|Mon, 2016-05-23 17:15||(Hörsaal 1 Abbeanum, Fröbelstieg 1 (PAF Kolloquium))|
Prof. Dr. Christian Eggeling, Univ. of Oxford
|Thu, 2016-05-19 14:15||(SR 5, Helmholtzweg 4)|
|Causal Space-time on a Null Lattice|
Prof. Dr. Martin Schaden, Rutgers University
Abstract: I propose a discrete model of Quantum Gravity based on the same principle as the Global Positioning System: the intersection of forward light-cones from four spatially separate events (with some restrictions) determines another event. I show that a causal manifold can thus be described by a topologically hypercubic lattice with light-like links; the length of the spatial diagonal of each plaquette being determined by spinors describing the light-like edges. This lattice model has an SL(2,C) x U^4(1) structure group and is geometric. The description foliates in a causal and physically transparent manner. The observables, the most general local action and the integration measure of this model are all determined by this stucture group and for smooth configurations have well-known continuum limits. Consistency constraints on a configuration to describe a causal manifold are derived and a one-parameter ambiguity of the invariant integration measure is exploited to regularize the model. Finally the SL(2,C) structure group is uniquely localized and the integration measure expressed in terms of geometric invariants. Should time and interest permit, I will also discuss global issues and show numerical results on a small lattice describing the vicinity of the Big Bang in the (unphysical) limit where the cosmological term dominates the dynamics.
|Tue, 2016-05-17 16:15||(SR 5, Helmholtzweg 4)|
| Quantum gravity aspects of black holes |
|Fri, 2016-05-13 10:30||(SR 5, Helmholtzweg 4)|
|Duality between higher spin gravity in (Anti-)deSitter spacetime and conformal field theories|
|Thu, 2016-05-12 14:15|
|Spontaneous breaking of Lorentz symmetry in QED3|
Dr. Lukas Janssen (TU Dresden)
Abstract: The phase diagram of quantum electrodynamics in three space-time dimensions as a function of fermion flavor number N exhibits two well-known phases: at large N > Nc1 the system is in a conformal gapless state, while for small N < Nc2 the fermions are expected to develop a dynamical mass due to spontaneous chiral symmetry breaking. Using epsilon expansion near the lower critical dimension of two, in combination with the recent results on the generalization of the F theorem to continuous dimension, we show that Nc1 > Nc2. There is therefore an intermediate range of values of N at which a third phase is stabilized. We demonstrate that this phase is characterized by spontaneous breaking of Lorentz symmetry, in which a composite vector boson field acquires a vacuum expectation value with the fermions and the photon remaining massless.
|Wed, 2016-05-11 16:15||(HS 2, Abbeanum)|
|Nonequilibrium entropy production for open quantum systems|
Prof. Eric Lutz (FAU Erlangen)
Entropy production is a fundamental quantity of nonequilibrium thermodynamics. We here discuss exact microscopic expressions for the nonequilibrium entropy production of closed and open quantum systems that are driven arbitrarily far from equilibrium, in particular beyond the linear response regime. We additionally consider the entropy production rate, which provides information about the speed of nonequilibrium processes, and show that they are bounded from above for quantum systems. The connection with the notion of quantum speed limit is addressed.
|Wed, 2016-05-04 14:30|
|Quasinormal modes in holographic s-wave superconductors|
von Johanna Mader
|Tue, 2016-05-03 16:15||(SR 5, HHW 4)|
Prof. Dr. Andreas Wipf, TPI Jena
|Mon, 2016-05-02 17:15||(Hörsaal 1 Abbeanum, Fröbelstieg 1 (PAF Kolloquium))|
|Wie entstanden die ersten festen Körper im jungen Sonnensystem?|
Prof. Dr. Jürgen Blum, TU Braunschweig
|Wed, 2016-04-27 16:15|
|Nonlinear evolution of perturbed anti-de Sitter spacetime|
Dr. Piotr Bizon (Krakow)
Abstract: Dynamics of asymptotically AdS spacetimes is an interesting meeting point of fundamental problems in general relativity, PDE theory, theory of turbulence, and AdS/CFT correspondence. In my talk I will describe recent progress in understanding this problem, focusing on evidence for the instability of AdS spacetime.
