für Festkörperphysik | |
This talk explores the rapidly evolving field of quantum technologies, with a particular focus on semiconductor quantum dots (QDs) and their potential in quantum communication and distributed quantum computing. Quantum dots are excellent sources of single and entangled photons and offer significant tunability in their optical properties through variations in material composition, shape, and confinement. Our work focuses on epitaxially grown GaAs/AlGaAs QDs that emit near the optical transitions of rubidium or the zero-phonon line of silicon-vacancy centres [1]. There is strong potential for such QDs in hybrid systems, which are vital for future quantum repeaters and extended quantum networks [2]. Several milestone experiments have been realized, incorporating single quantum dots. These include entanglement swapping between photon pairs [3] and quantum key distribution (QKD) experiments between Hannover and Braunschweig [4]. In order for QDs to realise their full potential in quantum technology applications, it is imperative to realize a seamless integration of QDs into photonic devices, with the objective of enhancing the efficiency of photon extraction and optimising the coupling to fibre networks. This necessitates the development of innovative strategies in the fields of optical positioning, photonic design and fabrication. A calibration model is introduced with the objective of enhancing the accuracy of wide-field optical positioning for the alignment of solid-state single photon emitters within photonic nanostructures. This is expected to result in a significant increase in the yield of high performance quantum photonic devices. Furthermore, the development of hybrid circular photonic crystal gratings for the generation of entangled photon pairs at telecom wavelengths represents a promising advancement for direct coupling efficiency into single-mode fibres [5].
[1] X. Cao, J. Yang, T. Fandrich, Y. Zhang, E. P. Rugeramigabo, B. Brechtken, R. J. Haug, M. Zopf, and F. Ding, Nano Letters 23, 6109 (2023).
[2] P. van Loock, W. Alt, C. Becher, O. Benson, H. Boche, C. Deppe, J. Eschner, S. Höfling, D. Meschede, P. Michler, et al., Advanced Quantum Technologies 3, 1900141 (2020), https://advanced.onlinelibrary.wiley.com/doi/pdf/10.1002/qute.201900141.
[3] M. Zopf, R. Keil, Y. Chen, J. Yang, D. Chen, F. Ding, and O. G. Schmidt, Phys. Rev. Lett. 123, 160502 (2019).
[4] J. Yang, Z. Jiang, F. Benthin, J. Hanel, T. Fandrich, R. Joos, S. Bauer, S. Kolatschek, A. Hreibi, E. P. Rugeramigabo, et al., Light: Science & Applications 13, 150 (2024), ISSN 2047-7538.
[5] C. Ma, J. Yang, P. Li, E. P. Rugeramigabo, M. Zopf, and F. Ding, Opt. Express 32, 14789 (2024). | |
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27 May 2025
Physikalisches Kolloquium
Institut für Physik 16:15 Uhr s.t., HS KPH |
| *Cancelled — postponed to winter semester 2025/26* Subir Sarkar, University of Oxford | |
In the ΛCDM cosmological model the Universe is assumed to be isotropic and homogeneous when averaged on large scales. That the Cosmic Microwave Background has a dipole anisotropy is interpreted as due to our peculiar (non-Hubble) motion because of local inhomogeneity. There must then be a corresponding dipole in the sky distribution of sources at high redshift. Using catalogues of radio sources and quasars we find that this expectation is rejected at >5σ, i.e. the distribution of distant matter is not isotropic in the 'CMB frame’. This calls into question the standard practice of boosting to this frame to analyse cosmological data, in particular to infer acceleration of the Hubble expansion rate using Type Ia supernovae, which is then interpreted as due to a Cosmological Constant Λ. We find that the inferred acceleration is anisotropic (in the direction of the CMB hotspot) and likely illusory because of our being embedded in a coherent bulk flow, rather than due to dark energy. | |
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Theorie-Palaver
Institut für Physik 14:00 Uhr s.t., Lorentz room (Staudingerweg 7, 5th floor) |
| Sulagna Bhattacharya, Tata Institute, Mumbai | |
Gravitational wave (GW) observations have opened new avenues for probing Beyond Standard Model (BSM) physics. While most detections involve typical black hole (BH) or neutron star (NS) mergers, events like GW190814, GW190425, and GW230529 observed by the LIGO-Virgo-KAGRA (LVK) collaboration include at least one compact object whose nature—either a binary neutron star (BNS) or a low-mass black hole (LMBH)—remains uncertain. One possible formation channel for such LMBHs involves dark matter (DM) capture and accumulation in NSs, leading to a collapse-induced transmutation of the NS into a BH of comparable mass.
