Institut für Theoretische Physik

15.04.2025

Theoretische Physik

Theoretisch-physikalisches Seminar - Dienstag

Andreas Läuchli

Thermalisation Dynamics of Isolated Quantum Many Body Systems

tba

Kontakt: Theoretische Physik

17.04.2025

Theoretische Physik

Seminar Statistical Physics

Kirill Polovnikov

A fractal polymer with quenched disorder of loops as a model of chromosome organization

Kontakt: Peter Sollich

24.04.2025

Theoretische Physik

Seminar Statistical Physics

Dima Makarov

tba

Kontakt: Peter Sollich

24.04.2025

Theoretische Physik

Theoretisch-physikalisches Seminar - Donnerstag

Christian Schilling

Entanglement in Identical Particle Systems:
Foundation and Applications

Entanglement is a fundamental feature of the quantum world and a key resource for quantum information processing. While the concept of entanglement for distinguishable particles is well established, its validity for identical particles remains a subject of debate and misconceptions. In this talk, we resolve this foundational issue: We demonstrate that identical particles do not form proper subsystems, rendering the concept of entanglement inapplicable to identical particles in first quantization. However, in second quantization, where the focus shifts from particles to the inherently distinguishable orbitals, entanglement becomes well-defined. We then systematically apply this perspective to physics and chemistry. In particular, we show how quantum phase transitions manifest within this framework and how it provides a deeper understanding of chemical bonding. Furthermore, we propose a systematic approach to enhancing wave function methods for strongly correlated electron systems, relevant to both classical and quantum computing. Altogether, these insights highlight the deep connection between quantum information and many-body physics, demonstrating fruitful synergies that can foster the second quantum revolution.

Kontakt: Theoretische Physik

24.04.2025

Theoretische Physik

Seminar Statistical Physics

Dmitrii Makarov

Random walks on rough, fluctuating energy landscapes

Kontakt: Peter Sollich

24.04.2025

Theoretische Physik

Quantenfeldtheorie

Kontakt: K.-H. Rehren

28.04.2025

Theoretische Physik

Quantenfeldtheorie (Forschungsseminar M.Phy.412)

David Cabo Almeida

Freeze-In at strongly couplings: a new parameter space for Dark Matter

Freeze-in is a well-established mechanism for the early-universe production of Dark Matter (DM). In the standard freeze-in scenario, a feeble coupling is required to reproduce the observed DM abundance. Moreover, it typically assumes zero or negligible initial DM abundance.In this talk, I will discuss how the mere existence of gravity can lead to non-negligible initial abundances. I will show how late-time reheating provides a natural solution to this issue. An advantage of this solution is that it leads to a regime of Boltzmann-suppressed production. This allows freeze-in to occur with stronger couplings, opening a new parameter space for well-studied models such as those with a Z' mediator. Within this framework, I will show how current and future direct detection experiments play a crucial role in constraining these models.

Kontakt: Steffen Schumann

29.04.2025

Theoretische Physik

Theoretisch-physikalisches Seminar - Dienstag

Andre Eckardt

Controlling many-body quantum systems using driving and dissipation

In recent years, we have seen major progress in the non-equilibrium control of many-body quantum systems. One tool, which has been applied successfully, is Floquet engineering, i.e. the use of strong time-periodic driving for effectively changing the properties of the system. A prominent example is the realization of effective magnetic fields for charge neutral particles (like atoms in optical lattices or photons in superconducting circuits). Another approach is known as reservoir engineering. Here the system is coupled to a controlled environment, which is designed to either cool the system or to stabilize a non-equilibrium steady state of interest. I will report on recent work, where we combine both approaches in open Floquet systems. One motivation is to use dissipation in order to counteract unwanted heating as it necessarily occurs in Floquet engineered systems, e.g. for the preparation of Floquet engineered topological states of matter. Another motivation is the stabilization of non-equilibrium steady states. Here, I will in discuss ordering away from equilibrium, like driving-induced Bose-condensation.

Kontakt: Theoretische Physik

07.05.2025

Theoretische Physik

Aktuelle Probleme der theoretischen Festkörperphysik (Forschungsseminar M.Phy.411)

Giovanna Morigi

canceled!

Efficient retrieval of information is a core operation in the world wide web, is essential for the sustainance of living organism, and is a paradigm for optimization algorithms. Inspired by the food search dynamics of living organisms, we discuss a search on a graph with multiple constraints where the dynamics is a selforganized process resulting from the interplay of coherent dynamics and Gaussian noise. We show that Gaussian noise can be beneficial to the search dynamics leading to significantly faster convergence to the optimal solution. We then analyse how these concepts can be extended to quantum searches, cast in terms of spatial searches on a graph and discuss whether and when the efficiency of noise-assisted quantum searches can outperform the one of unitary protocols.

Kontakt: Fabian Heidrich-Meisner

08.05.2025

Theoretische Physik

Seminar Statistical Physics

Gabriel Knotz

Mean back relaxation demonstrates broken detailed balance in cells

Kontakt: Peter Sollich

08.05.2025

Theoretische Physik

BornHilbertSeminar

Masud Chaichian

- canceled !!! -

Kontakt: L. Covi

08.05.2025

Theoretische Physik

Quantenfeldtheorie

Matyas Draskovits

Quarkonia production with the Sherpa event generator

Kontakt: Steffen Schumann

15.05.2025

Theoretische Physik

Seminar Statistical Physics

Kristian Blom

Hallmarks of deception in asset-exchange models

Kontakt: Peter Sollich

19.05.2025

Theoretische Physik

CMT

Viktor Eisler

tba

tba

Kontakt: Prof. Dr. Fabian Heidrich-Meisner

22.05.2025

Theoretische Physik

Seminar Statistical Physics

Daniele Gamba

Casimir Interactions between Moving Bodies

Kontakt: Peter Sollich

05.06.2025

Theoretische Physik

Seminar Statistical Physics

Felix Tippner

How topologically distinct non-equilibrium currents imprint on projected observables

Kontakt: Peter Sollich

12.06.2025

Theoretische Physik

Seminar Statistical Physics

Lars Stutzer

Stochastic Calculus for Markov Jump Processes and its Application to Temperature Perturbations

Kontakt: Peter Sollich

17.06.2025

Theoretische Physik

Theoretisch-physikalisches Seminar - Dienstag

Gerhard Gompper

Swimming and Swarming of Cognitible Self-Steering Active Particles

Active Brownian particles and aligning Vicsek particles are the most frequently employed models to describe the dynamics and collective behavior of motile active matter [1,2]. However, for living systems, activity and locomotion is combined with sensing of the environment and adaption of motion. We study such system by considering “intelligent” active particles with visual perception and self-steering in dry [3-6] and wet systems [7,8]. Our model of cognitive self-steering particles consists of intelligent active Brownian particles (iABPs), which are equipped with an orientational response to an instantaneous visual input of the positions of neighbors within a vision cone -- with limited maneuverability (ability to change the propulsion direction) [3-5]. The redirection of particle motion can be either to follow other particles, or to avoid them. This model can be employed to study the collective motion of many identical iAPBs [3,4], e.g. to describe the motion of pedestrians in confinement or at an intersection [5], but also the pursuit of a moving target by single predator [6]. In many systems, like flocks of birds and schools of fish, it is obvious that alignment of motion with neighbors is also important. The ratio of vision-related maneuverability and alignment-induced steering then controls swarm shapes and dynamics [4]. In wet systems, a combination of alignment interactions and hydrodynamic interactions plays an essential role [7,8], where particles are modelled as “intelligent” squirmer (iSquirmers). Here,pushers and pullers display very different emergent behaviors. References: [1] J. Elgeti, R.G. Winkler, G. Gompper, Rev. Prog. Phys. 78, 056601 (2015) [2] G. Gompper et al., J. Phys. Condens. Matter 37, 143501 (2025). [3] R.S. Negi, R.G. Winkler, G. Gompper, Soft Matter 18, 6167 (2022) [4] R.S. Negi, R.G. Winkler, G. Gompper, Phys. Rev. Research 6, 013118 (2024) [5] P. Iyer, R.S. Negi, A. Schadschneider, and G. Gompper, Commun. Phys. 7, 379 (2024) [6] S. Goh, R.G. Winkler, G. Gompper, New J. Phys. 24, 093039 (2022) [7] S. Goh, R.G. Winkler, G. Gompper, Commun. Phys. 6, 31 (2023) [8] S. Goh, E. Westphal, R.G. Winkler, G. Gompper, Phys. Rev. Research 7, 013142 (2025)

Kontakt: Theoretische Physik

24.06.2025

Theoretische Physik

Theoretisch-physikalisches Seminar - Dienstag

Jens Bardarson

The information lattice: characterizing many-body states and dynamics

I will review the information lattice and its use for characterizing many-body states and many-body dynamics. The information lattice provides a local decomposition of information (entanglement) into scales that allows us to characterize many-body states according to their distribution of information. Furthermore, under unitary time evolution the local information flows like a conserved fluid on the information lattice. In thermalizing systems the flow of information is from small scales to large scales. I will also discuss an approximate algorithm for time evolution that uses this fact to discard large scale inaccessible information in a way that conserves expectation values of local observables and allows us to reach large times for large system sizes, allowing the extraction of diffusion constants from the many-body dynamics.

Kontakt: Theoretische Physik

01.07.2025

Theoretische Physik

Theoretisch-physikalisches Seminar - Dienstag

Arnab Kundu

Driven CFTs, Dynamical Phase Transitions & Geometric Duals

Abstract: Driven quantum systems can lead to novel and interesting phases of matter. In this talk, we will summarize recent results on phase structures and phase transitions in the context of driven Conformal Field Theories in two dimensions and beyond. In particular, we will discuss how non-trivial (dynamical, non-equilibrium) phases emerge that can be classified according to the conjugacy classes of the corresponding sl(2,R) transformation. We will also explain how a geometric (more generally, Holographic) (quantum) gravitational dual description encodes the information of these phases and how the experience of a bulk observer is encoded in the CFT Hamiltonian. Finally, we will conclude with potential future directions.

Kontakt: Theoretische Physik

08.07.2025

Theoretische Physik

Theoretisch-physikalisches Seminar - Dienstag

Matthias Kaminski

Entanglement and thermalization in ultra-cold gas, quark-gluon plasma & black holes

When zooming in on the fabric of spacetime, quantum effects become important. Recent theoretical results strongly suggest that spacetime is a form of quantum entanglement. However, there are many open questions about how to reconstruct spacetime from quantum entanglement. In this seminar, we discuss possibilities to experimentally test the relation between spacetime and entanglement.

Kontakt: Theoretische Physik

10.07.2025

Theoretische Physik

Seminar Statistical Physics

Leila Henkes

Mean back relaxation for densities

Kontakt: Peter Sollich