Semesterübersicht Sommersemester 2024
Wintersemester 2023/2024  Sommersemester 2024  Wintersemester 2024/2025
Physikalisches Kolloquium
Institut für Physik 16:15 Uhr s.t., HS KPH 
Prof. Dr. Ulrich Stroth, Max Planck Institute for Plasma Physics, Garching  
In times of a shift towards a low CO2 energy supply and boosted by the recent success of laser fusion, the advantages of nuclear fusion in general have come into the focus of politics and private investors as an attractive energy source. This talk introduces the concept of magnetic fusion and outlines the path to a fusion reactor. The perspectives of magnetic fusion will be compared with those of laser fusion and the concepts of startups. The role of plasmas, in which energy is obtained from the fusion of hydrogen isotopes, and their physical properties are explained. Slides here...  

TheoriePalaver
Institut für Physik 14:00 Uhr s.t., Lorentz room (Staudingerweg 7, 5th floor) 
Julio Virrueta, Jena U.  
I will discuss the realtime dynamics of metric perturbations around the AdS black hole and argue that the dynamic of these modes is captured by a set of designer scalars in the background geometry. Using these results I will obtain the realtime Gaussian effective action, which includes both the retarded response and the associated stochastic fluctuations. Finally, I will discuss extensions beyond linear response.  

PRISMA+ Colloquium
Institut für Physik 13:00 Uhr s.t., LorentzRaum, 05127, Staudingerweg 7 
Prof. Dr. Koichi Hamaguchi, Univ./IPMU Tokyo, Japan  
SupernovaScope for the Direct Search of Supernova Axions  

Seminar über Theorie der kondensierten Materie / TRR146 Seminar
F. Schmid / G. Settanni / P. Virnau / L. Stelzl 14:30 Uhr s.t., MinkowskiRaum, 05119, Staudingerweg 7 
Felix Höfling, Freie Universität Berlin  
Emergent phenomena in flowing matter  

Seminar über Quanten, Atom und Neutronenphysik (QUANTUM)
Institut für Physik 14 Uhr c.t., IPH Lorentzraum 05127 
Dr. Felix Tennie, Imperial College, London, UK  
Nonlinear differential equations are ubiquitous in Physics, Engineering, Chemistry, Materials Science, and various other subjects. Numerical integration often requires resources exceeding current classical supercomputers. Quantum computing presents a fundamentally different computing paradigm. Quantum algorithms have a proven scaling advantage in many linear tasks such as Fourier transformation, matrix inversion, SVD, to name but a few. Yet, due to the linear evolution of quantum systems, integrating nonlinear dynamics on quantum computers is hard. In this talk I will present different approaches for integrating nonlinear differential equations on quantum computers, and will discuss their suitability for different types of quantum hardware.  

Seminar about Experimental Particle and Astroparticle Physics (ETAP)
Institut für Physik 12:30 Uhr s.t., Staudingerweg 7, Minkowskiraum 
Annika Stein, Institut für Physik  
Novel Jet Flavour Tagging Algorithms exploiting Adversarial Deep Learning Techniques  
at https://indico.him.unimainz.de/event/199/  

RHIND seminar on Mathematical Physics and String Theory
U. Mainz, LMU Munich, U. Heidelberg, U. Vienna 16:00 Uhr s.t. 
Giovanni Felder, ETHZürich  
Towards a mathematical description of superstring perturbation theory  
at Zoom, BigBlueButton  

TheoriePalaver
Institut für Physik 14:00 Uhr s.t., Lorentz room (Staudingerweg 7, 5th floor) 
Yann Gouttenoire, Tel Aviv U.  
Cosmological firstorder phase transitions are said to be strongly supercooled when the nucleation temperature is much smaller than the critical temperature. The phase transition takes place slowly and the probability distribution of bubble nucleation times is maximally spread. Hubble patches which get percolated later than the average are hotter than the background after reheating and potentially collapse into primordial black holes (PBHs). I will give a review of this PBHs formation mechanism and of its most recent developments.  

PRISMA+ Colloquium
Institut für Physik 13:00 Uhr s.t., LorentzRaum, 05127, Staudingerweg 7 
Prof. Dr. Bastian Märkisch, TU München  
Neutron Beta Decay with Perkeo III and Perc  

Seminar über Quanten, Atom und Neutronenphysik (QUANTUM)
Institut für Physik 14 Uhr c.t., IPH Lorentzraum 05127 
Prof. Dr. Ralf Röhlsberger, DESY, Hamburg  
Using the highintensity radiation of the European Xray FreeElectron Laser, we recently succeeded to excite the sharpest atomic transition in the hard Xray range, the 12.4 keV nuclear resonance of the stable isotope Scandium45 [1].
With its extremely narrow natural linewidth of 1.4 femtoeV, it opens not only new possibilities for the development of a nuclear clock, but also for research linked to the foundations of physics, such as time variations of the fundamental constants, the search for dark matter as well as probing the foundations of relativity theory.
Furthermore, our experiment demonstrates the great potential of selfseeding Xray lasers with high pulse rates as a promising platform for the spectroscopy of extremely narrowband nuclear resonances.
The next steps towards a nuclear clock based on Scandium45 require a further increase of the spectral photon flux using improved Xray laser sources at 12.4 keV and the development of frequency combs reaching up to this energy.
[1] Yuri Shvyd’ko et al., Nature 622, 471 (2023)  

Seminar über die Physik der kondensierten Materie (SFB/TRR173 Spin+X und SFB/TR288 Kolloquium, TopDynSeminar)
JGU 12:00 Uhr s.t., Media Room 
Kilian Leutner and Thomas Winkler, JGU Mainz  
This Friday, the 26th, from 12 to 2 pm, Kilian Leutner and Thomas Winkler will give a test run of the "Intermag 2024 Handson session: AI in magnetism."
We will give an introductory talk (~30 minutes) about AI in magnetism and more concrete information about our recent project: "AIaccelerated detection of spin structures in Kerrmicroscopy data."
Afterward, we will ask you to open your laptops and participate actively in the AI revolution. We will guide you through our repository. The goal is that participants can infer data and even train models on their own at the end of the session.
If you are interested, feel free to have a look at our paper and official repository:
Paper: LabrieBoulay et al., Phys. Rev. Appl. 21, 014014 (2024): https://doi.org/10.1103/PhysRevApplied.21.014014
Repository (v2.0): Winkler et al., Zenodo repository: https://doi.org/10.5281/zenodo.10997175
If you would like to join, please send an email to Kilian Leutner ( kileutne@students.unimainz.de ) by Thursday. Kilian Leutner will eventually send around links for a smaller data repository, install instructions this week for the session.
You can participate in this session at the Physics building in Mainz in the “Medienraum” (03431), or you can access the session via Teams using the following link: https://teams.microsoft.com/l/meetupjoin/19%3ameeting_MTRhNjI4ZWYtNDkyMC00YzQ1LWIyNzgtMzkxNjAzYjNjYjY2%40thread.v2/0?context=%7b%22Tid%22%3a%2251aa2b30c9fa40dbb91a3a53a8a08d85%22%2c%22Oid%22%3a%22e50b859d212d4ce0b8ca82e26bd02e43%22%7d .
(As this is a test talk, we are also happy about some feedback)  