I will discuss how DM capture in NSs can lead to the formation of LMBHs, highlighting the relevant parameter space that governs this process. I will also show how current GW observations can constrain portions of this DM parameter space. In the second part, I will focus on the gravitational waveforms of BNS mergers versus LMBH mergers, examining their distinguishing features and assessing the capability of current and future detectors to differentiate between these two scenarios. | |
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28 May 2025
PRISMA+ Colloquium
Institut für Physik 13:00 Uhr s.t., Lorentz-Raum, 05-127, Staudingerweg 7 |
| Prof. Dr. Jacqueline Keintzel, CERN, Geneva, Switzerland | |
The quest to probe the Standard Model more deeply and to search for physics beyond its current limits continues to drive the development of future particle colliders. Numerous ambitious proposals, both linear and circular designs, and lepton and hadron colliders, aim to push the frontiers of energy and luminosity to unprecedented levels. This seminar will present an overview of the main collider concepts, examining their scientific motivations, design strategies, and individual strengths. In addition, the technological challenges these proposed machines face will be discussed, along with potential synergies and complementarities among the different proposals. Slides here... | |
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03 Jun 2025
Physikalisches Kolloquium
Institut für Physik 15:30 Uhr s.t., HS KPH |
| Christian Weinheimer EARLIER at 3:30pm Coffee at 3:15pm, Universität Münster | |
Fundamental questions in astrophysics and cosmology such as the matter to antimatter asymmetry (baryon asymmetry) in the
universe or the existence of dark matter are thought to be closely linked to particle physics. For example, the baryon
asymmetry of the universe can be explained by models of leptogenesis, which require special properties of neutrinos. And
the as yet unknown dark matter presumably consists of particles that require physics beyond the standard model of
particle physics.
This question can be investigated using search and precision experiments in (astro)particle physics at low energies.
In this colloquium, this will be illustrated by three examples: the search for neutrinoless double beta decay, the direct
search for the neutrino mass and the direct search for dark matter. These searches will be explained using specific
experiments, such as the KATRIN and XENONnT experiments including their recent results,
as well as the respective perspectives for the future possibilities | |
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Theorie-Palaver
Institut für Physik 14:00 Uhr s.t., Lorentz room (Staudingerweg 7, 5th floor) |
| Davison Soper, Oregon U. | |
The cross section for an infrared safe observable in hadron-hadron collisions can be written as the convolution of parton distribution functions (PDFs) for the two hadrons and a perturbatively calculable hard scattering function, with power suppressed corrections. The arguments that this PDF factorization works at all orders of perturbation theory involves the cancellation of what are called Glauber singularities from soft gluons that interact with both hadrons. I illustrate the arguments used in a 1988 paper with Collins and Sterman by applying these arguments to graphs at the lowest order in which the Glauber problems appear. We can see in this simple example how the contributions from Glauber singularities disappear. This sort of analysis is perhaps useful for the analysis of "non-global" logarithms in certain observables. | |
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04 Jun 2025
PRISMA+ Colloquium
Institut für Physik 13:00 Uhr s.t., Lorentz-Raum, 05-127, Staudingerweg 7 |
| Prof. Dr. Livia Ludhova, FZ Jülich & JGU Mainz | |
Present Status of JUNO | |
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05 Jun 2025
Seminar über Quanten-, Atom- und Neutronenphysik (QUANTUM)
Institut für Physik 14 Uhr c.t., IPH Lorentzraum 05-127 |
| Prof. Dr. Christine Silberhorn, Universität Paderborn (Integrierte Quantenoptik) | |
Integrated Quantum Optics, Department Physics, Institute for Photonic Quantum Systems (PhoQS,), Paderborn University, 33098 Paderborn, Germany Quantum technologies promise a change of paradigm for many fields of application, for example in communication systems, in high-performance computing and simulation of quantum systems, as well as in sensor technology. Current efforts in photonic quantum science target the implementation of practical devices and scalable systems, where the realization of quantum devices for real-word deployment and controlled quantum network structures is key for many applications.
