Found 5 result(s)

03.02.2016 (Wednesday)

Holographic cosmology and Planck data

Triangular Seminar Kostas Skenderis (Southampton)

at:
16:00 City U.
room AG07b
abstract:

I will present holographic models for the very early Universe, the period usually associated with inflation, and compare the predictions of these models against Planck 2015 data. Within the holographic framework the early Universe is described by a three dimensional QFT. Conventional inflation is included in this framework as strong coupled QFT while qualitatively new models arise when the QFT has weak or intermediate coupling. The weakly coupled models describe a very quantum early Universe and it turns out that these models fit the Planck data remarkably well, providing an alternative to LambdaCDM. New models based on QFT at intermediate coupling may be constructed using Lattice methods and I will also describe on-going work in this direction.

02.04.2014 (Wednesday)

Scale vs conformal invariance in four dimensions

Regular Seminar Kostas Skenderis (STAG, Southampton U.)

at:
14:00 IC
room H503
abstract:

I will discuss the question of whether four dimensional scale invariant unitary quantum field theories are actually conformally invariant. I will present a complete analysis of possible scale anomalies in correlation functions of the trace of the stress-energy tensor in such theories and discuss recent attempts to show that scale invariance implies conformal invariance.

05.12.2012 (Wednesday)

AdS/Ricci-flat correspondence

Regular Seminar Kostas Skenderis (Southampton)

at:
13:15 KCL
room S4.23
abstract:

We show that for every asymptotically AdS solution compactified on a torus there is a corresponding Ricci-flat solution obtained by replacing the torus by a sphere, performing a Weyl rescaling of the metric and appropriately analytically continuing the dimension of the torus/sphere (as in generalized dimensional reduction). This correspondence should allow us to develop a holographic dictionary for Ricci-flat spacetimes. In particular, it maps Minkowski spacetime to AdS on a torus, the holographic stress energy tensor of AdS to the stress energy tensor due to a brane localized in the interior of spacetime and AdS black branes to (asymptotically flat) Schwarzschild black branes. Applying it to the known solutions describing the hydrodynamic regime in AdS/CFT, we compute the dispersion relation of the Gregory-Laflamme unstable modes through cubic order in the wavenumber, finding remarkable agreement with numerical data. We further obtain the fluid dual to Rindler spacetime and show that its transport coefficients through second order follow from the AdS ones.

24.05.2007 (Thursday)

Holographic methods and applications to black holes

Regular Seminar Kostas Skenderis (University of Amsterdam)

at:
13:30 IC
room Huxley 503
abstract:

We discuss how to extract quantum field theory data from solutions that are asympotically (AdS_p x S_q). We apply this method to general 2-charge fuzzball solutions that is, horizon-free non-singular solutions of IIB supergravity characterized by a number of curves. We propose a precise map that relates any given curve to a specific superposition of R ground states of the D1-D5 system. To test this proposal we compute the holographic 1-point functions associated with these solutions, namely the conserved charges and the vacuum expectation values of chiral primary operators of the boundary theory, and find perfect agreement within the approximations used. All kinematical constraints are satisfied and the proposal is compatible with dynamical constraints.

23.03.2006 (Thursday)

Kaluza-Klein Holography

Regular Seminar Kostas Skenderis (Amsterdam)

at:
14:00 QMW
room 112
abstract: