Physikalisches Kolloquium

Programm für das Sommersemester 2022

Tuesdays, 16 Uhr c.t.

Institut für Kernphysik

19.04.22Piet O. Schmidt, MPI für Dynamik und Selbstorganisation
Highly charged ions (HCI) have many favorable properties for tests of fundamental physics and as potential next-generation optical atomic frequency standards. However, up until recently the most accurate laser spectroscopy on any HCI was performed on the 17 Hz wide fine-structure transition in Ar13+ with 400 MHz resolution, lagging almost twelve orders of magnitude behind state-of-the-art optical clocks. We present the first coherent laser spectroscopy of an HCI using techniques developed in the context of quantum information processing with trapped ions. A novel quantum algorithmic cooling scheme has been developed and implemented, which reduces motional shifts to below the 10-18 level. We have performed an absolute frequency measurement, including a full error budget for the Ar13+ HCI clock, which demonstrates that HCI optical clocks with systematic uncertainty below 10-18 become feasible. Finally, prospects for 5th force tests based on isotope shift spectroscopy of Ca+/Ca14+ isotopes and the high-sensitivity search for a variation of the fine-structure constant using HCI will be presented. This work paves the way towards optical clocks based on highly charged ions with a high sensitivity to a change in fundamental constants and other tests of beyond standard model physics.
16:15 Uhr s.t., HS KPH

26.04.22Yuri Litvinov, GSI Darmstadt
The storage of freshly produced radioactive particles in a storage ring is a straightforward way to achieve the most efficient use of the rare species as it allows for using the same secondary ion multiple times. Employing storage rings for precision physics experiments with highly-charged ions (HCI) at the intersection of atomic, nuclear, plasma and astrophysics is a rapidly developing field of research. The number of physics cases is enormous. The focus here will be on the most recent highlight results achieved within FAIR-Phase 0 research program at the ESR. First, the measurement of the bound-state beta decay of fully-ionized 205Tl was proposed about 35 years ago and was finally accomplished in 2020. Here, the ESR is presently the only instrument enabling precision studies of decays of HCIs. Such decays reflect atom-nucleus interactions and are relevant for atomic physics and nuclear structure as well as for nucleosynthesis in stellar objects. Second, the efficient deceleration of beams to low energies enabled studies of proton-induced reactions in the vicinity of the Gamow window of the p-process nucleosynthesis. After proof-of-principle studies on stable 124Xe ions, proton capture reaction on short-lived 118Te was successfully measured in the ESR. Here, the well-known atomic charge exchange cross-sections are used to constrain poorly known nuclear reaction rates. The performed experiments will be put in the context of the present research programs at GSI/FAIR and in a broader, worldwide context, where, thanks to fascinating results obtained at the presently operating storage rings, a number of new exciting projects is planned.
16:15 Uhr s.t., HS KPH

03.05.22Stefano Vitale, University of Trento
LISA is a space-borne gravitational wave (GW)observatory under development by the European Space Agency (ESA). It aims at the GW spectrum between a few tens of micro-Hz and a fraction of a Hz, which cannot be accessed by ground-based detectors. Such frequency range gives access to million solar mass sources at cosmological distances, and to non-transient GW astronomy of our Galaxy. LISA has been preceded by a precursor mission, LISA Pathfinder, that has successfully demonstrated the necessary space-time metrology. The talk will review the science and achievements of LISA Pathfinder, the status of LISA, and some recent highlights on LISA science. Join Zoom Meeting Meeting ID: 934 7730 8509 Passcode: physics One tap mobile +496971049922,,93477308509#,,,,*4055134# Germany +496938079883,,93477308509#,,,,*4055134# Germany Dial by your location +49 69 7104 9922 Germany +49 69 3807 9883 Germany +49 69 3807 9884 Germany +49 69 5050 0951 Germany +49 69 5050 0952 Germany +49 695 050 2596 Germany Meeting ID: 934 7730 8509 Passcode: 4055134 Find your local number:
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16:15 Uhr s.t., at Recording of the presentation