Seminar über die Physik der kondensierten Materie (SFB/TRR173 Spin+X und SFB/TR288 Kolloquium, TopDynSeminar)
JGU 12:00 Uhr s.t., Media Room 
Kilian Leutner and Thomas Winkler, JGU Mainz  
This Friday, the 26th, from 12 to 2 pm, Kilian Leutner and Thomas Winkler will give a test run of the "Intermag 2024 Handson session: AI in magnetism."
We will give an introductory talk (~30 minutes) about AI in magnetism and more concrete information about our recent project: "AIaccelerated detection of spin structures in Kerrmicroscopy data."
Afterward, we will ask you to open your laptops and participate actively in the AI revolution. We will guide you through our repository. The goal is that participants can infer data and even train models on their own at the end of the session.
If you are interested, feel free to have a look at our paper and official repository:
Paper: LabrieBoulay et al., Phys. Rev. Appl. 21, 014014 (2024): https://doi.org/10.1103/PhysRevApplied.21.014014
Repository (v2.0): Winkler et al., Zenodo repository: https://doi.org/10.5281/zenodo.10997175
If you would like to join, please send an email to Kilian Leutner ( kileutne@students.unimainz.de ) by Thursday. Kilian Leutner will eventually send around links for a smaller data repository, install instructions this week for the session.
You can participate in this session at the Physics building in Mainz in the “Medienraum” (03431), or you can access the session via Teams using the following link: https://teams.microsoft.com/l/meetupjoin/19%3ameeting_MTRhNjI4ZWYtNDkyMC00YzQ1LWIyNzgtMzkxNjAzYjNjYjY2%40thread.v2/0?context=%7b%22Tid%22%3a%2251aa2b30c9fa40dbb91a3a53a8a08d85%22%2c%22Oid%22%3a%22e50b859d212d4ce0b8ca82e26bd02e43%22%7d .
(As this is a test talk, we are also happy about some feedback)  

Seminar about Experimental Particle and Astroparticle Physics (ETAP)
Institut für Physik 12:30 Uhr s.t., Staudingerweg 7, Minkowskiraum 
Jan Weldert, Pennsylvania State University  
Atmospheric neutrino oscillations with the IceCube Upgrade  
at https://indico.him.unimainz.de/event/199/  

Physikalisches Kolloquium
Institut für Physik 16:15 Uhr s.t., HS KPH 
Prof. Dr. Joacim Rocklöv, Heidelberg University  
In this talk I will introduce infectious diseases and their sensitivity to climate variability and change. I will describe and contrast experimental evidence with empirical observations and data. In the talk I will discuss systems and interactions enabling introduction and transmission of emergent vectors, hosts, and pathogens. I will further give examples of how mathematical processbased models and machine learning approaches are used and how they can be applied to study patterns and responses to these changes. Finally, I will talk about novel applications of machine learning in surveillance and early warnings, as well as the evaluation of interventions to guide effective responses. Slides here...  

TheoriePalaver
Institut für Physik 14:00 Uhr s.t., Lorentz room (Staudingerweg 7, 5th floor) 
Marco Fedele, IFIC, Valencia  
In the last decade, several measurements have been hinting at the possibility of Beyond Standard Model physics in B decays. Some of these observables have stayed “anomalous” after several experiments released multiple measurements of such quantities, while others have recently suffered a different fate. In this seminar I will recap the current status of experimental anomalies, critically reviewing the theoretical description of these observables in the Standard Model. I will therefore identify which are the quantities with the highest probability of being affected by New Physics, and which are the ones that on the other hand do not require an extension of the SM any longer.  

Seminar über Quanten, Atom und Neutronenphysik (QUANTUM)
Institut für Physik 14:00 Uhr s.t., IPH Lorentzraum 05127 
Prof. Dr. Matthias Christandl, University of Copenhagen, Denmark  
In these days, we are witnessing amazing progress in both the variety and quality of platforms for quantum computation and quantum communication. Since algorithms and communication protocols designed for traditional 'classical' hardware do not employ the superposition principle and thus provide no gain even when used on quantum hardware, we are in need of developing specific quantum algorithms and quantum communication protocols that make clever use of the superposition principle and extract a quantum advantage. "Quantum hardware needs quantum software", so to say. Furthermore, due to noise in the qubits, known as decoherence, an additional quantumspecific software layer is required that emulates a perfect quantum machine on top of a noise one. I will demonstrate our recent work on this subject with theorems as well data from university and commercial quantum devices.  

Physikalisches Kolloquium
Institut für Physik 16:15 Uhr s.t., HS KPH 
Prof. Dr. Michael Kramer, Max Planck Institute for Radio Astronomy, Bonn  
Pulsars, the natural beacons of the universe, put physics to extreme test. As neutron stars, they are not only the densest objects in the observable universe, but they also serve as highprecision laboratories for testing the general theory of relativity. Pulsars not only allow the observation of predicted effects that cannot be observed by other methods, but they provide also extremely precise tests of the properties of gravitational waves. The latest results even use pulsars as galactic gravitational wave detectors, which detect a continuous "hum" of spacetime. This buzz is, most likely, caused by the merging of supermassive black holes in the early universe. The talk gives an overview of the latest results and an outlook into the future. Slides here...  

TheoriePalaver
Institut für Physik 14:00 Uhr s.t., Lorentz room (Staudingerweg 7, 5th floor) 
Antonela Matijašić, MPP, Munich  
The stateoftheart in current twoloop QCD amplitude calculations is at fiveparticle scattering. In contrast, very little is known at present about twoloop sixparticle scattering processes. In recent years, the results for oneloop hexagon integrals to higher order in the dimensional regulator become available as well as the results on the maximal cut of the planar twoloop sixpoint integral families. In this talk, I will show the progress made in computing planar twoloop sixparticle Feynman integrals beyond the maximal cut using the differential equations method. In particular, I will discuss the canonical basis for several integral families in four spacetime dimensions and their function space.  

PRISMA+ Colloquium
Institut für Physik 13:00 Uhr s.t., LorentzRaum, 05127, Staudingerweg 7 
Prof. Dr. Gregor Kasieczka, Universität Hamburg  
Modern machine learning and artificial intelligence are starting to fundamentally change how we analyse huge volumes of data in particle physics and adjacent scientific disciplines. These breakthroughs promise new insights into major scientific questions such as the nature of dark matter or the existence of physical phenomena beyond the standard model.
This colloquium will provide an overview of recent, exciting developments with a focus on model agnostic discovery strategies — including first experimental results, fast simulations, and foundation models that simultaneously solve multiple tasks across multiple data sets.
Slides:
https://drive.google.com/file/d/1PR2orzmtn63oeV3IUxe1xLrnWulskcz/view?usp=sharing  

RHIND seminar on Mathematical Physics and String Theory
U. Mainz, LMU Munich, U. Heidelberg, U. Vienna 16:00 Uhr s.t. 
Alessandro Tanzini, SISSA Triest  
Painlevé/gauge theory correspondence and topological strings  
at Zoom, BigBlueButton  

Physikalisches Kolloquium
Institut für Physik 16:15 Uhr s.t., HS KPH 
Prof. Dr. Jochem Marotzke, Max Planck Institute for Meteorology, Hamburg  
I will first illustrate two key conclusions from the latest report of the Intergovernmental Panel on Climate Change, IPCC, from 2021. The first states that “it is unequivocal that human influence has warmed the atmosphere, ocean and land”. The second states that “global warming of 1.5°C and 2°C will be exceeded during the 21st century unless deep reductions in CO2 and other greenhouse gas emissions occur in the coming decades.” I will then explain how these results built on the work of Klaus Hasselmann and Syukuro Manabe, respectively, who shared the Nobel Prize in physics in 2021. The second of the statements was made possible through remarkable research progress during the past decade, and I will demonstrate how the scientific process within the IPCC turned a seeming scientific crisis into substantial progress. Finally, I will look at the still unsolved problem of understanding the future of the Atlantic Ocean circulation and how we tackle this problem in current research. Slides here...  

TheoriePalaver
Institut für Physik 14:00 Uhr s.t., Lorentz room (Staudingerweg 7, 5th floor) 
João Penedo, INFN, Rome3  
In recent years, modular invariance has been applied to the SM flavour puzzle, yielding compelling results. In this stringinspired paradigm, one does not require a multitude of scalar fields (flavons) with aligned VEVs and complicated potentials. Taking a bottomup approach, one may instead rely on a single complex field  the modulus. Yukawa couplings and mass matrices are obtained from functions of its VEV, which can be the only source of flavour symmetry breaking and of CP violation. Such predictive modular setups may, among other things, shed light on the patterns of fermion mixing, the origin of fermion mass hierarchies and the strong CP problem.  

PRISMA+ Colloquium
Institut für Physik 13:00 Uhr s.t., LorentzRaum, 05127, Staudingerweg 7 
Prof. Dr. John Bulava, Universität Bochum  
Although experimentally wellestablished, the nature of the Lambda(1405) hyperon resonance has long been a mystery. Constituent quark models have difficulty accommodating its low mass, while approaches based on chiral effective theory typically predict an additional state, the Lambda(1380), which is broad and difficult to identify. I will present the first lattice QCD computation of the coupledchannel $\pi\Sigma\bar{K}N$ scattering amplitude in the Lambda(1405) channel, which employs quark masses so that the $\pi\Sigma$ threshold is approximately 1380 MeV. This enables the unambiguous identification of the Lambda(1380) in addition to the Lambda(1405), thus supporting the exotic mesonbaryon `molecule' interpretation. Slides here...  

Seminar über Theorie der kondensierten Materie / TRR146 Seminar
F. Schmid / G. Settanni / P. Virnau / L. Stelzl 14:30 Uhr s.t., MinkowskiRaum, 05119, Staudingerweg 7 
Sonya Hansen, Flatiron Institute  
TBA  

Seminar über Quanten, Atom und Neutronenphysik (QUANTUM)
Institut für Physik 14:00 Uhr s.t., IPH Lorentzraum 05127 
Prof. Kenneth R. Brown, Duke University, USA  
Conical intersections often control the reaction products of photochemical processes and occur when two electronic potential energy surfaces intersect. Theory predicts that the conical intersection will result in a geometric phase for a wavepacket on the ground potential energy surface, and although conical intersections have been observed experimentally, the geometric phase has not been directly observed in a molecular system. Here we use a trapped atomic ion system to perform a quantum simulation of a conical intersection. The ion’s internal state serves as the electronic state, and the motion of the atomic nuclei is encoded into the motion of the ions. The simulated electronic potential is constructed by applying statedependent optical forces to the ion. We experimentally observe a clear manifestation of the geometric phase using adiabatic state preparation followed by motional state measurement. Our experiment shows the advantage of combining spin and motion degrees for quantum simulation of chemical reactions. We conclude with a discussion of future simulation directions.  

Physikalisches Kolloquium
Institut für Physik 16:15 Uhr s.t., HS KPH 
Prof. Dr. Cristian Micheletti, SISSA, Trieste, Italy  
Sampling equilibrium ensembles of dense polymer mixtures is a paradigmatically hard problem in computational physics, even in latticebased models. For instance, using realspace Monte Carlo to sample polymer systems becomes impractical for increasing size, rigidity, and density of the chains. In response to these challenges, we introduce and apply a formalism to recast polymer sampling as a quadratic unconstrained binary optimization (QUBO) problem [1].
Thanks to this mapping, dense systems of stiff polymers on a lattice can be efficiently sampled with classical QUBO solvers, resulting in more favourable performance scaling compared to realspace Monte Carlo [2]. Tackling the same problems with the DWave quantum annealer leads to further performance improvements [2]. As an application, we discuss the use of the quantuminspired encoding on a hitherto untackled problem, namely the linking probability of equilibrated melts of ring polymers, for which we unveil counterintuitive topological effects.
References
[1] C.Micheletti, P. Hauke and P. Faccioli, "Polymer physics by quantum computing", Phys. Rev. Lett. 127, 080501 (2021)
[2] F. Slongo, P. Hauke, P. Faccioli and C. Micheletti "Quantuminspired encoding enhances stochastic sampling of soft matter systems", Sci. Adv. 9, art. no adi0204 (2023) Slides here...  

TheoriePalaver
Institut für Physik 14:00 Uhr s.t., Lorentz room (Staudingerweg 7, 5th floor) 
Guilherme Guedes, DESY  
In this talk, I will go over the role of small instantons (SI) in increasing the axion mass. These SI will also enhance the effect of CPviolating operators which shift the axion potential minimum by an amount proportional to the flavorful couplings of the theory. Since physical observables must be flavor basis independent, we construct a basis of determinantlike flavor invariants that arise in instanton calculations containing the effects of dimensionsix CPodd operators. This new basis provides a more reliable estimate of the shift of the minimum of the axion potential, which is severely constrained by neutron electric dipole moment experiments. We show explicitly how these quantities arise in the case of 4quark and semileptonic operators, and how they can be used to constrain the ratio of the scales of SI and CPviolation. More generally, the flavor invariants introduced, together with an instanton NDA, can be used to more accurately estimate small instanton effects in the axion potential arising from any effective operator. We will also discuss how other shiftbreaking effects can be enhanced in the presence of SI.  

PRISMA+ Colloquium
Institut für Physik 13:00 Uhr s.t., LorentzRaum, 05127, Staudingerweg 7 
Prof. Dr. Prateek Agrawal, Oxford, UK  
Beyond the Standard Model through the Axion Lens  

Seminar über Quanten, Atom und Neutronenphysik (QUANTUM)
Institut für Physik 14 Uhr c.t., IPH Lorentzraum 05127 
Dr. Hans Keßler, Universität Hamburg  
In driven nonlinear systems, various kinds of bifurcations can be observed on their route to chaos. From the evolution of Floquet multipliers one can extract information which serves as a precursor for phase transitions and dynamical instabilities. This method is applied in classical nonlinear physics, for example, to obtain early warning signals.
Utilising our impressive control over an atomcavity platform, we are able to prepare our system in various dynamical regimes and study the bifurcation experimentally in a quantum gas to obtain insights that could potentially be applied to more complex systems.
We prepare a BoseEinstein condensate inside the centre of a cavity and pumping it perpendicular to the cavity axis with a standing wave light field. Upon crossing a critical pump strength, we observe a pitchfork phase transition from a normal to a steady state selforganized phase [1]. Employing an open three level Dicke model, this transition can be understood as a transition between two fixpoints, indicating a pitchfork bifurcation. If the pump strength is increased further, the system undergoes a Hopf bifurcation. This causes limit cycles, which have time crystalline properties, to emerge [2]. In this regime, our model no longer shows fixpoints but stable attractive periodic orbits [3]. For strong pumping, we observe a second bifurcation, in our case a NeimarkSacker bifurcation. Its main characteristics is an oscillation with two incommensurate frequencies, this may indicate the formation of a continuous time quasicrystal [4]. Finally, in the regime of very strong pumping, we observe chaotic dynamics with many contributing frequencies.
References:
[1] J. Klinder, et al., PNAS 112, 11 (2015)
[2] P. Kongkhambut, et al., Science 307 (2022)
[3] J. Skulte, et al., arXiv:2401.05332 (2023)
[4] P. Kongkhambut, et al., manuscript in preparation  