Here we present our work on three different fields in this area: non-linear integrated quantum optics, pulsed temporal modes and photonic quantum computation. | |
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10 Jun 2025
Physikalisches Kolloquium
Institut für Physik 16:15 Uhr s.t., HS KPH |
| Günter Reiss, Universität Bielefeld | |
Magnetic Heterostructures: From Sensors and Memories to Altermagnets | |
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Seminar über die Physik der kondensierten Materie (SFB/TRR173 Spin+X und SFB/TR288 Kolloquium, TopDyn-Seminar)
JGU Sonderseminar: 13:00 Uhr s.t., Noether Room (03-423) |
| Jayasimha Atulasimha, Virginia Commonwealth University | |
In a world where a single company like Google consumed more energy than a country with population of about 20 million [1] in 2019 and this is growing exponentially, it is essential to find energy efficient approaches to make our computing needs sustainable. One potential solution is the use of nanoscale magnetic computing devices. Towards this end, energy efficient approaches based on electrical field control of nanoscale magnetism are pursued in our group: (i) strain mediated switching of the magnetization of nanomagnets [2]; (ii) creation and annihilation of magnetic skyrmions using direct voltage control of magnetic anisotropy (VCMA) [3]; and more recently magnetoionic control [4]. Such nanoscale magnetic devices have application to non-volatile memory [3], hardware AI [4, 5, 6] and quantum control of spins [7,8,9].
We will discuss skyrmion mediated voltage control of nanoscale magnetization that has potential for extremely energy efficient non-volatile memory [3] and are robust to switching errors in the presence of thermal noise, material and device inhomogeneities, while scaling to lateral dimensions of 20 nm and below [3]. Furthermore, energy efficient AI hardware can be realized with nanomagnetic devices. Multi-state nanoscale domain wall racetracks can be used as highly quantized synapses in deep neural networks [5] and convolutional neural networks, with overall improvement in area, energy, and latency by 13.8, 9.6, and 3.5 times respectively [5] compared to purely CMOS implementations. Additionally, interacting nanomagnets can be used for analog [6] and digital reservoir computing [6] and long-term prediction of temporal data [6]. We will specifically discuss experimental implementation of reservoir computing with magnetoionic devices [4] that do not need conversion of signals to GHz unlike when Spin Torque Nano Oscillators (STNOs) are used.
In quantum computing, in addition to energy efficiency, one significant problem is implementing qubits in a scalable manner at temperatures of a few Kelvin. We argue that ensemble spin qubits may offer such a possibility [7]. Furthermore, by driving the magnetization of nanomagnets electrically, highly confined microwaves can be generated at the Larmor precession frequency of proximally located spins [8]. This can implement single-qubit quantum gates with fidelities approaching state-of-the-art in a scalable manner. Further confinement of microwaves using convergent-divergent skyrmion devices can implement even more localized and low footprint quantum control of spins [8]. New experimental and simulation results in these directions will be discussed [9].
References
[1] FORBES Editor’s pick, Oct 21, 2020,04:26pm EDT
[2] Nano Letters, 16, 1069, 2016; Nano Lett., 16, 5681, 2016; Appl. Phys. Lett. 121, 252401, 2022; https://arxiv.org/abs/2501.00980
[3] Nature Electronics 3, 539, 2020; Scientific Reports,11, 20914, 2021; Scientific Reports, 14, 17199, 2024
[4] https://arxiv.org/abs/2412.06964
[5] Nanotech. 31 145201, 2020, IEEE Access, 10, 84946, 2022; IEEE Trans. on Neural Networks and Learning Sys, 36, 4996, 2024.
[6] Appl. Phys. Lett. 121, 102402, 2022; Comm. Phys. 6, 215, 2023; Neuromorph. Comput. Eng. 2 044011; IEEE Access, 11,124725, 2023
[7] https://arxiv.org/abs/2503.12071
[8] Communication Physics 5, 284, 2022; Physical Phys. Rev. Applied 22, 06407, 2024.
[9] https://arxiv.org/abs/2407.14018 | |
Sonderseminar | |
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Theorie-Palaver
Institut für Physik 14:00 Uhr s.t., Lorentz room (Staudingerweg 7, 5th floor) |
| Miguel Vanvlasselaer, Brussels U., IIHE | |
In this talk, we derive the coupled dynamics between the bubble wall and the plasma from first principles using nonequilibrium quantum field theory. The commonly used equation of motion of the bubble wall in the kinetic approach is shown to be incomplete. In the language of the two-particle-irreducible effective action, the conventional equation misses higher-loop terms generated by the condensate-particle type vertices (e.g.,~ φϕχ2, where φ is the background field describing the bubble wall, ϕ the corresponding particle excitation and χ another particle species in the plasma). From the missing terms, we identify an additional dissipative friction which is contributed by particle production processes from the condensate-particle type vertices. We also show how other transmission processes beyond the 1-to-1 elementary transmission studied in the literature for ultrarelativistic bubble walls, e.g., 1-to-1 mixing and 1-to-2 transition radiation, can be understood from the kinetic approach. | |
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11 Jun 2025
PRISMA+ Colloquium
Institut für Physik 13:00 Uhr s.t., Lorentz-Raum, 05-127, Staudingerweg 7 |
| Prof. Dr. Frank Ohme, MPI for Gravitational Physics, Hannover | |
Centuries after Newton described a gravitational force, Einstein revolutionised our understanding of space, time and gravity in his general theory of relativity. Another 100 years later marked the beginning of a new era of astronomy, in which spacetime oscillations (a.k.a. gravitational waves) are used to detect the inspiral and merger of the most compact objects in the Universe. In my talk, I will review the methods and results of 10 years of gravitational-wave astronomy that saw already about 300 detections, most of them of black-hole mergers. I will discuss some insights and open questions that emerged from those observations and illustrate that Einstein's picture still holds for these most violent cosmic collisions. | |
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Seminar über die Physik der kondensierten Materie (SFB/TRR173 Spin+X und SFB/TR288 Kolloquium, TopDyn-Seminar)
JGU 13:00 Uhr s.t., tba. |
| Prof. Dr. Yaroslav Tserkovnyak, UCLA | |
In this talk, I will review two device concepts based on nonlinear dissipative magnetic dynamics. First, we revisit the problem of spin superfluidity, which has been predicted to facilitate coherent spin transport. We propose to both exhibit and exploit this elusive transport phenomenon via the "spin-superfluid quantum interference device" (spin SQUID) — inspired by its superconducting (rf SQUID) and superfluid helium (SHeQUID) counterparts. In particular, we discuss its potential electric-field sensing functionality based on the microwave response of the simplest pertinent structure: a magnetic ring with a single weak link. In the second part of the talk, we systematically address the pseudo-Hermitian physics of dynamically-coupled magnetic macrospins, with a focus on non-Hermitian mode hybridization and its potential utility as a scalable building block for dynamic Ising machines. | |
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12 Jun 2025
Seminar über Quanten-, Atom- und Neutronenphysik (QUANTUM)
Institut für Physik 14:15 Uhr s.t., IPH Lorentzraum 05-127 |
| Prof. Dr. Sven Höfling, Julius-Maximilians-Universität Würzburg | |
As high-performant sources of single photons, epitaxial quantum dots can be considered as a semiconductor launchpad for quantum photonic technologies. There is still a variety of challenges to tackle on the road to an ideal source of single or entangled photons for quantum photonic applications. Here, we present an overview of recent developments in our group on the engineering of single-photon sources for quantum photonic applications made from III-V semiconductor quantum dots grown by molecular beam epitaxy. By integrating InAs/InP quantum dots into circular Bragg grating resonators, Purcell-enhanced single-photon emission with a Purcell factor of ≈7 in the telecom C-band was achieved. Low multi-photon emission probabilities are obtained, and Hong-Ou-Mandel two-photon interference is demonstrated. By further improving the epitaxial growth, photonic design and excitation schemes, we were able to obtain record two photon interference visibilities. We furthermore report on recent progress made in our group towards deterministic generation of one-dimensional photonic cluster states directly in the telecom C-Band as a resource for quantum repeaters and quantum computers. | |
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17 Jun 2025
Physikalisches Kolloquium
Institut für Physik 16:15 Uhr s.t., Staudinger Hörsaal |
| Serge Haroche, Laboratoire Kastler Brossel, Collège de France | |