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10.05.22Dr. Sebastian Raeder, GSI Helmholtzzentrum für Schwerionenforschung GmbH
The quest for long-lived isotopes of superheavy elements on the so-called "island of stability" has motivated interdisciplinary research in this area for almost 50 years. The heaviest elements are of interest to nuclear and atomic physicists as well as to chemists due to their peculiar properties. While nuclear shell structure effects are responsible for their very existence stabilizing them against spontaneous disintegration, the structure of their electronic shells is affected by strong relativistic effects leading to different atomic and chemical properties compared to their lighter homologs. The atomic structure can be probed by laser spectroscopy which is a powerful tool to unveil fundamental atomic and nuclear properties. The lack in atomic information on the heavy element of interest, the low production rates, and the rather short half-lives make experimental investigations challenging and demand very sensitive experimental techniques. Recent results with dedicated experimental investigations were obtained for fermium (Fm, Z=100) and nobelium (No, Z=102) isotopes which will be discussed together with the perspectives for laser spectroscopy investigations in even heavier elements.
16:15 Uhr s.t., HS KPH

17.05.22Heino Falcke, University of Radbourg
The inside of black holes is shielded from observations by an event horizon, a virtual one-way membrane through which matter, light and information can enter but never leave. This loss of information, however, contradicts some basic tenets of quantum physics. Does such an event horizon really exist? What are its effects on the ambient light and surrounding matter? How does a black hole really look? Can one see it? Recently we have made the first image of a black hole and detected its dark shadow in the radio galaxy M87 with the global Event Horizon Telescope. Detailed supercomputer simulations faithfully reproduce these observations. Simulations and observations together provide strong support for the notion that we are literally looking into the abyss of the event horizon of a supermassive black hole. The talk will review the results of the Event Horizon Telescope, the nature and meaning of the black hole shadow, its scientific implications and future expansions of the array.
16:15 Uhr s.t., HS KPH

24.05.22Mirjam Cvetic, University of Pennsylvania, USA
In the past decades, String Theory has emerged as the prime candidate for quantum unification of electromagnetic, nuclear, and weak forces with gravitational ones It has shed light on important fundamental questions of theoretical physics, such as the microscopic structure of black holes and the geometric origin of particle physics. We review these developments, such as the introduction of extended objects - Dirichlet branes - and highlight the important geometric role these objects play in deriving the Standard Model of particle physics and the microscopic structure of black holes. We also highlight progress made in deriving particle physics from F-theory, a geometric domain of string theory at finite string coupling, and recent systematic exploration of the landscape of the quadrillion Standard Models with three families of quarks and leptons.
16:15 Uhr s.t., HS KPH

31.05.22Karin Schönning, University of Uppsala
The world around us consists of protons and neutrons – tightly bound quark systems that just like other hadrons are confined by the strong interaction. The processes occur at distances corresponding to a femtometer, i.e. 10-15 m, and generate almost 99% of the visible mass of the Universe. To describe these interactions quantitatively, belong to the most challenging problems in contemporary physics. Hyperons – quark triplets just like the protons but containing at least one heavier strange or charm quark – can shed new light on this puzzle. Being unstable, hyperons reveal through their decays more about their inner properties than protons. In particular, the hyperon spin can be traced in weak, parity violating decays. This feature makes hyperons a powerful diagnostic tool. In this talk, I will demonstrate how spin polarised and quantum entangled strange hyperons can be exploited to measure their structure and size at the femtometer scale. I will also present recent measurements from the BESIII experiment in China and discuss future opportunities offered by facilities world-wide.
16:15 Uhr s.t., HS KPH

