November 2014  
Mo 
03.11.2014
Sitzungszimmer Mathematik
Theoretische Physik

14:15 
We show that Liouville integrable Hamiltonian systems with oneandahalf degree of freedom can be described by the method of hydrodynamic reductions. The key object is the Vlasov kinetic equation. Kontakt:
K.H. Rehren

Mi 
05.11.2014
Seminarraum A 03.101
Theoretische Physik

12:00 
Statistische Mechanik komplexer Systeme (Forschungsseminar M.Phy.410)
Abhinav Sharma 3rd Institute of Physics  Biophysics, Göttingen
Elastic response of Filamentous networks and their remodeling in presence of active forces My talk will consist of two parts. First I focus on composite networks. Experiments have shown that elasticity of disordered filamentous networks with compliant crosslinks is very different from networks with rigid crosslinks. Filamentous networks are modeled as a collection of randomly oriented rigid filaments connected to each other by flexible crosslinks that are modeled as wormlike chains. We show that for sufficiently high crosslink density, the network linear elastic response is affine on the scale of the filaments’ length. The nonlinear regime can become highly nonaffine and is characterized by a divergence of the elastic modulus at finite strain. In contrast to the prior predictions, we do not find an asymptotic regime in which the differential elastic modulus scales linearly with the stress, although an approximate linear dependence can be seen in a transition from entropic to enthalpic regimes. In the second part of my talk I focus on remodeling of networks in presence of active forces. First we show experimentally that myosin motors contract crosslinked actin polymer networks to clusters with a scalefree size distribution. This critical behaviour occurs over an unexpectedly broad range of crosslink concentrations. To understand this robustness, we developed a quantitative model of contractile networks that takes into account network restructuring: motors reduce connectivity by forcing crosslinks to unbind. Paradoxically, to coordinate global contractions, motor activity should be low. Otherwise, motors drive initially wellconnected networks to a critical state where ruptures form across the entire network. Kontakt:
Marcus Müller

Mi 
05.11.2014
Seminarraum A 03.101
Theoretische Physik

12:00 
Kontakt:
Marcus Müller

Fr 
07.11.2014
SR 4, Institut für Theoretische Physik, A03.101
SFB 937

14:00 
Seminar
Roland Netz FU Berlin
DNA dynamics, protein force spectroscopy and viscoelastic properties of polymeric networks Kontakt:
Glormann

Mo 
10.11.2014
Seminarraum A.04.101
Theoretische Physik

14:15 
Quantenfeldtheorie (Forschungsseminar M.Phy.412)
Michael Kiessling Rutgers Univ. New Brunswick
The Dirac equation and the KerrNewman spacetime I present results obtained jointly with A. Shadi TahvildarZadeh. They concern Dirac's equation for a point electron in the maximal analytically extended KerrNewman spacetime in its "zerogravity limit." In contrast to other "zerogravity" works, our limit does not yield Minkowski's spacetime decorated with the Appell electromagnetic fields with a physically morethanquestionable ultrasingular "disk source", but instead we obtain a topologically nontrivial Sommerfeld space with meromorphic AppellSommerfeld fields that diverge mildly at a ring singularity (boundary of the abovementioned disk). I explain that the Dirac equation is wellposed on this spacetime in the sense that its associated Hamiltonian is essentially selfadjoint, its spectrum is symmetric, consisting of a continuum with a gap centered at zero in which a discrete spectrum is located if two smallness conditions are met. Some generalizations are addressed also. Finally I explain why our work sheds a new light on some of the most enigmatic aspects of the Dirac equation. Kontakt:
K.H. Rehren

Do 
13.11.2014
Sitzungssaal Mathematik
Theoretische Physik

15:15 
A lot of interesting physical and mathematical information about quantum gases at zero temperature in large volume is encoded in the spectral properties of their Hamiltonian and their total momentum. The joint spectrum of these commuting selfadjoint operators can be called the excitation spectrum. One can conjecture that in some situations the excitation spectrum should have an interesting shape characterized by a positive critical velocity, which is related to superfluidity. In my lectures I will discuss heuristic arguments, approximate approaches and rigorous results about excitation spectrum of the Bose interacting gas. Kontakt:
K.H. Rehren

Fr 
14.11.2014
Theoretische Physik

14:00 
Workshop
D. Bahns, L. Covi, K.H. Rehren
35th LQP Workshop "Foundations and Constructive Aspects of QFT" Kontakt:
K.H. Rehren

Mo 
17.11.2014
Sitzungszimmer Mathematik
Theoretische Physik

14:15 
A proof of asymptotic completeness of scattering theory for manybody Schroedinger operators has been obtained in the late 80's and early 90's, with contributions of Enss, Sigal, Soffer, Graf and myself. In my opinion it is one of the gems of mathematical physics. It has an interesting history. In my talk I would like to recall the formulation of the problem and sketch various attempts to prove it, including the successful one. Kontakt:
K.H. Rehren

Di 
18.11.2014
SR 3, Institut für Theoretische Physik, A03.101
SFB 937

17:15 
Seminar
Frieder Mugele University of Twente (NL)
TBA Kontakt:
Glormann

Do 
20.11.2014
Seminarraum A 03.101
Theoretische Physik

12:00 
Statistische Mechanik komplexer Systeme (Forschungsseminar M.Phy.410)
Guojie Zhang MPI Mainz
Hierarchical Modeling of Highly Entangled Polymer Melts: Kontakt:
Marcus Müller

Do 
20.11.2014
Sitzungssaal Mathematik
Theoretische Physik

15:15 
Motivated by theoretical models in condensed matter physics. We are looking at index theory and spectral flow for operators with essential spectrum (and possibly no discrete spectrum). This talk will survey some of the older and more recent research on this issue. Kontakt:
K.H. Rehren