We are celebrating this year the centenary of quantum mechanics, the culmination of discoveries made at the beginning of the last century, among which Bohr's model of the hydrogen atom played an essential role. This model justified Rydberg's formula, which empirically described the spectrum of this atom and predicted the existence of highly excited atomic states with remarkable exaggerated properties (huge size of the electron orbits, long life span, intense coupling with microwave fields and very strong interactions between these atoms at quasi-macroscopic distances). The experimental study of these atoms - particularly of the circular Rydberg states of maximum angular momentum described by Bohr - began half a century ago with the development of tunable lasers. Rydberg atoms have played a central role in the development of Cavity Quantum Electrodynamics, in experiments which have tested the principles of quantum mechanics by realizing in the laboratory some of the Gedankenexperiment conceived a hundred years ago by the founders of quantum physics, among which the famous “Schrödinger cat” experiment. More recently, Rydberg atoms have been used in quantum simulation studies where, trapped in optical lattices, they are individually controlled, manipulated and detected by laser light. The physics of Rydberg atoms is thus closely associated with the history of quantum physics from its origins to its most recent developments, with the promise of more exciting advances in the years to come. | |
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Theorie-Palaver
Institut für Physik 14:00 Uhr s.t., Lorentz room (Staudingerweg 7, 5th floor) |
| Henrique Rubira, LMU München, Kavli Institute for Cosmology, Cambridge | |
Major improvements in the theoretical aspects of Cosmology have been possible in recent years due to QFT-inspired methods, such as the effective field theory of large-scale structure (EFTofLSS). In this talk, I will explore further connections between high-energy physics and cosmology. I will present a systematic approach to renormalizing the galaxy bias parameters using path integrals and a finite cutoff scale Λ. I will derive the differential equations of the Wilson-Polchinski renormalization group that describe the evolution of the finite-scale bias parameters with Λ, analogous to the β-function running in QFT. I will then discuss how the RG-flow of EFTofLSS can lead to improvements in the extraction of cosmological parameters and also serve as a tool for sanity checks. | |
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18 Jun 2025
PRISMA+ Colloquium
Institut für Physik 13:00 Uhr s.t., Lorentz-Raum, 05-127, Staudingerweg 7 |
| Dr. Thomas Siegert, University Würzburg | |
The soft gamma-ray range of MeV photons is notoriously difficult to analyse and interpret owing to strong instrumental background and large systematic uncertainties. Alas, measurements in this ‘MeV gap’ have a huge potential towards solving many of the great questions in astrophysics and cosmology. For more then two decades, the spectrometer aboard the INTEGRAL satellite, SPI, is detecting photons from 0.02 to 8 MeV with its high-purity germanium detectors for the study of accreting compact objects, pulsars, massive star groups, and supernovae and their remnants, among others. Especially the gamma-ray lines from excited nuclei and positron annihilation serve as an invaluable messenger for stellar evolution, Galactic dynamics and feedback, cosmic-ray acceleration and propagation, as well as the dark matter phenomenon. In this lecture, I will summarise how MeV observations work, what INTEGRAL has achieved during its 22-yr mission, and what will be possible with the next generation MeV telescope, COSI, the Compton Spectrometer and Imager, which NASA slated for launch in 2027. | |
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24 Jun 2025
Physikalisches Kolloquium
Institut für Physik 16:15 Uhr s.t., HS KPH |
| Cancelled — postponed to winter semester 2025/26 Nir Barnea, The Hebrew University of Jerusalem | |
Behaviour of Correlated Nucleon Pairs Inside Nuclei | |
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Theorie-Palaver
Institut für Physik 14:00 Uhr s.t., Lorentz room (Staudingerweg 7, 5th floor) |
| Louis Hamaide, INFN Naples and King's College London | |
Optomechanical sensors have seen recent innovations which make them more useful as leading detectors of ultralight dark matter. To date they remain a less-studied class of detectors among the rapidly developing field of quantum sensors, and a full study of the potential of these sensors to detect scalar, pseudoscalar and vector DM couplings is needed. After reviewing the necessary theoretical background to calculate their sensitivity, I will give some new insights into optimisation of these systems for DM detection and propose a new detector which can lead to new bounds on DM couplings, focusing on B-L vector DM as an illustration. This new setup, proposed in collaboration with the optomechanics group at UCL, is feasible with current technologies at their disposal, and can operate at the standard quantum limit (SQL). Finally I will briefly discuss the prospects of improving on these bounds by reaching SQL on resonance and other exciting near-future prospects. | |
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25 Jun 2025
PRISMA+ Colloquium
Institut für Physik 13:00 Uhr s.t., Lorentz-Raum, 05-127, Staudingerweg 7 |
| Prof. Dr. Ruth Pöttgen, Lund University, Sweden | |
Due to illness, this talk has to be re-scheduled to next semester. | |
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26 Jun 2025
GRK 2516 Soft Matter Seminar
Uni Mainz 14:30 Uhr s.t., Minkowski Room, 05-119, Staudingerweg 7 |