07.06.22Ramin Golestanian, MPI Göttingen
There are many ways to study life, and one that is particularly appealing to physicists is regarding it as self-organized active soft matter that is away from equilibrium ``just the right way’’. In this Colloquium, I will discuss this notion, and provide a number of examples of how we can begin to put together simple systems - from basic ingredients that we fully understand - that would exhibit the kind of active behaviour we find in living systems. In particular, I will discuss the general class of chemical activity both as the source of non-equilibrium drive and the underlying mechanism for self-organization. Cells and microorganisms produce and consume all sorts of chemicals, from nutrients to signalling molecules. The same happens at the nanoscale inside cells themselves, where enzymes catalyze the production and consumption of the chemicals needed for life. In this colloquium, I will discuss a generic mechanism by which such chemically-active particles, be it cells or enzymes or engineered synthetic colloids, can "sense" each other and ultimately self-organize in a multitude of ways. A peculiarity of these chemical-mediated interactions is that they break action-reaction symmetry: for example, one particle may be repelled from a second particle, which is in turn attracted to the first one, so that it ends up "chasing" it. Such chasing interactions allow for the formation of large clusters of particles that "swim" autonomously. Regarding enzymes, we find that they can spontaneously aggregate into clusters with precisely the right composition, so that the product of one enzyme is passed on, without lack or excess, to the next enzyme in the metabolic cascade. Finally, I will discuss how breaking the action-reaction symmetry can allow a system described by two scalar fields to exhibit spontaneous breaking of time translation, time-reversal, space translation, and polar symmetries.
16:15 Uhr s.t., HS KPH

14.06.22Andrea Vinante, University of Trento
Levitated micro/nanoparticles are an excellent platform for very sensitive table-top mechanical experiments in the context of fundamental and quantum physics. Compared to conventional mechanical systems, they offer a higher degree of isolation from the environment and higher tunability. Levitated ferromagnets offer the additional benefit of being extremely sensitive to magnetic fields and rotations, suggesting a number of applications in the context of magnetic field sensing and fundamental physics. I will report on our efforts to levitate micromagnets by Meissner effect in a gravitational-superconducting trap, using SQUIDs as motion detectors. Preliminary measurements show that levitation can be realized in good agreement with the Meissner effect, with ultralow damping rate of rotational and translational modes in the range of microHz. I will discuss some possible applications, focusing on tests of wave function collapse models [1], exotic interactions beyond the standard model and magnetometry. Remarkably, a torque sensor based on a levitated micromagnet is expected to overcome the Standard Quantum Limit on magnetometry, and to surpass by orders of magnitude the Energy Resolution Limit, often proposed as a benchmark for quantum magnetometers. This goal may be achieved not only in the gyroscopic atom-like regime as previously argued, but also in the librational trapped regime [2]. [1] A. Vinante et al, Narrowing the Parameter Space of Collapse Models with Ultracold Layered Force Sensors, Phys. Rev. Lett. 125, 100404 (2020). [2] A. Vinante et al, Surpassing the Energy Resolution Limit with ferromagnetic torque sensors, Phys. Rev. Lett. 127, 070801 (2021).
16:15 Uhr s.t., HS KPH

21.06.22Dirk Uwe Sauer, RWTH of Aachen
Die netto CO2-Emissionen sollen in Deutschland bis 2045 auf Null gesenkt werden. Andere Ländern haben sich zum Schutz des Klimas auf ähnliche Ziele verpflichtet. Der Mobilitätssektor trägt in Deutschland mit rund 20% zu den Gesamtemissionen bei und hat anders als die meisten anderen Sektoren seit 1990 keine signifikanten Reduktionen zu verzeichnen. Neben Anstrengungen das Verkehrsaufkommen z.B. durch Verlagerung vom Auto auf die Schiene, den ÖPNV oder das Fahrrad zu verringern, sind elektrische Antriebskonzepte ein technisch realistischer Weg, der inzwischen auch mit Nachdruck weltweit in der Automobilindustrie verfolgt wird. In PKW setzt sich aktuell weltweit das Konzept des batterieelektrischen Fahrzeugs durch. Entsprechend ist die Frage, wie der Stand der Batterietechnik ist, welche Materialsysteme aktuell und in absehbarer Zeit zum Einsatz kommen, wie es um die Sicherheit der Batterien und wie es um die Rohstoffverfügbarkeiten bestellt ist. Gleichzeitig steigt der Speicherbedarf auch im Stromsystem, um die stark fluktuierende Stromerzeugung aus Windkraft- und Photovoltaikanlagen zu vergleichmäßigen. Auch hier werden in großem Umfang Batteriespeicher zum Einsatz kommen, an die aber andere Anforderungen als im Mobilitätsbereich gestellt werden. Diskutiert werden auch die Aussichten von Batterietechnologien, die heute noch nicht in großem Umfang kommerziell eingesetzt werden und die Rolle von Wasserstoff und seinen Derivaten im Mobilitätsbereich.
16:15 Uhr s.t., HS KPH

