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Aktuelle Veranstaltungen

 

Kolloquium

Thema:

Topological and morphological analysis of random fields with applications to compressible turbulence

Datum:

28.05.18

Uhrzeit:

16:15

Ort:

H6

Vortragender:

Prof. Anvar Shukurov

Newcastle University

Inhalt:

Turbulence plays an important role in determining the random fluctuations in plasmas. The theory of random functions and techniques of data analysis mostly rely on the assumption that the underlying random field follows Gaussian statistics. This limitation is becoming less and less acceptable as the resolution, sensitivity and physical complexity of experimental and numerical data increase. Observations and simulations of compressible random flows, especially in astrophysical contexts, provide a good example of this difficulty. This work is motivated by the need to compare with observations the results of comprehensive simulations of turbulence in the interstellar medium. The quantitative methods used at present are limited to probability densities and Fourier spectra of random fields, which are insensitive to widespread filamentary structures revealed by observations of interstellar gas. We discuss novel methods of data analysis that are applicable to intermittent, strongly non-Gaussian random fields and are based on recent developments in computational topology and morphology or random fields. Particular aspects include the recovery of a three-dimensional structure of a random field from its two-dimensional cross-section and the effects of magnetic field on interstellar turbulence.

Ansprechpartner:

D. Schwarz

Kolloquium Mathematische Physik

Thema:

Upper and lower Lipschitz bounds for the perturbation of edges of the essential spectrum

Datum:

01.06.18

Uhrzeit:

16:15

Ort:

V3-204

Vortragender:

Ivan Veselic

TU Dortmund

Inhalt:

Let $A$ be a selfadjoint operator, $B$ a bounded symmetric operator and $A+t B$ a perturbation. I will present upper and lower Lipschitz bounds on the function of $t$ which locally describes the movement of edges of the essential spectrum. Analogous bounds apply also for eigenvalues within gaps of the essential spectrum. The bounds hold for an optimal range of values of the coupling constant $t$. This is result is applied to Schroedinger operators on unbounded domains which are perturbed by a non-negative potential which is mostly equal to zero. Unique continuation estimates nevertheless ensure quantitative bounds on the lifting of spectral edges due to this semidefinite potential. This allows to perform spectral engineering in certain situations. The talks is based on the preprint https://arxiv.org/abs/1804.07816

Ansprechpartner:

G. Akemann

Seminar Hochenergiephysik

Thema:

The QCD crossover up to O(\mu^6_B) from Lattice QCD

Datum:

29.05.18

Uhrzeit:

14:00

Ort:

D6-135

Vortragender:

Patrick Steinbrecher

Bielefeld University

Inhalt:

Ansprechpartner:

F. Karsch

Seminar Kondensierte Materie

Thema:

Dynamical Typicality in Quantum Statistical Mechanics

Datum:

24.05.18

Uhrzeit:

14:15

Ort:

D5-153

Vortragender:

Ben Niklas Balz

Universität Bielefeld

Inhalt:

Ansprechpartner:

Peter Reimann

Seminar Mathematische Physik

Thema:

Eigenvector-related correlation functions and their connection with generalized chiral random matrix ensembles with a source

Datum:

11.01.18

Uhrzeit:

16:00

Ort:

D5-153

Vortragender:

Jacek Grela

LPTMS Université Paris-Sud

Inhalt:

We will introduce eigenvector-related correlation functions, discuss briefly their significance in dynamical Ginibre ensemble [1,2] and present asymptotic results in the large matrix size limit. Motivated by recent work [3] on joint eigenvector-eigenvalue correlation function valid for finite matrix size N in the complex and real Ginibre Ensembles, we study integrable structure of a certain generalized chiral Gaussian Unitary Ensemble with a source [4]. This model can be also interpreted as a deformation of the complex Ginibre Ensemble with an external source with additional determinant term. We present compact formulas for the characteristic polynomial, inverse characteristic polynomial and the kernel. In the case of a special source, we calculate asymptotics in the joint "bulk-edge" regime of all aforementioned objects and show their Bessel-type behaviour. References: [1] ''Dysonian dynamics of the Ginibre ensemble'', Z. Burda, J. Grela, M. A. Nowak, W. Tarnowski, P. Warcho?, Phys. Rev. Lett. 113, 104102 (2014) [2] ''Unveiling the significance of eigenvectors in diffusing non-hermitian matrices by identifying the underlying Burgers dynamics'', Z. Burda, J. Grela, M. A. Nowak, W. Tarnowski, P. Warcho?, Nucl. Phys. B 897, 421 (2015) [3] ''On statistics of bi-orthogonal eigenvectors in real and complex Ginibre ensembles: combining partial Schur decomposition with supersymmetry'', Y. V. Fyodorov, arXiv:1710.04699 [4] ''On characteristic polynomials for a generalized chiral random matrix ensemble with a source", Y. V. Fyodorov, J. Grela, E. Strahov, arXiv:1711.07061

Ansprechpartner:

Gernot Akemann

Seminar AG Zufallsmatrizen

Thema:

tba

Datum:

27.06.18

Uhrzeit:

16:15

Ort:

V3-201

Vortragender:

Yacin Ameur

Lund University

Inhalt:

Ansprechpartner:

Gernot Akemann



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  • | Letzte Änderung: 23.11.2011
  •  Olaf Kaczmarek
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