Thema:

Molecular-level ionizing-radiation matter interactions and their consequences

Datum:

13.12.22

Uhrzeit:

14:15

Ort:

H6

Vortragender:

Prof. Dr. Arno Ehresmann

Universität Kassel

Inhalt:

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.

Ansprechpartner:

T. Kuschel

Thema:

tba

Datum:

13.01.23

Uhrzeit:

16:15

Ort:

D5-153

Vortragender:

Felix Finster

Universität Regensburg

Inhalt:

Ansprechpartner:

G. Akemann

Thema:

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

Datum:

12.12.22

Uhrzeit:

16:15

Ort:

D6-135

Vortragender:

Prerna Rana

TIFR Mumbai

Inhalt:

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.

Ansprechpartner:

D. Schwarz

Thema:

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

Datum:

09.12.22

Uhrzeit:

14:15

Ort:

D5-153

Vortragender:

Regina Finsterhölzl

Universität Konstanz

Inhalt:

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.

Ansprechpartner:

FOR2692/Jürgen Schnack

Thema:

tba

Datum:

19.01.23

Uhrzeit:

16:00

Ort:

D5-153

Vortragender:

Tobias Hartung

University of Bath

Inhalt:

Ansprechpartner:

Gernot Akemann

Thema:

Moments and SU(N) algebra for Embedded Unitary Ensemble

Datum:

07.12.22

Uhrzeit:

09:00

Ort:

ZOOM / Konferenzschaltung

Vortragender:

V.K.B. Kota

Physical Research Laboratory Ahmedabad

Inhalt:

Embedded random matrix ensembles with $k$-body interactions, usually called EE($k$), introduced 50 years back in the context of nuclear shell model, are now well established to be appropriate for understanding statistical properties of many quantum systems [1]. Say $m$ fermions (or bosons) are in $N$ degenerate single particle states and interacting with $k$-body interactions. Then, with direct product representation of the many-particle states, the $k$ and $m$ fermion space dimensions are $\binom{N}{k}$ and $\binom{N}{m}$ respectively. Now, with a GUE representation for the Hamiltonian ($H$) matrix in the $k$ particle space, the $m$-particle $H$ matrix will be EGUE($k$) - embedded GUE with $k$-body interactions. Similarly, we have EGOE($k$) and EGSE($k$). Note that for $k=m$ we have the classical GOE, GUE and GSE. Recently, using the formulas for the moments up to order 8, it is established that the one-point function, ensemble averaged density of eigenvalues, follows the so called $q$-normal distribution for EGUE($k$) [also for EGOE($k)] with $q$ defined by the fourth moment [2]. The $q$-normal generates Gaussian density for $k << m$ and semi-circle for $k=m$. Unlike the one-point function, till today there is no success in deriving the two-point correlation function for EGUE($k$) or EGOE($k$) even in the limit of $k <

Ansprechpartner:

Mario Kieburg