Mo 
24.11.2014
Seminarraum A.04.101
Theoretische Physik

14:15 
Quantenfeldtheorie (Forschungsseminar M.Phy.412)
Simone Dresti Göttingen
TBA Kontakt:
K.H. Rehren

Di 
25.11.2014
Seminarraum A3.101
Theoretische Physik

14:15 
Theoretischphysikalisches Seminar
Herbert Spohn TU München
Equilibrium time correlations for anharmonic chains Since the 1970ies it has been recognized that onedimensional systems generically have anomalous transport. One manifestation is to consider the superdiffusive spreading of sound and heat peak for the time correlations of the conserved quantities in equilibrium. Recently I proposed a nonlinear extension of fluctuating hydrodynamics to capture the large scale behavior of the correlations. In my talk I will explain the basic theoretical construction and compare with molecular dynamics simulations. The theory amounts to a multicomponent extension of the onedimensional KPZ equation. Kontakt:
J. Oberreuter

Dezember 2014  
Mo 
01.12.2014
Sitzungszimmer Mathematik
Theoretische Physik

14:15 
Kontakt:
K.H. Rehren

Di 
02.12.2014
SR 3, Institut für Theoretische Physik, A03.101
SFB 937

17:15 
Seminar
Yael Roichman Tel Aviv University
TBA Kontakt:
Glormann

Mo 
08.12.2014
Seminarraum A.04.101
Theoretische Physik

14:15 
Quantenfeldtheorie (Forschungsseminar M.Phy.412)
Federico Dradi Göttingen
TBA Kontakt:
K.H. Rehren

Mo 
15.12.2014
SR4 oder Sitzungszimmer Mathematik
Theoretische Physik

14:15 
Kontakt:
K.H. Rehren

Di 
16.12.2014
Seminarraum A3.101
Theoretische Physik

14:15 
Theoretischphysikalisches Seminar
Markus Heyl Universität Innsbruck
Manybody localization and quantum ergodicity in disordered longrange Ising model Ergodicity in quantum manybody systems is —despite its fundamental importance — still an open problem. Manybody localization provides a general framework for quantum ergodicity, and may therefore offer important insights. In this talk, it will be shown using both numerical and analytical methods that longrange interacting Ising models with transversefield disorder enter a manybody localized phase at infinite temperature, irrespective of the disorder strength. As a consequence, these systems are nonergodic. To characterize and quantify quantum ergodicity, a measure for distances in Hilbert space will be introduced. It will be shown that in spin1/2 systems it is equivalent to a simple local observable in real space, which can be measured in current experiments of superconducting qubits, polar molecules, Rydberg atoms, and trapped ions. Kontakt:
S. Kehrein

Januar 2015  
Mo 
05.01.2015
Seminarraum A.04.101
Theoretische Physik

14:15 
Quantenfeldtheorie (Forschungsseminar M.Phy.412)
Robert Czechowski Göttingen
TBA Kontakt:
K.H. Rehren

Do 
08.01.2015
Sitzungssaal Mathematik
Theoretische Physik

15:15 
Graduiertenkolleg 1493
Ingo Runkel Hamburg
Orbifolds and spin structures from defects in twodimensional field theories Defects in twodimensional quantum field theories are lines across which fields of the theory may have discontinuities. Such defects are called "topological" if their precise location does not matter when evaluating correlators. Topological defects contain a lot of information about the field theory in question. In this talk I will concentrate on twodimensional topological and conformal field theories, and I would like to explain how two superficially quite different constructions turn out to be closely related when formulated via defects. These are 1) the orbifolding procedure, and 2) building field theories on surfaces with spin structure. Kontakt:
K.H. Rehren

Di 
20.01.2015
Seminarraum A3.101
Theoretische Physik

14:15 
Theoretischphysikalisches Seminar
Robin Steinigeweg Technical University of Braunschweig
Realtime relaxation of currents in spin1/2 chains: Progress by quantum typicality We use the concept of typicality to study the realtime dynamics of spin and energy currents in spin1/2 models in one dimension and at nonzero temperatures [1,2]. These chains are the integrable XXZ chain and a nonintegrable modification due to the presence of a staggered magnetic field oriented in z direction. In the framework of linear response theory, we numerically calculate autocorrelation functions by propagating a single pure state, drawn at random as a typical representative of the full statistical ensemble. By comparing to smallsystem data from exact diagonalization (ED) and existing shorttime data from timedependent density matrix renormalization group (tDMRG), we show that typicality is satisfied in finite systems over a wide range of temperature and is fulfilled in both, integrable and nonintegrable systems. For the integrable case [1], we calculate the longtime dynamics of the spin current and extract the spin Drude weight for large systems outside the range of ED. We particularly provide strong evidence that the hightemperature Drude weight vanishes at the isotropic point. For the nonintegrable case [2], we obtain the full relaxation curve of the energy current and determine the heat conductivity as a function of magnetic field, exchange anisotropy, and temperature. 
Do 
29.01.2015
Sitzungssaal Mathematik
Theoretische Physik

15:15 
The cobordism hypothesis classifies fully local topological field theories. It is an open problem to realize quantum ChernSimons theory as a fully local field theory in this sense. I show how classical ChernSimons theory and its "prequantization" (in the sense of geometric quantization) has a fully local incarnation, and how it implies the need to cancel the quantum anomaly by means of "p1structure" (Atiyah 2framings). I close with an outlook on how this could be used to get the fully local quantum theory. Kontakt:
K.H. Rehren

Februar 2015  
Mo 
23.02.2015
SR4 oder Sitzungszimmer Mathematik
Theoretische Physik

14:15 
Kontakt:
K.H. Rehren