GRK 2516 Soft Matter Seminar
Uni Mainz 14:30 Uhr s.t., Minkowski Room, 05119, Staudingerweg 7 
Anastasios Sourpis, JGU, Physics  
Electrochemistry is a discipline promising to advance material science towards more environmentally friendly and sustainable technologies for energy solutions. Electrochemical systems are usually composed of interacting complex molecules, making understanding collective effects limited for macroscopic experiments. Computer simulations offer a way to obtain insights in silico. In particular, molecular dynamics simulations, with detailed interatomic potentials, allow us to rationalize experimental results by exploring the dynamics of physical systems through virtual experiments. In the first part of this thesis, I systematically review molecular dynamics simulation methods providing the foundation for preparing our physical system in silico. I introduce the basic principles of an allatom molecular simulation within the framework of statistical physics and discuss in detail the treatment of electrostatic interactions and the importance of dielectric boundary conditions. In the second part of this thesis, I present our molecular dynamics study of a liquid system composed of water and acetonitrile molecules and their response to an external electric field. This mixture exhibits unique properties, including a distinctive electrical conductivity detection in the absence of an electrolyte in novel electrolysis flow cells. However, the underlying physical mechanism behind this phenomenon remains unknown. As a first step to understanding this mechanism, this work focuses on the bulk system structure and how a macroscopic external electric field influences its properties.  
at Zoom  

Physikalisches Kolloquium
Institut für Physik 16:15 Uhr s.t., HS KPH 
Prof. Dr. Ingo Rehberg, University of Bayreuth  
Spherical magnets are an invaluable but affordable physics toy! While vividly demonstrating chemical, physical and mathematical problems, they can also greatly inspire creativity: Questions concerning the favoured state of dipole cluster configurations lead – via an encounter with tipping points – to the invention of magnetic gears based on degenerate continua. Open source animations and patentfree hardware to play with shall garnish this triptychon. Slides here...  

TheoriePalaver
Institut für Physik 14:00 Uhr s.t., Lorentz room (Staudingerweg 7, 5th floor) 
Daniel Spitz, MPI Leipzig  
Finding interpretable order parameters for the detection of topological dynamics and critical phenomena can be a challenging endeavour in lattice field theories. Tailored to detect and quantify topological structures in noisy data, topological data analysis (TDA) allows for the construction of sensitive observables. In this talk I will discuss two research projects, which highlight the potential of TDA for lattice fieldtheoretical studies. The first utilizes TDA to investigate the role of topological defects in regimes governed by universal selfsimilar dynamics. More specifically, in simulations of the paradigmatic O(N) vector model, the dynamics of topological defects can be studied via Betti curves computed from local energy densities. Based on Monte Carlo simulations of SU(2) lattice gauge theory, the second project shows how TDA computed from chromoelectric and magnetic fields, topological densities and Polyakov loops can be used to uncover a multifaceted picture of the deconfinement phase transition.
This applicationoriented talk is based on joint work with Viktoria Noel, Jan Pawlowski and Julian Urban.  

PRISMA+ Colloquium
Institut für Physik 13:00 Uhr s.t., LorentzRaum, 05127, Staudingerweg 7 
Prof. Dr. Kathrin Valerius, KIT  
Unfortunately, this talk had to be canceled due to unforeseen circumstances.  

Seminar über die Physik der kondensierten Materie (SFB/TRR173 Spin+X und SFB/TR288 Kolloquium, TopDynSeminar)
JGU 12:30 Uhr s.t., Gernot Gräff Room 
X. R. Wang, 1The Hong Kong University of Science and Technology, China 2Chinese University of Hong Kong (Shenzhen), China  
In this talk, I will first discuss several progresses made in our group about fundamental properties of skyrmions in chiral magnetic films. These include 1) skyrmion sizes in isolated, in crystal, or in stripy forms; 2) skyrmion nucleation, formation, and potential barrier energies; 3) the roles of magnetic field in skyrmion crystal formation; 4) the stability and existing conditions of composite skyrmions such as target skyrmions and skyrmion bags/cluster; 5) topological equivalence of stripy phases and skyrmion crystals. Then I will discuss a new theory about widely observed unusual anisotropic magnetoresistance (UAMR) in bilayers which leads to the notion of the spinHall MR (SMR) in the famous SMR theory. The theory is based on the universal features in all bilayer heterostructure: resistivity tensor depends on magnetization and interfacial field. I will show that the angular dependencies of UAMR do not depend on the microscopic details, thus are universal. Experiments that can test this theory against the SMR theory are also proposed.
** This work is supported by the National Key Research and Development Program (No. 2020YFA0309600), the NSFC Grant (No. 11974296), and HK RGC Grants (No. 16300523, 16300522, and 16302321).  

Physikalisches Kolloquium
Institut für Physik 16:15 Uhr s.t., HS KPH 
Prof. Dr. Claudia Felser, Max Planck Institute for Chemical Physics of Solids, Dresden  
Topology, a wellestablished concept in mathematics, has nowadays become essential to describe condensed matter. At its core are chiral electron states on the bulk, surfaces and edges of the condensed matter systems, in which spin and momentum of the electrons are locked parallel or antiparallel to each other. Magnetic and nonmagnetic Weyl semimetals, for example, exhibit chiral bulk states that have enabled the realization of predictions from high energy and astrophysics involving the chiral quantum number, such as the chiral anomaly, the mixed axialgravitational anomaly and axions. The potential for connecting chirality as a quantum number to other chiral phenomena across different areas of science, including the asymmetry of matter and antimatter and the homochirality of life, brings topological materials to the fore. Slides here...  

PRISMA+ Colloquium
Institut für Physik 13:00 Uhr s.t., LorentzRaum, 05127, Staudingerweg 7 
Prof. Dr. Jacobo LópezPavón, Universidad de Valencia, Spain  
Recent Developments in Heavy Neutral Leptons  

Seminar über Quanten, Atom und Neutronenphysik (QUANTUM)
Institut für Physik 14:00 Uhr s.t., IPH Lorentzraum 05127 
Prof. Nicolò Defenu, ETH Zürich  
The concept of universality has shaped our understanding of manybody physics, but is mostly limited to homogenous systems. The seminar introduces a definition of universal scaling on a nonhomogeneous graph. The corresponding scaling theory is expected to depend only on a single parameter, the spectral dimension ds, which plays the role of the relevant parameter on complex geometries. We will then focus on a concrete example, the longrange diluted graph (LRDG), which allows to tune the value of the spectral dimension continuously. By means of extensive numerical simulations, we probe the scaling exponents of a simple instance of O(N) symmetric models on the LRDG showing quantitative agreement with the theoretical prediction of universal scaling in fractional dimensions.  

Physikalisches Kolloquium
Institut für Physik 16:15 Uhr s.t., HS KPH 
Dr. Karen Alim, TU München  
Propagating, storing and processing information is key to take smart decisions – for organisms as well as for autonomous devices. In search for the minimal units that allow for complex behaviour, the slime mould Physarum polycephalum stands out by solving complex optimization problems despite its simple makeup. Physarum’s body is an interlaced network of fluidfilled tubes lacking any nervous system, in fact being a single gigantic cell. Yet, Physarum finds the shortest path through a maze. We unravel that Physarum’s complex behaviour emerges from the physics of active flows shuffling through its tubular networks. Flows transport information, information that is stored in the architecture of the network. Thus, tubular adaptation drives processing of information into complex behaviour. Taking inspiration from the mechanisms in Physarum we outline how to embed complex behaviour in active microfluidic devices and how to program human vasculature. Slides here...  

