Theorie Palaver

Programm für das Wintersemester 2023/2024

Tuesdays, 14:00 Uhr s.t.

Institut für Physik
Lorentz room (Staudingerweg 7, 5th floor)

24.10.23Benoit Assi, Fermilab
The geometry underlying field space plays a pivotal role in governing on-shell scattering amplitudes. In this talk, we present a comprehensive geometric description of effective field theories, building upon prior work involving scalars and gauge fields, and further extending it to fermions. This novel field-space geometry not only offers a systematic reorganization but also significantly streamlines the computation of quantum loop corrections. Capitalizing on this framework, we attain the fermion loop contributions to the renormalization group equations for bosonic operators within the Standard Model Effective Field Theory, covering up to mass dimension eight.
14:00 Uhr s.t., Lorentz room (Staudingerweg 7, 5th floor)

31.10.23Meet and Greet, -
14:00 Uhr s.t., Lorentz room (Staudingerweg 7, 5th floor)

07.11.23Encieh Erfani, JGU Mainz
In this presentation, I will elucidate the mechanisms behind Primordial Black Hole formation, discuss their potential role as candidates for dark matter, explore their significance as gravitational wave sources, and delve into the methodologies employed for their detection.
14:00 Uhr s.t., Lorentz room (Staudingerweg 7, 5th floor)

14.11.23Helena Kolešová, University of Stavanger
Taking axion inflation as an example, we study the evolution of a non-Abelian dark sector coupled to the inflaton for different choices of the confinement scale. Gravitational wave signals could be in principle generated due to a confinement phase transition or fluctuations in the thermal plasma, however, these signals might be strongly suppressed due to the presence of an early matter-dominated era. We also study the reheating of Standard Model fields and explore the possibility of glueball dark matter within this scenario.
14:00 Uhr s.t., Lorentz room (Staudingerweg 7, 5th floor)

21.11.23Maeve Madigan, Heidelberg U.
The Standard Model Effective Field Theory (SMEFT) provides a powerful theoretical framework for interpreting subtle deviations from the Standard Model and searching for heavy new physics at the LHC. Accurate interpretations of LHC data, however, rely on the precise knowledge of the proton structure in terms of parton distribution functions (PDFs). In this seminar, I will discuss the interplay between PDFs and the search for new physics. I will showcase a scenario for the High-Luminosity LHC in which the PDFs may completely absorb such signs of new physics, thus biasing theoretical predictions and interpretations. To address this challenge, I will present a simultaneous determination of PDFs and the SMEFT using the SIMUnet methodology. This approach integrates both PDF and SMEFT determinations into a single, coherent framework, making possible an assessment of the regions of parameter space in which the interplay is most phenomenologically relevant, both at the LHC and HL-LHC.
14:00 Uhr s.t., Lorentz room (Staudingerweg 7, 5th floor)

28.11.23Stefano De Angelis, IPhT, Saclay
In the first part of the seminar, I will review some recent progress made using modern on-shell techniques to understand (relativistic) EFTs and uncover hidden structures, with a particular focus on the SMEFT (from a purely on-shell construction of EFTs to selection rules in cross-section and RG equations). Motivated by this recent progress, in the second part, I will present a new on-shell formula for the matching of ultraviolet models featuring massive states onto their massless effective field theory. This formula is based on a dispersion relation in the space of complex momentum dilations to capture, in a single variable, the relevant analytic structure of scattering amplitudes at any multiplicity.
14:00 Uhr s.t., Lorentz room (Staudingerweg 7, 5th floor)

05.12.23Maura Ramirez Quezada, JGU Mainz
In this talk, I'll explore the potential of using white dwarfs as cosmic laboratories to investigate hidden interactions beyond the Standard Model. My focus will be on the cooling process of white dwarfs, specifically through neutrino emission, and investigate the impact of a dark photon in a three-portal model on the neutrino emission during white dwarf cooling.
14:00 Uhr s.t., Lorentz room (Staudingerweg 7, 5th floor)

07.12.23Kristina Giesel, FAU Erlangen
Accessing the physical sector in models of quantum gravity is on the one hand a challenge, but on the other hand also an important step to be able to analyse and test such models. One way to complete the quantisation programme in loop quantum gravity is to choose dynamical reference systems so-called matter or geometric clocks for which Dirac observables can be constructed in the framework of the relational formalism. The quantisation step then consists in finding representations for the corresponding algebra of Dirac observables that allow one to quantise the dynamics as well. In this way, one obtains an observer-dependent quantum field theory. We will give a brief overview of the existing models and discuss their similarities and differences. Finally, we will discuss examples for investigating some physical properties of models formulated with a particular choice of clocks in cosmology and open quantum systems in which gravitationally induced decoherence is present.
10:30 Uhr s.t., Lorentz room (Staudingerweg 7, 5th floor)

12.12.23Gael Finauri, TU München
Light-cone distribution amplitudes (LCDAs) frequently arise in factorization theorems involving light and heavy mesons. The QCD LCDA for heavy mesons includes short-distance physics at energy scales of the heavy quark mass. In this talk I will explain how to achieve the separation of this perturbative scale from the purely hadronic effects by expressing the QCD LCDA as a convolution of a perturbative « jet » function with the universal, quark-mass independent HQET LCDA. This factorization allows to efficiently resum large logarithms between Lambda QCD and m_Q as well as between m_Q and the scale of the hard process in the production of boosted heavy mesons at colliders. As an application I will present updated theoretical predictions for the brancing ratio of W -> B \gamma.
14:00 Uhr s.t., Lorentz room (Staudingerweg 7, 5th floor)

