Seminars

The superconformal indeces of 4d SCFTs count their BPS states and, holographically, give information on the microstates of the dual black holes. A possible approach to the exact computation of the index requires solving the so-called Bethe Ansatz equations (BAE). In this talk, I will introduce a rewriting of the BAE in terms of elliptic functions, focusing on the case with 16 supercharges. Such a rewriting permits 1) to quantitatively capture the conjectural relation of BAE with the Calogero-Moser integrable system (and the related continuous solutions) and 2) to rephrase the BAE in terms of configurations of lines on a plane intersecting an elliptic curve.

We consider weighted parallel spinors in
Lorentzian Weyl geometry in arbitrary
dimensions, choosing the weight such
that the integrability condition for the
existence of such a spinor, implies the
geometry to be Einstein-Weyl. We then
use techniques developed for the
classification of supersymmetric
solutions to supergravity theories to
characterise those Lorentzian EW
geometries that allow for a weighted
parallel spinor, calling the resulting
geometries supersymmetric. The overall
result is that they are either
conformally related to ordinary
geometries admitting parallel spinors
(w.r.t. the Levi-Civita connection) or
are conformally related to certain Kundt
spacetime. A full characterisation is
obtained for the 4 and 6 dimensional cases.

After a brief survey of multi-centered black hole physics, I will present some recent developments and advances in this field.

I will report on the classification of 2-ctr. extremal black hole charge configurations through duality-invariant homogeneous
polynomials, which are the generalization of the unique invariant quartic polynomial of the 1-ctr. case. A crucial role is played by an
horizontal SL(p,R) symmetry group, which classifies invariants for p-ctr. black holes. For p=2, the horizontal-invariant with the lowest
degree in charges is the symplectic product <Q1,Q2>, known to control the mutual non-locality of the two centers.
Within U-duality groups "of type E7", both reducible and irreducible symmetric supergravity models in four space-time dimensions will be
considered, thus encompassing N = 2 "magical" and N = 8 maximal theories.

Some basic references are
1] arXiv:1011.5864 [hep-th]
2] arXiv:1101.3496 [hep-th]
3] arXiv:1104.4652 [hep-th]
4] arXiv:1110.4004 [hep-th].

I will review the general construction
of non-extremal black-hole solutions of
N=2,d=4 supergravity coupled to vector
multiplets, and their properties. I will
describe the explicit solutions of a few
models, their extremal (supersymmetric
and non-supersymmetric) limits,
entropies, non-extremality functions etc.

We analyse the vacuum structure of isotropic Z2 X Z2 flux compactifications, allowing for a single set of sources. Combining algebraic geometry with supergravity techniques, we are able to classify all vacua for both type IIA and IIB backgrounds with arbitrary gauge and geometric fluxes.
Surprisingly, geometric IIA compactifications lead to a unique theory with four different vacua. In this case we also perform the general analysis allowing for sources compatible with minimal supersymmetry. Moreover, some relevant examples of type IIB non-geometric compactifications are studied. The computation of the full N=4 mass spectrum reveals the presence of a number of non-supersymmetric and nevertheless stable AdS4 vacua. In addition we find a novel dS4 solution based on a non-semisimple gauging.

We construct explicit type II backgrounds containing squashed and warped anti-de Sitter spaces. These are obtained via T-duality from backgrounds with RR fields. We discuss their properties, including supersymmetry, hidden symmetries and classical integrability (without RR
fields).

Black holes in the isolated and stationary spacetimes have been
intensively studied so far.
They are completely characterized by conserved charges and exhausted
by Kerr family.
Black holes in non-isolated and dynamical background, on the other
hand, have been less understood.
In particular, the black-hole spacetime which is asymptotically FRW
universe is of importance
when discussing formation and evaporation of primordial black holes.
In this talk, I will give a study on the causal structure of `black
hole candidate' recently obtained by Ohta et al,
which is specified by a set of harmonic functions.
We established that this is the first realization of black hole in an
decelerating universe satisfying appropriate physical conditions.
This solution can be generalized to an arbitrary power law expansion
and to any number of dimensions.
We discuss physical properties and causal structures.

We investigate the near horizon geometry of IIB supergravity black
holes with non-vanishing 5-form flux preserving at least two
supersymmetries. It is shown that there are three classes of solutions
distinguished by the choice of Killing spinors. We find that the
spatial horizon sections of the class of solutions with an SU(4) invariant pure
Killing spinor are hermitian manifolds and admit a hidden
Kahler with torsion geometry compatible with the SU(4) structure.
A number of examples of solutions will be given.

I discuss holographic fluids that live on background non-trivial stationary metrics. Using the Randers form of the metric we describe fluids with non-trivial vorticity. Using the Zermelo form of the metric we describe wave propagation in a flowing medium. As an example I discuss the generic Kerr-Taub-NUT AdS4 metrics and show that they provide the holographic description of cyclonic and vortex flow of 2+1 dimensional perfect fluids.

I will talk about covariantly constant forms and almost product structures on torsionful geometries from both world-sheet and space time perspectives, and will discuss the importance of such non-integrable product structures for locally non-geometric compactifications of string theory. the talk is based on arxiv:1004.2824 and arxiv:0906.2028

We discuss the possible stability of non-supersymmetric vacua of D=4 supergravity. First we review what is known about dS and non-SUSY AdS in different theories, and point out relations between these. In the main part of the talk we explain how one to make general statements on this issue, and generalise this to extended supergravities.