28.06.22Markus Rex, AWI Potsdam
Frozen at the North Pole - Expedition to the Epicenter of Climate Change It was the largest expedition to the Arctic ever. In October 2019, the research icebreaker “Polarstern” allowed itself to be frozen solid in the Arctic sea ice in order to drift through the central Arctic for an entire year powered only by the natural flow of the arctic ice. Supported by six other ships as well as airplanes and helicopters, this is the first time that a modern research icebreaker vessel has reached the immediate vicinity of the North Pole in winter. Following in the footsteps of Fridtjof Nansen's historic research expedition from 1893-1896, the scientists explored the North Pole in greater detail than ever before, despite extreme cold, Arctic storms, an ever-changing ice landscape and the unprecedented challenges posed by the Corona pandemic. They achieved groundbreaking observations of climate processes in the central Arctic. This will enable them to better understand and predict the climate system. Project and expedition leader Markus Rex reports on the dramatic climate change in the Arctic and gives an insight into the process and the first results of this unique expedition.
16:15 Uhr s.t., HS KPH


05.07.22Luciano Rezzolla, University of Frankfurt
Neutron stars: from macroscopic collisions to microphysics I will argue that if black holes represent one the most fascinating implications of Einstein's theory of gravity, neutron stars in binary system are arguably its richest laboratory, where gravity blends with astrophysics and particle physics. I will discuss the rapid recent progress made in modelling these systems and show how the gravitational signal can provide tight constraints on the equation of state for matter at nuclear densities, as well as on one of the most important consequences of general relativity for compact stars: the existence of a maximum mass. Finally, I will discuss how the merger may lead to a phase transition from hadronic to quark matter. Such a process would lead to a signature in the post-merger gravitational-wave signal and open an observational window on the production of quark matter in the present Universe.
16:15 Uhr s.t., HS KPH

12.07.22Elena Aprile, University of Columbia
The XENON Dark Matter Project aims at the direct detection of Dark Matter WIMPs as they scatter off a liquid xenon target in a two-phase time projection chamber (TPC). With steadily increased target mass and lower background, the XENON experiments have set world-leading limits on a variety of WIMP interactions and over a broad mass range. I will present results from the first science data obtained with the new XENONnT experiment, which continues taking data at the Gran Sasso Underground Laboratory.
16:15 Uhr s.t., HS KPH

19.07.22Prof. Andreas Schäfer, University of Regensburg
The EIC project ist rapidly approaching CD-2 stage (Critical Decision 2; approval of preliminary design, cost, and schedule) and a large fraction of the international hadron physics community is focusing on the opportunities the EIC will provide and the challenges it will pose for theory. Precision and scope of the EIC experiments will be unprecedented and matching both is a highly non-trivial task. As illustrations I will review some aspects of this multifaceted topic without any claim to completeness.
16:15 Uhr s.t., HS KPH


Prof. Dr. Sebastian Böser
Institut für Physik, ETAP

Prof. Dr. Frank Maas
Institut für Kernphysik