|Tue, 2016-04-26 17:15||(HS 2, Helmholtzweg 5)|
|Disputation "Untersuchungen von rotierenden und geladenen Staubscheiben mit hochgenauen Näherungslösungen und der Grenzübergang zu Schwarzen Löchern"|
Disputation of Martin Breithaupt
|Tue, 2016-04-26 14:30||(SR 5, Helmholtzweg 4)|
|Thermodynamics of higher spin black holes|
|Thu, 2016-04-21 16:00||(Hörsaal 9, Carl-Zeiß-Str. 3)|
|Magnetic Vortices, vortex lattices and automorphic functions|
Prof. Dr. Israel Michael Sigal, Univ. Toronto
I will review recent results concerning the Ginzburg - Landau equations. These equations were first developed to understand macroscopic behaviour of superconductors; later, together with their non-Abelian generalizations - the Yang-Mills-Higgs equations, they became a key part of the standard model in elementary particle physics. They also have found important applications in geometry and topology.
The Ginzburg - Landau equations have remarkable solutions, localized topological solitons, called the magnetic vortices in the superconductivity and the Nielsen-Olesen or Nambu strings in the particle physics, as well as extended ones, magnetic vortex lattices.
I will review the existence and stability theory of the vortex lattice solutions and how they relate to the modified theta functions appearing in number theory and algebraic geometry. Certain automorphic functions play a key role in the theory described in the talk.
|Thu, 2016-04-21 14:15||(SR 5, Helmholtzweg 4)|
|Critical scaling in the Large-N O(N) model and its possible connection to quantum gravity|
Dr. Péter Mati (Budapest/Szeged)
The critical scaling of the large-N O(N) model in higher dimensions using the exact renormalization group equations will be discussed. Particular attention is paid to the case of d=5 where the scaling exponent of the correlation length has the value 1/3, which coincides with the scaling exponent of quantum gravity in one fewer dimensions. Convincing results show that this relation could be generalized to arbitrary number of dimensions above five. Some aspects of AdS/CFT correspondence will be also discussed.
|Wed, 2016-04-20 10:15||(HI Jena, Fröbelstieg 3)|
|QED in the infrared|
Dr. Péter Mati (Budapest/Szeged)
Joint Seminar with Helmholtz Institute Jena
Infrared (IR) singularities in massless gauge theories are known since the foundation of quantum field theories. The root of this problem can be tracked back to the very definition of these long-range interacting theories such as QED. The IR catastrophe and its resolution by cancelling the divergences will be discussed. The Bloch-Nordsieck model provides the deep IR description of QED, and in its framework all the radiative corrections to the electron propagator can be fully summed, giving the infra-particle interpretation to the electron. This solution can be obtained by using the functional technique based on the Schwinger-Dyson equation with the aid of the Ward-Takahashi identities. At finite temperatures we use the Keldysh description, that will give a matrix structure to the equation. Again an analytic solution can be obtained for the exact spectral function. The finite temperature solution provides a natural explanation of IR finiteness.
|Tue, 2016-04-19 16:15||(SR 5, Helmholtzweg 4)|
|Thermodynamics in GR|
Prof. Dr. Gernot Neugebauer, TPI Jena
|Mon, 2016-04-11 17:15||(Hörsaal 1 Abbeanum, Fröbelstieg 1 (PAF Kolloquium))|
|Habilitationsvorstellung: Verdrilltes Licht: Physik und Anwendungen|
Dr. Marco Ornigotti, Institut für Angewandte Physik, FSU Jena
|Thu, 2016-04-07 14:30||(SR 5, Helmholtzweg 4)|
|Mon, 2016-04-04 17:15||(HS 1, Abbeanum)|
|First Observation of Gravitational Waves from a Binary Black Hole Merger|
Prof. Dr. Bernd Brügmann, FSU Jena
|Fri, 2016-03-11 16:15|
|Collapse of the Brill waves in a moving-puncture-like gauge (WIP)|
One of the open problems in numerical relativity is that of the critical collapse of gravitational waves into a black hole. Quite interestingly, it has been discovered that the supercritical Brill waves, a commonly used family of initial data, cannot be successfully evolved with the moving puncture gauge, popular for black hole simulations. In this talk, we present our work in progress on using a modification of the moving puncture gauge to evolve such data.
|Fri, 2016-03-04 16:15||(HS 2, Abbeanum)|
|Verteidigung der Masterarbeit|