19.12.23Andrea Sanfilippo, TU München
The description of light and massless scalar fields in an inflationary spacetime is of phenomenological interest, as they provide compelling candidates for the inflaton field. During most of the inflationary epoch, the spacetime can be approximated by the de Sitter spacetime, and the observables of interest are in-in correlation functions of fields in de Sitter space, evaluated at late times. However, the computation of these quantities is challenging, particularly when loop corrections are taken into account. In this talk, I will discuss the recently proposed Soft de Sitter Effective Theory (SdSET) as an avenue to address these difficulties. I will then show how the Method of Regions can be used as a powerful tool to construct the late-time expansion of in-in correlators, as well as to gain further insight into the structure of SdSET.
14:00 Uhr s.t., Lorentz room (Staudingerweg 7, 5th floor)

09.01.24Zeno Capatti, U. Bern
In this talk, I will review the main aspects of three-dimensional approaches to the computation of Feynman diagrams and of the Local Unitarity formalism. I will start by discussing the Cross-Free Family representation, which allows for a systematic analysis of the singularities of Feynman diagrams. I will then introduce the Local Unitarity framework, in which interference diagrams are combined, through a generally-applicable mapping of the phase-space measure, to give locally finite cross-sections. Finally, I will discuss the extension of the Local Unitarity formalism to processes with initial state singularities, which will allow me to discuss the role of spectator particles and higher-multiplicity initial-state partonic configurations in the cancellation and factorisation of singularities.
14:00 Uhr s.t., Lorentz room (Staudingerweg 7, 5th floor)

16.01.24Álvaro Pastor Gutiérrez, MPIK Heidelberg
While the Standard Model of particle physics has been extremely successful in predicting experimental results, it still leaves us with unanswered questions about dark matter, the imbalance between matter and antimatter, and the emergence of fundamental scales. In this talk, I will outline our initial efforts to explore strong new physics scenarios using the non-perturbative functional renormalisation group. I will begin by introducing the flow equation and applying it to the Standard Model, thereby uncovering previously uncharted high-energy phases in the Higgs potential. The second part of the talk will focus on a comprehensive study of (quasi-)conformal “Technicolour” theories, aiming to identify Higgs-like bound states and detectable dark sectors. To achieve this, we will employ bosonisation techniques, which provide valuable insights into the properties of dynamically emergent bound states. I will conclude with a specific case study addressing the flavour puzzle within the framework of fundamental partial compositeness.
14:00 Uhr s.t., Lorentz room (Staudingerweg 7, 5th floor)

23.01.24Daniel Schmitt, Frankfurt U.
Theories beyond the Standard Model (BSM) with classical scale invariance predict an intriguing thermal history of the early Universe. Due to the absence of dimensionful terms at tree level in these models, the electroweak phase transition (EWPT) can be significantly delayed, inducing a period of thermal inflation supercooling the Universe. The exit from this supercooled state can then be triggered via different mechanisms, depending on the model parameter space. In the first part of my talk, I will discuss the end of supercooling via a strong, first-order QCD chiral phase transition. I will outline how the associated gravitational wave (GW) production can be studied within effective QCD theories, with a particular focus on the effect of thermal inflation on the strongly coupled dynamics. In the second part, I will present an additional option to realize the exit from supercooling: a tachyonic phase transition. Here, the SM quark condensates source an exponential amplification of BSM scalar fields, generating a unique GW background detectable by future observatories.
14:00 Uhr s.t., Lorentz room (Staudingerweg 7, 5th floor)

30.01.24Maria Ramos, IFT Madrid
Singlet scalars, namely axion-like particles (ALPs), are among the most promising candidates of new physics. Standard (minimal) assumptions in the study of these particles might however hide a large landscape of solutions to different puzzles in the Standard Model, which can limit our discovery potential. In the first part of the talk, I will consider the impact of scalar mixing in the standard axion mechanism to solve the strong CP problem. I will show that the canonical axion mass-scale relation can be modified within QCD and multiple signals may be required to reconstruct the full solution to the strong CP problem, constrained by a precise sum rule. In the second part of the talk, I will discuss the impact of operator mixing, via RGEs, in the ALP parameter space. I will specially focus on shift-breaking and CP violating effects, and I will discuss some phenomenological applications.
14:00 Uhr s.t., Lorentz room (Staudingerweg 7, 5th floor)

06.02.24Filippo Sala, U. Bologna
I will show how first order phase transitions (PT) in the early universe, with relativistic bubble walls, constitute particle accelerators and colliders via the dense shell of particles that they necessarily accumulate. These `bubbletrons' offer novel opportunities of observational access to very high energy scales, in addition to the gravitational waves from the PT. As three examples, I will discuss: i) non-adiabatic production of ZeV dark matter which is hot enough to leave an imprint in the matter power spectrum; ii) production of relics beyond the GUT scale without the need for the universe to ever reach those temperatures; iii) realization of testable baryogenesis and leptogenesis down to the TeV scale. In passing I will mention open questions about the physics of particle shells at bubble walls, and their potential far-reaching implications.
14:00 Uhr s.t., Lorentz room (Staudingerweg 7, 5th floor)

Koordination: Kontakt:

Max Ferré

Anne Galda

Sebastian Schenk