TheoriePalaver
Institut für Physik 14:00 Uhr s.t., Lorentz room (Staudingerweg 7, 5th floor) 
Melissa van Beekveld, Nikhef  
Parton showers are essential tools for interpreting particlecollision data. To get the most out of available and upcoming data, it is important that these showers incorporate stateoftheart theoretical predictions. The PanScales project aims to design parton showers that achieve higher logarithmic accuracy than any of the standard tools used at present. This talk will discuss the construction of logarithmically accurate parton showers, including the recent achievement of nexttonexttoleadinglogarithmic accuracy for the wide class of e+e observables known as event shapes, and its impact on phenomenology.  

PRISMA+ Colloquium
Institut für Physik 13:00 Uhr s.t., LorentzRaum, 05127, Staudingerweg 7 
Prof. Dr. Jessica Turner, IPPP, Durham University, UK  
I will discuss how proton decay, combined with gravitational waves, can be used to test Grand Unified Theories (GUTs). In particular, proton decay searches by large multipurpose neutrino experiments such as DUNE, HyperKamiokande, and JUNO will either discover proton decay or further push the symmetrybreaking scale above 10^16 GeV. Another possible observational consequence of GUTs is the formation of a cosmic string network produced during the breaking of the GUT to the Standard Model gauge group, which can produce a stochastic background of gravitational waves. Several gravitational wave detectors will be sensitive to this over a wide frequency range. I will demonstrate the nontrivial complementarity between the observation of proton decay and gravitational waves produced from cosmic strings in determining SO(10) GUT breaking chains and their compatibility with leptogenesis as a means of producing the observed matterantimatter asymmetry. Additionally, I will extend this discussion to include supersymmetric GUTs, taking into account recent findings from Pulsar Timing Arrays that have detected gravitational waves in the nanoHertz frequency range. Slides here...  

Seminar über Theorie der kondensierten Materie / TRR146 Seminar
F. Schmid / G. Settanni / P. Virnau / L. Stelzl 15:30 Uhr s.t., LorentzRaum, 05119, Staudingerweg 7 
Apratim Chatterji, Prof  
Under high cylindrical confinement, segments of ring polymers with internal loops can be made to
get localized along the long axis of the cylinder. The emergent organization of the polymer
segments occurs because of the entropic repulsion between internal loops which mutually exclude
each other position along the long axis of the cylinder [Phys.Rev.E, 106, 054502 (2022)].
We used these localization properties of segments in such topologically modified beadspring
models of ring polymers to identify the underlying mechanism of the evolution of bacterial
chromosome organization as the cell goes through its life cycle [Soft Matter 18, 56155631 (2022)].
Here, we show how to modify ring polymer topology by creating internal loops of two different
sizes within the polymer, and thereby create an asymmetry in the two halves of the modified ring
polymer. This allows us to strategically manipulate and harness entropic interactions between
adjacent polymers confined in a cylinder, such that a polymer prefers to orient itself in a specific
way with respect to its neighbours. Thus, we can induce entropy driven effective interactions
reminiscent of Isingspin like interactions between adjacent topologically modified polymers. We
consider a completely flexible beadspring model of polymers with only excluded volume
interactions between the monomers.
We extend the work to investigate the entropic organization of topologically modified ring
polymers confined within a sphere. We observe that for a single topologically modified polymer
within a sphere, the monomers of the bigger loop are statistically probable to be found closer to the
periphery. However, the situation is reversed when we have multiple such topologically modified
polymers in a sphere. The monomers of the small loops are found closer to the walls of the sphere.
We can increase this effect by introducing a large number of small loops in each ring polymers.  

Seminar über Quanten, Atom und Neutronenphysik (QUANTUM)
Institut für Physik 14 Uhr c.t., IPH Lorentzraum 05127 
Prof. Eugene Polzik, University of Copenhagen, Denmark  
Studies of extreme cases within quantum mechanics have always been particularly attractive. How macroscopic can objects be and still demonstrate unique quantum features, such as entanglement? What are the real limits of measurement precision in quantum mechanics? I will review our experiments where macroscopic objects are driven deep into the quantum regime. Observation of a quantum trajectory of motion in a quantum reference frame with, in principle, unlimited accuracy will be presented. A concept of a reference frame with an effective negative mass required for such observation will be introduced. Generation of an entangled EinsteinPodolskyRosen state between distant mechanical and atomic oscillators and progress towards application of those ideas to gravitational wave detection will be reported. Finally, a recent demonstration of entanglement enhanced magnetic induction tomography for medical applications will be presented.  

RHIND seminar on Mathematical Physics and String Theory
U. Mainz, LMU Munich, U. Heidelberg, U. Vienna 16:00 Uhr s.t. 
John Baez, UC Riverside  
The Tenfold Way  
at Zoom, BigBlueButton  

Physikalisches Kolloquium
Institut für Physik 16:15 Uhr s.t., HS KPH 
Dr. Thomas Cocolios, KU Leuven, Belgium  
Nuclear medicine is currently experiencing some major changes and developments: Lu177 has become a standard radionuclide for patient care, in particular with Lutathera® and Pluvito®, two recently marketed drug for endocrine and prostate cancers, respectively. Those successes are but the tip of the iceberg of possibilities: with 3000 radionuclides synthesized in the laboratory, it seems unbelievable that only a handful are actually used in medical applications. This is mostly due to the absence of a supply pipeline to support research until their production is picked up by the industry. To break that paradigm, CERN has established the MEDICIS facility (MEDical Isotopes Collected from ISolde), where the techniques developed for the last 50 years on radioactive ion beams are now applied to produce medical radionuclides for research. The success of the development of noncarrieradded Sm153 has led it to first clinical trials in 2024. At the European level, this has triggered a new consortium, federated around MEDICIS but with a larger reach, as PRISMAP, the European medical radionuclide programme. Slides here...  

PRISMA+ Colloquium
Institut für Physik 13:00 Uhr s.t., LorentzRaum, 05127, Staudingerweg 7 
Dr. Joel Swallow, CERN, Switzerland  
The NA62 experiment at CERN is the worlds leading K+ laboratory, with the primary goal of studying the ultrarare decay K+ > pi+ nu nu. In the last few years several key upgrades have been implemented giving improved performance for our currently ongoing datataking campaign.
In this colloquium I will introduce the NA62 experiment and this golden decay mode, K+ > pi+ nu nu, and the latest news on the analysis status. NA62 has a broad physics programme and I will also present the latest results from across our research programme, including hotoffthepress rare and forbidden K+ decay searches. Slides here...  

Seminar über Quanten, Atom und Neutronenphysik (QUANTUM)
Institut für Physik 14 Uhr c.t., IPH Lorentzraum 05127 
Dr. Janis Nötzel, TUM, München  
In this talk, we address the question of how some theoretically predicted quantum advantages could be utilized in future system design. We start with an overview of various theoretical descriptions of quantum communication systems, focusing mainly on data transmission tasks involving topics such as Holevo capacity and entanglementassisted capacity of a quantum channel as well as the use of entanglement for coordination in multiple access scenarios. We give a brief overview of the state of the art of implementations before moving on to an applied perspective, where we start from the state of the art in today's network design and explore the potential role of the abovementioned quantum system descriptions for future networks.
We conclude the talk by formulating system design questions.  