| Friederike Schmid, JGU, Physics | |
TBA | |
| at Zoom | |
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GRK 2516 Soft Matter Seminar
Uni Mainz 15:00 Uhr s.t., Minkowski Room, 05-119, Staudingerweg 7 |
| Thomas Speck, University of Stuttgart, Physics | |
TBA | |
| at Zoom | |
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01 Jul 2025
Physikalisches Kolloquium
Institut für Physik 16:15 Uhr s.t., HS KPH |
| Dennis Lehmkuhl, Universität Bonn | |
Philosophy of Physics | |
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Theorie-Palaver
Institut für Physik Sonderseminar: 14:00 Uhr s.t., Lorentz room (Staudingerweg 7, 5th floor) |
| Guillem Domènech, Leibniz U., Hannover | |
The evolution of density fluctuations in the early universe inevitably generates gravitational waves. Cosmic microwave background observations measured such primordial density fluctuations on the largest scales in our universe (> Mpc). These large-scale fluctuations began their evolution days or years after the Big Bang. How was the universe at earlier times and on smaller scales? At the moment, we do not know much. But gravitational wave observations will provide new information in the next decades. In this talk, I will provide an overview of the so-called induced gravitational waves and how they can be used to probe the presence of primordial black holes. I will place emphasis on the effect of particle interactions on the resulting gravitational wave spectrum. On the occasion of the MITP conference, I will briefly discuss the implications of detecting high-frequency GWs for the primordial black hole scenario. | |
Sonderseminar | |
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Theorie-Palaver
Institut für Physik 16:00 Uhr s.t., THEP room (Staudingerweg 7, 5th floor, R. 05-427) |
| Prof. Andre Leclair, Cornell University | |
We consider 2 coupled Higgs doublets which transform in the usual way under SU(2)⊗U(1). By constructing marginal operators which satisfy an operator product expansion based on the SU(2) Lie algebra, we can obtain a rich pattern of renormalization group (RG) flows which includes lines
of fixed points and more interestingly, cyclic RG flows which are unavoidable in this model. The hamiltonian is pseudo-hermitian, $H^\dagger = K H K$ with $K$ unitary satisfying $K^2 = 1$, thus the model is non-unitary. The hamiltonian still has real eigenvalues, but the non-unitarity is manifested in negative norm states. One can use the operator K to define projection operators onto positive norm states, and in this sub-Hilbert space the time evolution is unitary with positive probabilities. Upon spontaneous symmetry breaking, the Higgs fields have an infinite number of vacuum expectation
values $v_n$ which satisfy “Russian Doll” scaling $v_n \sim e^{2n \lambda}$ where n= 1,2,3,...and $\lambda$ is the period of one RG cycle which is an RG invariant. We speculate that this Russian Doll RG flow can perhaps resolve the so-called hierarchy problem and may shed light on the origin of “families” in the Standard Model of particle physics | |
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02 Jul 2025
PRISMA+ Colloquium
Institut für Physik 13:00 Uhr s.t., Lorentz-Raum, 05-127, Staudingerweg 7 |
| Prof. Dr. Chen Ji, Wuhan University, China | |
Experiments at rare isotope beam facilities have revealed 'halo nuclei' at the edge of the nuclear chart, which are exotic systems featuring a molecular-like structure of a core and halo nucleons. These nuclei play a crucial role in the astrophysical synthesis of elements. Effective field theory (EFT), combined with a nuclear cluster model, provides a robust framework for accurately describing the structure and dynamics of these halos. This talk will cover the fundamentals of halo EFT and demonstrate its application to key observables, including binding energies and radii, as well as essential reaction processes such as photo-disintegration and radiative nucleon captures Slides here... | |
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03 Jul 2025
GRK 2516 Soft Matter Seminar
Uni Mainz 14:30 Uhr s.t., Minkowski Room, 05-119, Staudingerweg 7 |
| Katrin Amann-Winkel, MPI-P | |
TBA | |
| at Zoom | |
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GRK 2516 Soft Matter Seminar
Uni Mainz 15:00 Uhr s.t., Minkowski Room, 05-119, Staudingerweg 7 |
| Pol Besenius, JGU, Chemistry | |
TBA | |
| at Zoom | |
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08 Jul 2025
Physikalisches Kolloquium
Institut für Physik 16:15 Uhr s.t., HS KPH |
| Volker Springel, Max Planck-Institut für Astrophysik, Garching | |
Numerical calculations of cosmic structure formation have become a powerful tool in astrophysics. Starting right after the Big Bang, they are not only able to accurately predict the dark matter backbone of the cosmic web far into the non-linear regime, but are also capable of following baryonic physics with rapidly improving fidelity. In my talk, I will review the methodology and selected results of recent structure formation simulations that follow large parts of the observable universe. I will discuss some of the primary challenges in modelling strong, scale-dependent feedback processes that regulate star formation in galaxies, and highlight the important role played by supermassive black holes in galaxy formation. I will also discuss extremely large simulations and describe how they help to make reliable predictions for the impact of baryons and massive neutrinos on cosmological observables, effects that need to be understood to make full use of upcoming new survey data. The simulation results also shed light on cosmic reionization and magnetic field amplification during non-linear structure formation. Finally, I will highlight some of the methodological and technical challenges involved in obtaining future multi-physics, multi-scale simulations that aim for more accurate predictions. | |
