# Current seminars

In addition to the Vienna relativity seminars, the calendar above sometimes contains other events of interest to members of the relativity group. The seminars of the Vienna relativity group are listed below.

Location (unless indicated otherwise): Währinger Str. 17

- Room 218 on the 2nd floor for **standard seminars**, and

- Common room, first floor, for **lunch seminars**. Unless explicitly stated otherwise, the regular (not-lunch) relativity seminars take place in Room 218 **2nd floor, Währingerstrasse 17.**

The Mathematical Physics Seminars take place on Tuesdays at 14.15.

The Particle Physics Seminars take place on Tuesdays at 16.15.

- Tuesday ,
**September 18th, lunch seminar, 13:00,**

Guilherme Franzmann (Montreal):*Beyond Inflation - a case for string gas cosmology*

Abstract: In this informal talk, we will make a short case against the inflationary paradigm by highlighting some of its problems. In doing so, it will be clear that other alternatives scenarios should also be considered, as for example bouncing cosmologies and emergent quantum gravity proposals. Then we will focus on the latter, in particular in the context of string theory, which prevails being the unique quantum gravity theory that is viable for an unification with the other interactions. We finally discuss String Gas Model and recent developments in the field.

- Tuesday,
**September 25th, 14:00, Seminarraum A**

Oleg Evnin (Bangkok/Brussels):*AdS and Cold Atoms*

Abstract: Taking nonrelativistic limits of field systems in Anti-de Sitter (AdS) spacetime results in variants of the Gross-Pitaevskii equation describing cold atomic gases in harmonic traps (which can be implemented in contemporary terrestrial experiments). This relation underlies the similarities in weakly nonlinear dynamics of these two classes of systems (AdS and atomic gases) whose investigation is normally motivated by rather different physical goals (phenomenology of Bose-Einstein condensation vs. studies of strongly coupled conformal field theories in the context of AdS holography). I will explain how the weakly nonlinear dynamics of such systems is analyzed via the so-called resonant approximation, and present a range of surprising exact results and open questions for the effective nonlinear resonant systems arising from such analysis.

- Wednesday,
**September 26th, 14:00, Seminarraum A**

Oleg Evnin (Bangkok/Brussels):*Quantum resonant systems, integrable and chaotic*

Abstract: Resonant systems emerge as weakly nonlinear approximations to problems with highly resonant linearized perturbations. Examples include nonlinear Schrödinger equations in harmonic potentials and nonlinear dynamics in Anti-de Sitter spacetime. The classical dynamics within this class of systems can be very rich, ranging from fully integrable to chaotic as one changes the values of the mode coupling coefficients. I'll report on investigations of quantum infinite-dimensional resonant systems, which are mathematically a highly special case of two-body interaction Hamiltonians (extensively studied in condensed matter, nuclear and high-energy physics).

Despite the complexity of the corresponding classical dynamics, the quantum version turns out to be remarkably simple, with the Hamiltonian being block-diagonal in the Fock basis, with all blocks of varying finite sizes. Being solvable in terms of diagonalizing finite numerical matrices, these systems are thus arguably the simplest quantum field theories known to man. I'll discuss how to perform the diagonalization in practice, and mention both numerical patterns emerging for the integrable cases, and the spectral statistics, which efficiently distinguishes the special integrable cases from generic (chaotic) points in the parameter space. A wide range of further potential applications can be envisaged, due to the computational simplicity and dynamical richness of quantum resonant systems.

- Thursday,
**September 27th, 15:00, Seminarraum A**

Bob Wald (Chicago):*tba*

** **

Abstract: