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Colloquium

Topic:

Molecular-level ionizing-radiation matter interactions and their consequences

Date:

13.12.22

Time:

14:15

Place:

H6

Guest:

Prof. Dr. Arno Ehresmann

Universität Kassel

Abstract:

The interaction between ionizing electromagnetic radiation and dense matter and processes following an initial ionization event are fundamental to a variety of important challenges in society and science. If those processes would be fully understood, this could be the basis to develop measures to avoid or cure hazardous effects due to ionizing-radiation exposure of biologically relevant systems, to develop treatments for diseases occurring as consequences of such processes in living entities, or, in a completely different field of science, to understand fundamental processes in astrochemistry. In the presentation I will show how spectroscopy of dispersed fluorescence, electrons and by multi-coincidence methods upon ionization by monochromatized synchrotron and free-electron laser radiation can be used to clarify and quantify those fundamental processes. By increasing the complexity of the investigated systems stepwise from photoionization and photodissociation processes of individual atoms or molecules over processes occurring in clusters towards processes occurring in liquids my group tries to investigate how processes essentially known to us in individual molecules may be changed and which other processes may occur when those molecules are embedded in (approximately) realistic environments.

Contact person:

T. Kuschel

Colloquium Mathematical Physics

Topic:

tba

Date:

13.01.23

Time:

16:15

Place:

D5-153

Guest:

Felix Finster

Universität Regensburg

Abstract:

Contact person:

G. Akemann

Seminar High Energy Physics

Topic:

Relativistic dynamics in black hole systems and efforts toward the discovery of nano-Hz GWs

Date:

12.12.22

Time:

16:15

Place:

D6-135

Guest:

Prerna Rana

TIFR Mumbai

Abstract:

The study of bound particle trajectories around a rotating black hole is crucial to understanding many as- trophysical phenomena. I will present a new closed-form analytic solution for the generalized non-equatorial eccentric bound particle trajectories, and their fundamental frequencies, in the Kerr spacetime using general relativity. The trajectories are expressed in the eccentricity, inverse-latus rectum, spin, and Carter’s constant (e, ?, a, Q) parameter space. The generalized solutions also enabled us to obtain the necessary bound orbit conditions for (e, ?, a, Q) and novel specialized formulae for equatorial, spherical, and non-equatorial sepa- ratrix orbits. Next, I will present the Generalized Relativistic Precession Model (GRPM), which utilizes the analytic solutions of trajectories in the Kerr spacetime, to explain the origin of Quasi-periodic oscillations (QPOs) in black hole X-ray binaries (BHXRB). Our analysis of the plasma fluid flow around a Kerr black hole in the relativistic disk edge suggests that instabilities cause QPOs to originate in a torus region spanned by geodesics. The application of the GRPM will also be shown for X-ray QPOs seen in Seyferts galaxies. Toward the end, I will discuss our recent efforts for the first official data release of the Indian Pulsar Timing Array (InPTA), which will be incorporated into the global effort of the International Pulsar Timing Array (IPTA) consortium to discover nano-Hz gravitational waves emitted by the relativistic supermassive black hole binaries.

Contact person:

D. Schwarz

Seminar Condensed Matter

Topic:

Nonequilibrium non-Markovian steady states in open quantum many-body systems: Persistent oscillations in Heisenberg quantum spin chains

Date:

09.12.22

Time:

14:15

Place:

D5-153

Guest:

Regina Finsterhölzl

Universität Konstanz

Abstract:

We investigate the effect of a non-Markovian, structured reservoir on an open Heisenberg spin chain by applying coherent time-delayed feedback control to it. The structured reservoir couples frequency-dependent to the spin chain and therefore induces a memory, thus the spin chain interacts partially with its own past. We demonstrate that with this new paradigm of a non-Markovian temporal driving scheme, it is possible to generate persistent oscillations within the many-body system and thus induce highly non-trivial states which dynamically store excitation within the chain. These oscillations occur at special points in the stability landscape and persist for different chain lengths and different initial excitations within the chain. We propose a non-invasive partial characterization of the chain by exploiting the fact that the different trapping conditions which arise each relate to specific steady states within the chain.

Contact person:

FOR2692/Jürgen Schnack

Seminar Mathematical Physics

Topic:

tba

Date:

19.01.23

Time:

16:00

Place:

D5-153

Guest:

Tobias Hartung

University of Bath

Abstract:

Contact person:

Gernot Akemann

Seminar AG Zufallsmatrizen

Topic:

Extremal statistics of quadratic forms of GOE/GUE eigenvectors

Date:

14.12.22

Time:

09:00

Place:

ZOOM / Konferenzschaltung

Guest:

Ben McKenna

Harvard University

Abstract:

We consider quadratic forms evaluated at GOE/GUE eigenvectors, like those studied in the context of quantum unique ergodicity. Under a rank assumption, we show that, in order to compute their extremal statistics, it suffices to replace the eigenvectors with independent Gaussian vectors. By carrying out some representative Gaussian computations, we thus find Gumbel and Weibull limiting distributions for the original problem. Joint work with László Erdös.

Contact person:

Gernot Akemann



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  • | Letzte Änderung: 23.11.2011
  •  Olaf Kaczmarek
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