RHIND seminar on Mathematical Physics and String Theory
U. Mainz, LMU Munich, U. Heidelberg, U. Vienna 16:00 Uhr s.t. 
Matthew Young, Utah State University  
Abelian gauged RozanskyWitten theory via quantum Lie superalgebras  
at Zoom, BigBlueButton  

Physikalisches Kolloquium
Institut für Physik 16:15 Uhr s.t., HS KPH 
Prof. Dr. Klaus Blaum, MaxPlanck Institute for Nuclear Physics, Heidelberg  
The four fundamental interactions and their symmetries, the fundamental constants as well as the properties of elementary particles like masses and moments, determine the basic structure of the universe and are the basis for our so well tested Standard Model (SM) of physics. Performing stringent tests on these interactions and symmetries in extreme conditions at lowest energies and with highest precision by comparing, e.g., the properties of particles and their counterpart, the antiparticles, will allow us to search for physics beyond the SM. Any improvement of these tests beyond their present limits requires novel experimental techniques.
An overview is given on recent mass and gfactor measurements with extreme precision on single or few cooled ions stored in Penning traps. Among others the most stringent test of boundstate quantum electrodynamics could be performed. Here, the development of a novel technique, based upon the coupling of two ions as an ion crystal, enabled the most precise determination of a gfactor difference to date. This difference, determined for the isotopes 20,22Ne9+ with a relative precision of 5 × 10−13, improved the precision for isotopic shifts of g factors by about two orders of magnitude. Our latest results on precision measurements with exotic ions in Penning traps will be presented. Slides here...  

TheoriePalaver
Institut für Physik 14:00 Uhr s.t., Lorentz room (Staudingerweg 7, 5th floor) 
Lisong Chen, KIT  
Future electronpositron colliders, such as the CEPC, FCCee, and ILC, are poised to explore a new precision frontier, enabling an unprecedented level of scrutiny of the electroweak (EW) sector of the Standard Model (SM) and potentially uncovering new physics beyond the SM. Achieving this requires a deeper understanding of the SM through the calculation of radiative corrections to various welldefined observables, specifically the electroweak precision observables (EWPOs).
The first part of the talk provides a brief review of the EWPOs and the forefront of precision studies of these observables at future electronpositron colliders. In the second part, we introduce a novel modular framework for describing EW scattering and decay processes, including but not limited to Zresonance physics. This framework maintains gauge invariance while ensuring extensibility. It has been implemented in the publicly available objectoriented C++ library GRIFFIN, featuring full NNLO and leading higherorder contributions on the Zresonance, as well as NLO corrections off resonance. This framework is also capable of making predictions for new physics models relevant to these processes and can interface with Monte Carlo programs to account for real radiation.  

PRISMA+ Colloquium
Institut für Physik 13:00 Uhr s.t., LorentzRaum, 05127, Staudingerweg 7 
Dr. Alessandro Lovato, Argonne National Lab, USA  
Uncertainty Quantification in Nuclear Physics  

RHIND seminar on Mathematical Physics and String Theory
U. Mainz, LMU Munich, U. Heidelberg, U. Vienna 16:00 Uhr s.t. 
Yizhen Zhao, Weizmann  
Open 𝑟rspin and FJRW theory via the point insertion technique  
at Zoom, BigBlueButton  

Seminar über Quanten, Atom und Neutronenphysik (QUANTUM)
Institut für Physik 14 Uhr c.t., IPH Lorentzraum 05127 
Prof. Oded Zilberberg, Universität Konstanz  
Topological classification of matter has become crucial for understanding (meta)materials, with associated quantized bulk responses and robust topological boundary effects [1]. Topological phenomena have also recently garnered significant interest in nonlinear systems [2]. In particular, weak nonlinearities can result in parametric gain, leading to “nonHermitian” metamaterials and the associated topological classification of open systems [3]. Here, we venture into this expanding frontier using an approach that moves away from quasilinear approximations around the closed system classification. We harness instead the topology of structural stability of vector flows, and thus propose a new topological graph invariant to characterize nonlinear outofequilibrium dynamical systems via their equations of motion. We exemplify our approach on the ubiquitous model of a dissipative bosonic Kerr cavity, subject both to one and twophoton drives. Using our classification, we can identify the topological origin of phase transitions in the system, as well as explain the robustness of a multicritical point in the phase diagram. We, furthermore, identify that the invariant distinguishes population inversion transitions in the system in similitude to a Z2 index. Our approach is readily extendable to coupled nonlinear cavities by considering a tensorial graph index.
References
[1] T. Ozawa, H. M. Price, A. Amo, N. Goldman, M. Hafezi, L. Lu, M. Rechtsman, D. Schuster, J. Simon, O. Zilberberg, and I. Carusotto, Rev. Mod. Phys. 91, 015006 (2019).
[2] A. Szameit, and M. C. Rechtsman, Nat. Phys. (2024).
[3] K. Ding, C. Fang, and G. Ma, Nat. Rev. Phys. 4, 745 (2022).  

Seminar über die Physik der kondensierten Materie (SFB/TRR173 Spin+X und SFB/TR288 Kolloquium, TopDynSeminar)
JGU 14:00 Uhr s.t., 01 122 NewtonRaum 
Yaroslav Tserkovnyak, University of California, Los Angeles  
I will review our recent work that aims at harvesting quantum fluctuations of magnetic systems, with both quantum information and manybody physics in mind. Focusing on magnons as building blocks of collective spin dynamics in magnetic insulators, I will discuss the prospects of their scalable integration with proximal color centers, such as nitrogenvacancy impurities, using the latter as either quantum sensors, which can be operated in a range of different physical modalities, or qbits, whose entangled dynamics is governed by the common dissipative magnonic environment. Recent experiments on using color centers as spectrallyresolved sensors of magnetic dynamics demonstrate their strong coupling with a range of 2D materials. Inspired in part by the ideas from quantum optics, we are now pursuing the inverse functionality: imprinting collective noise of the tunable environment onto emergent manybody properties of colorcenter ensembles.  

Physikalisches Kolloquium
Institut für Physik 16:15 Uhr s.t., HS KPH 
Prof. Dr. Laura Kreidberg, Max Planck Institute for Astronomy, Heidelberg  
The recent launch of the James Webb Space Telescope (JWST) has revolutionized the field of exoplanet atmosphere characterization, thanks to its unprecedented sensitivity and broad wavelength coverage. In this talk, I will give a tour of the latest JWST results for transiting exoplanets, from gas giants down to rocky worlds. For the largest planets, I'll focus on the complex physical processes recently revealed in their atmospheres, including photochemistry, 3D effects, and cloud formation. Pushing down to smaller worlds, I'll share the first measurements of chemical composition for the elusive subNeptune population; and finally give an update on which (if any) rocky planets have atmospheres at all. Slides here...  

TheoriePalaver
Institut für Physik 14:00 Uhr s.t., Lorentz room (Staudingerweg 7, 5th floor) 
Jorinde van de Vis, Leiden U.  
In many extensions of the Standard Model, the universe underwent one or several first order phase transitions. Such phase transitions proceed via the formation and collision of bubbles. The bubble collisions can source a stochastic gravitational wave background signal. In the case of the electroweak phase transition, the characteristic frequency would fall right in the sensitivity band of LISA. We can thus use data from gravitational wave experiments to probe physics beyond the standard model. In this talk, I will discuss the contribution to the gravitational wave signal from sound waves, which is often the dominant contribution.
Predictions of the gravitational wave spectrum typically rely on hydrodynamic lattice simulations of the scalarplasma system. Hydrodynamic solutions of a single expanding bubble provide a bridge between the particle physics model and the hydrodynamic lattice simulation and encode much of the underlying particle physics information. Two relevant quantities in this computation are the bubble expansion velocity and the kinetic energy budget. I will discuss the computation of both quantities and present two approximation schemes for computing the wall velocity: the scenario of local thermal equilibrium and of a large enthalpy jump between the two phases.  

PRISMA+ Colloquium
Institut für Physik 13:00 Uhr s.t., LorentzRaum, 05127, Staudingerweg 7 
PD Dr. Teresa Marrodan, MPI Heidelberg  
The nature of dark matter is one of the most important open questions in modern physics. Astronomical and cosmological measurements provide strong evidence for its existence. Despite the many hypothetical candidate particles that have been proposed, experimental efforts have so far yielded only null results. Direct detection is a promising method for determining the nature of this dark component of the Universe. It allows, for example, to probe the existence of WIMPs (Weakly Interacting Massive Particles) via their elastic scattering off target nuclei down to tiny interaction cross sections. Several experimental strategies have been developed to measure the small recoil induced by dark matter interactions, with liquid xenon TPCs being one of the most successful.
This talk will discuss the status and main results of XENONnT and outline future plans with the DARWIN/XLZD observatory. Slides here...  

RHIND seminar on Mathematical Physics and String Theory
U. Mainz, LMU Munich, U. Heidelberg, U. Vienna 16:00 Uhr s.t. 
Catherine Meusburger, University of Erlangen  
DijkgraafWitten TQFT with defects  
at Zoom, BigBlueButton  

Physikalisches Kolloquium
Institut für Physik 16:15 Uhr s.t., HS KPH 
 canceled  Dr. Kerem Çamsarı, University of California, Santa Barbara  
tba  

TheoriePalaver
Institut für Physik 14:00 Uhr s.t., Lorentz room (Staudingerweg 7, 5th floor) 
Peter Reimitz, Sao Paulo U.  
Highluminosity colliders and fixedtarget facilities using proton beams are sensitive to new weakly coupled degrees of freedom across a broad mass range. In this talk, we will discuss various production modes for dark vector particles in proton beam experiments. First, we will set the stage by reviewing light physics models, including new vector particles, discuss how these models could solve the shortcomings of the SM, and present some current and future search strategies. After briefly discussing dark photon production in meson decays and DrellYan, we will have a closer look at dark bremsstrahlung. Dark bremsstrahlung is particularly important for dark vectors with masses between 0.51.5 GeV due to resonant mixing with hadronic resonances. This production mode will be crucial for sensitivity predictions for future experiments like SHiP and proposals like the Forward Physics Facility. We revisit the calculation of dark photons via initial state radiation in nonsingle diffractive scattering, using an improved approach to the splitting function and the timelike electromagnetic form factor.  

PRISMA+ Colloquium
Institut für Physik 13:00 Uhr s.t., LorentzRaum, 05127, Staudingerweg 7 
Prof. Dr. Louis Strigari, Texas University, USA  
Astrophysical and Terrestrial Applications of Coherent Neutrino Scattering  

Seminar über Quanten, Atom und Neutronenphysik (QUANTUM)
Institut für Physik 14 Uhr c.t., IPH Lorentzraum 05127 
Prof. Nir BarGill, Hebrew University, Jerusalem  
The study of open quantum systems, quantum thermodynamics and quantum manybody spin physics in realistic solidstate platforms, has been a longstanding goal in quantum and condensedmatter physics. In this talk I will address these topics through the platform of nitrogenvacancy (NV) spins in diamond, in the context of bath characterization, purification (or cooling) of a spin bath as a quantum resource and for enhanced metrology and sensing.
I will first describe our work on characterizing noise using robust techniques for quantum control ([1], in collaboration with Ra’am Uzdin). This approach suppresses sensitivity to coherent errors while enabling noise characterization, providing a useful tool for the study of complicated open quantum systems, with the potential for contributions to enhanced sensing. I will then present a general theoretical framework we developed for Hamiltonian engineering in an interacting spin system [2]. This framework is applied to the coupling of the spin ensemble to a spin bath, including both coherent and dissipative dynamics [3]. Using these tools I will present a scheme for efficient purification of the spin bath, surpassing the current stateoftheart and providing a path toward applications in quantum technologies, such as enhanced MRI sensing.
Finally, if time permits, I will describe our work in using NVbased magnetic microscopy to implement quantum sensing in various modalities. I will present advanced techniques for improving sensing bandwidth using compressed sensing and machine learning. Demonstrations of NV sensing capabilities will include measurements of 2D vdW magnetic materials, and specifically the phase transition of FGT through local imaging of magnetic domains in flakes of varying thicknesses [4], as well as a technique for sensing radical concentrations through the change in the charge state of shallow NVs ([5], in collaboration
with Uri Banin).
1. P. PENSHIN ET. AL., SUBMITTED.
2. K. I. O. BEN’ATTAR, D. FARFURNIK AND N. BARGILL, PHYS. REV. RESEARCH 2, 013061 (2020).
3. K. I. O. BEN’ATTAR ET. AL., IN PREPARATION.
4. G. HAIM ET. AL., IN PREPARATION.
5. Y. NINIO ET. AL., ACS PHOTONICS 8, 7, 19171921 (2021).  

Seminar über Theorie der kondensierten Materie / TRR146 Seminar
F. Schmid / G. Settanni / P. Virnau / L. Stelzl 16:15 Uhr s.t., MinkowskiRaum, 05119, Staudingerweg 7 
Lisa Hartung, Prof  
Interacting particle systems and partial differential equations  

Seminar über die Physik der kondensierten Materie (SFB/TRR173 Spin+X und SFB/TR288 Kolloquium, TopDynSeminar)
JGU 14:00 Uhr s.t., 01 122 NewtonRaum 
Satoru Emori, Department of Physics, Virginia Polytechnic Institute and State University, U.S.A.  
Energyefficient spintronic devices require a large spinorbit torque (SOT) and low damping to excite magnetic precession. In conventional devices based on heavymetal/ferromagnet bilayers, reducing the ferromagnet thickness to ~1 nm enhances the torque – but dramatically increases the damping.
I will present my team’s new approach toward attaining low damping and a sizable SOT in singlelayer, 10nmthick FeNi alloys. A vertical Fe:Ni compositional gradient is designed to provide the necessary asymmetry for SOT generation. We confirm low effective damping in FeNi even with a steep compositional gradient. More remarkably, we reveal a sizable antidamping SOT even without any intentional compositional gradient. Through noninvasive depthprofile measurements, we identify a lattice strain gradient as the key asymmetry giving rise to the SOT. Our findings provide fresh insights into damping and SOTs in singlelayer ferromagnets for powerefficient spintronic devices.  

RHIND seminar on Mathematical Physics and String Theory
U. Mainz, LMU Munich, U. Heidelberg, U. Vienna 16:00 Uhr s.t. 
Emanuel Scheidegger, Peking University  
TBA  
at Zoom, BigBlueButton  

Physikalisches Kolloquium
Institut für Physik 16:15 Uhr s.t., HS KPH 
Prof. Dr. Frank Saueressig, Radboud University, NL  
Fusing the principles of general relativity and quantum mechanics in a consistent theoretical framework still constitutes one of the main open challenges in theoretical physics today. Over the last decades, the gravitational asymptotic safety program has taken significant steps towards achieving this goal. A central virtue, driving the success of the approach, is its conservative nature: the program builds on wellestablished principles of quantum field theory and extends them in a rather minimalistic way. In this talk, we will review the key developments in the program, building up to its present status. I will also attempt to give an outlook on the challenges that need to still be addressed in the future. Slides here...  

Physikalisches Kolloquium
Institut für Physik 16:15 Uhr s.t., HS KPH 
Prof. Dr. Reinhard Noack, Philipps University Marburg  
Correlated Electrons from Zero to Infinite Dimensions: Early Days of KOMET 7 in Mainz.
I will talk about the problems in correlated electron systems that occupied us in the early days of the KOMET 7 research group headed by Peter van Dongen. These problems include quantum impurity problems as well as the dynamical mean field theory (DMFT), i.e., correlated electrons in the infinitedimensional limit. At first glance, these two problems are very different because the impurity problem is in a sense zerodimensional, whereas the DMFT is formally infinitedimensional. However, the effective problems and solution methods of these two problems are losely related, and both approaches can be used to describe the behavior of real threedimensional materials. In addition, a major activity of group members has been to develop and use matrixproductstate and tensornetwork methods, especially the density matrix renormalization group.
These methods are ideally suited to study quasionedimensional and twodimensional strongly correlated systems. They can be applied to a variety of
systems ranging from transitionmetal coumpounds such as the cuprates to organometallic materials such as Bechgaard salts as well as to quantum simulators formed from cold atomic gases on optical lattices. Slides here...  

TheoriePalaver
Institut für Physik 14:00 Uhr s.t., Lorentz room (Staudingerweg 7, 5th floor) 
Jordy de Vries, Amsterdam U., Nikhef  
The fact that neutrinos are massive particles can be neatly explained by the existence of (at least two) additional neutrinos, called sterile neutrinos. Depending on their mass, sterile neutrinos can be looked for in various experiments. I will discuss how sterile neutrinos can be probed indirectly in neutrinoless double beta decay experiments and how this search compares to more direct probes and how it can test lowscale leptogenesis as a solution for the baryon number asymmetry of the universe.  

PRISMA+ Colloquium
Institut für Physik 13:00 Uhr s.t., LorentzRaum, 05127, Staudingerweg 7 
Prof. Dr. Stefan Schoenert, TU Munich  
Since neutrinos have no electric charges, they may be their own antiparticles, referred to as Majorana neutrinos, and thus violate lepton number conservation. Neutrinoless double beta decay would be a direct consequence, and the search for this decay mode is the most sensitive method to unravel the Majorana nature of neutrinos. By operating bare germanium diodes, enriched in Ge76, in an active liquid argon shield, GERDA achieved an unprecedently low background index of 5.2∙10−4 counts/keV kg yr in the signal region and collected an exposure of 127 kg yr in a backgroundfree regime. No signal was observed, and a limit on the halflife of 0νββ decay in Ge76 is set at T1/2 > 1.8∙1026 yr (90 % C.L.) [1] and Majorana neutrino masses are constrained to mββ< 79–180meV (90\% C.L.). The LEGEND Collaboration builds on the success of GERDA and MJD, and develops a phased, Ge76based doublebeta decay experimental program with a T1/2  discovery potential beyond 1028 years. Its first stage, LEGEND200, started datataking in early 2023, and LEGEND1000 is under preparation. The first results from LEGEND200, based on 48.3 kg·yrs of data, were presented in June at the Neutrino 2024 conference in Milan and will be discussed.  

Seminar über die Physik der kondensierten Materie (SFB/TRR173 Spin+X und SFB/TR288 Kolloquium, TopDynSeminar)
JGU 16:00 Uhr s.t., 01 122 NewtonRaum 
Elisa De Ranieri, EditorinChief, Newton  
Ever wondered how influential journals select content for publication and how peer review works? In this talk, I will discuss the editorial process at these journals, which typically rely on professional editors, focusing in particular on the Cell Press portoflio and introducing Newton, our new flagship physics journal. I will also share my views on current trends in scientific publishing, and provide tips on how to maximise the fit of your manuscript for highimpact journals and on how to deliver an appropriate reviewer report if you are invited to review a manuscript.  

TheoriePalaver
Institut für Physik Sonderseminar: 14:00 Uhr s.t., Lorentz room (Staudingerweg 7, 5th floor) 
Andrew McLeod, Edinburgh U.  
While the mathematical structure of scattering amplitudes has long been known to be constrained by principles such as causality and locality, the explicit form of these constraints has remained difficult to work out in practice. In this talk, I present a new method that sidesteps many of these difficulties, which allows us to derive large classes of novel constraints on Feynman integrals. In particular, through the identification of what singularities can still be reached after localizing to certain minimal cuts, strong restrictions can be placed on the ordered pairs of discontinuities that are allowed to appear in Feynman integrals. These restrictions, which we refer to as genealogical constraints, can be worked out for integrals involving arbitrary configurations of massive and massless particles, and hold to all orders in dimensional regularization.  
Sonderseminar  

Seminar über die Physik der kondensierten Materie (SFB/TRR173 Spin+X und SFB/TR288 Kolloquium, TopDynSeminar)
JGU 14:00 Uhr s.t., 01 122 NewtonRaum 
Prof. Shixun Cao, Institute for Quantum Science and Technology Shanghai University  
This presentation is to introduce our published science paper (Science 361, 794–797 (2018)), which is a cooperation work of Shanghai University and Rice University, Osaka University, Japan Science and Technology Agency, Argonne National Laboratories, Peking University, Universität DuisburgEssen, and Max Planck Institute for Polymer Research. The main point of this work is as follows:
The interaction of N twolevel atoms with a singlemode light field is an extensively studied manybody problem in quantum optics, first analyzed by Dicke in the context of superradiance. A characteristic of such systems is the cooperative enhancement of the coupling strength by a factor of N1/2. In this study, we extended this cooperatively enhanced coupling to a solidstate system, demonstrating that it also occurs in a magnetic solid in the form of mattermatter interaction. Specifically, the exchange interaction of N paramagnetic erbium(III) (Er3+) spins with an iron(III) (Fe3+) magnon field in erbium orthoferrite (ErFeO3) exhibits a vacuum Rabi splitting whose magnitude is proportional to N1/2. Our results provide a route for understanding, controlling, and predicting novel phases of condensed matter using concepts and tools available in quantum optics.
And the Science journal introduces this work as: One of the earliest and most intensively studied problems in quantum optics is the interaction of a twolevel system (an atom) with a single photon. This simple system provides a rich platform for exploring exotic lightmatter interactions and the emergence of more complex phenomena such as superradiance, which is a cooperative effect that emerges when the density of atoms is increased and coupling between them is enhanced. Going beyond the lightmatter system, Li et al. observed analogous cooperative effects for coupled magnetic systems. The results suggest that ideas in quantum optics could be carried over and used to control and predict exotic phases in condensed matter systems.
email: sxcao@shu.edu.cn (S.C.)  

GRK 2516 Soft Matter Seminar
Uni Mainz 14:30 Uhr s.t., Minkowski Room, 05119, Staudingerweg 7 
Prof. Julian Thiele, University of Magdeburg  
(SFB 1552 Seminar Series)  
at Zoom  