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Theorie-Palaver
Institut für Physik Sonderseminar: 14:00 Uhr s.t., Lorentz room (Staudingerweg 7, 5th floor) |
| Antonio Iovino, New York U., Abu Dhabi | |
The existence of primordial black holes can be probed through the gravitational waves generated during their formation and subsequent evolution. In this talk, we will explore different frequency ranges and the corresponding experiments designed to test their existence. We will cover the spectrum from ultra-low-frequency gravitational waves—targeted by future missions such as LiteBIRD—to current experiments using pulsar timing arrays and the LIGO-Virgo-KAGRA network, as well as upcoming efforts in the ultra-high-frequency domain. | |
Sonderseminar | |
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09 Jul 2025
PRISMA+ Colloquium
Institut für Physik 13:00 Uhr s.t., Lorentz-Raum, 05-127, Staudingerweg 7 |
| Carlos Tamarit Degenhardt, THEP, JGU Mainz | |
The early universe likely underwent a series of phase transitions as it expanded and cooled from an initially hot, dense state. Among these, first-order phase transitions --proceeding through the nucleation and expansion of bubbles-- are particularly interesting due to their potential cosmological implications, which include gravitational wave production and the possibility to generate the baryon asymmetry through the mechanism of electroweak baryogenesis. In this talk I will review the theoretical framework used to study such transitions and discuss recent progress on understanding bubble velocities and CP-violating effects relevant for electroweak baryogenesis. Slides here... | |
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10 Jul 2025
Seminar über Quanten-, Atom- und Neutronenphysik (QUANTUM)
Institut für Physik 14:15 Uhr s.t., IPH Lorentzraum 05-127 |
| Prof. Dr. Friedemann Reinhard, Universität Rostock | |
Diamond quantum sensors for magnetic fields have transformed several areas of science, most prominently magnetic resonance and magnetic field imaging at the micro- and nanoscale. However, these breakthroughs have largely remained limited to specialized laboratories. I will present two lines of research of our laboratory to change this state of affairs and significantly simplify the use of diamond quantum sensors.
One direction concerns scanning probe imaging, where we have developed a simplified approach to scanning probe positioning. While conventional setups image magnetic fields by scanning a nanofabricated diamond tip hosting a single NV center across a sample, we developed a setup where we can scan an extended (10 µm to mm) bulk diamond in 10 nm-scale proximity of a sample, using interferometric alignment to maintain the sensor perfectly parallel to the sample. Beyond a technical simplification, this approach opens the door to massively parallel scanning probe microscopy using multiple NV centers, as well as to novel plasmonic near-field microscopes.
Another direction concerns the electric readout of large ensembles of NV center spins, as they might find application in large-scale commercial devices like gyroscopes or magnetic field sensors. Here, we have shown in recent research that readout in a microwave cavity is remarkably competitive with more established optical readout for large ensembles, and provides a straightforward all-electric way to integrate diamond spin sensors into microfabricated circuits. | |
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15 Jul 2025
Physikalisches Kolloquium
Institut für Physik 16:15 Uhr s.t., HS KPH |
| Livia Ludhova, GSI Darmstadt/JGU Mainz | |
In this inaugural lecture, I invite you on a journey across six continents, each representing a chapter in my scientific life and my contributions to experimental neutrino physics.
Europe marks my journey toward the research I pursue today—from academic studies through early work in exotic atom spectroscopy, and into the world of neutrino physics. I stay grounded in Europe, having recently joined Johannes Gutenberg University Mainz, where I’m thrilled to be part of a vibrant neutrino physics community.
Africa represents the Sun—radiant in both beauty and intensity—and solar neutrinos, born in the Sun’s core, lie at the core of my scientific work. My journey with the Borexino experiment spanned from the beginning to the end of its data taking, culminating in the precision spectroscopy of pp-chain neutrinos and the groundbreaking detection of CNO-cycle neutrinos.
The Americas, shaped over eons by powerful geological processes, connect to my background in geology and its unexpected link to neutrino physics through geoneutrino research. In Borexino, we succeeded in observing geoneutrinos—a powerful tool for understanding Earth's energetics and formation processes.
Asia, fast-moving and future-focused, represents the JUNO experiment in China—the main project of my research group. Based on the same liquid scintillator technology as Borexino but scaled up by a factor of 70, JUNO stands out as a unique next-generation neutrino experiment, now in its commissioning phase. It will be central to my research in the coming years, allowing me to apply years of experience toward discoveries across multiple scientific goals.
Australia, geographically remote yet globally connected, symbolizes the importance of collaboration and interdisciplinarity in neutrino physics. My journey—from geology to neutrino research—taught me the value of crossing scientific boundaries. At Mainz, the PRISMA++ Cluster of Excellence offers a strong platform for scientific integration.
Antarctica, like the dream-fulfilling sailing journey to its icy shores, symbolizes the vision and determination that drive us—from personal goals to ambitious scientific quests.
Through this world tour, I share not only my research but also how science—like travel—thrives on curiosity, courage, and the pursuit of the unknown, exactly where ancient maps warned: hic sunt leones. | |
Inaugural Lecture |
16 Jul 2025
PRISMA+ Colloquium
Institut für Physik 13:00 Uhr s.t., Lorentz-Raum, 05-127, Staudingerweg 7 |
| Prof. Dr. Florian Bernlochner, University Bonn | |
Status & Outlook of Belle II and some fun with Neutrinos
The Belle II experiment is preparing for an intensive seven-month data-taking run beginning in November 2025, marking the next major step in our quest to uncover physics beyond the Standard Model. Through high-precision studies of heavy-flavor decays, tau decays, and dedicated searches for light, feebly interacting particles, Belle II targets some of the most pressing open questions in fundamental physics. While the Large Hadron Collider (LHC) has discovered the Higgs boson, it has so far not revealed additional new particles that could explain the dominance of matter over antimatter, the nature of dark matter, the origin of neutrino masses, or the intricate features of strong interactions. Belle II, operating at the SuperKEKB accelerator in Tsukuba, Japan, offers a complementary approach by recording an unprecedented sample of beauty- and charm-quark decays in the clean environment of electron–positron collisions, with data taking planned through the 2040s. Following the recent long shutdown and a successful upgrade of the vertex detector, the upcoming run will be an important milestone to push forward precision tests of the Standard Model. I will also briefly highlight the FASER experiment at CERN, which complements Belle II by probing forward physics at the LHC, including neutrino interactions and searches for long-lived particles. | |
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17 Jul 2025
Seminar über Quanten-, Atom- und Neutronenphysik (QUANTUM)
Institut für Physik 14:15 Uhr s.t., IPH Lorentzraum 05-127 |
| Prof. Dr. Stefanie Barz, University of Stuttgart Institute for Functional Matter and Quantum Tech | |
I will explore various facets of photonic quantum systems and their application in photonic quantum technologies. I will start with quantum interference, a key element in photonic quantum technologies. I will then discuss photonic quantum computing, specifically focusing on the building blocks of photonic quantum computers. I will explore photonic quantum networks, covering both hardware aspects and applications. Finally, I will outline how photonic integration facilitates the scalability of these systems and discuss the associated challenges. | |
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zukünftige Termine
24 Jul 2025
Seminar über Quanten-, Atom- und Neutronenphysik (QUANTUM)
Institut für Physik 14:15 Uhr s.t., IPH Lorentzraum 05-127 |
| Dr. Christian Schmiegelow, LIAF Instituto de Física de Buenos Aires | |
In this talk, I will address two topics. I will begin by reviewing the interaction between structured light and matter, providing the necessary context to understand one of our most recent experiments, in which we measured the rotational Doppler effect—a Doppler shift that is sensitive to the direction of motion of an object transverse to the probing beam. This elusive effect was predicted several years ago, but until now, there had been no clear experimental confirmation of its existence. Our experiments clearly show that its physical properties, although counterintuitive, are as expected, and they enable the observation of even more exotic phenomena, such as the so-called "super kicks", where a single photon can transfer more momentum to an atom than ℏk.
After that, I will present a new series of experiments aimed at improving current methods for laser cooling of solids. I will explain the principles of anti-Stokes cooling, recent advances, and the perspectives for the coming years. | |
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20 Nov 2025
Seminar über Quanten-, Atom- und Neutronenphysik (QUANTUM)
Institut für Physik 14:15 Uhr s.t., IPH Lorentzraum 05-127 |
| Prof. Dr. Eugene Polzik, Niels Bohr Institute, Copenhagen, Danemark | |
TBA | |
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