# String Seminars

This series consists of talks in the area of Superstring Theory.

## Seminar Series Events/Videos

Currently there are no upcoming talks in this series.

## Black hole microstate counting and its macroscopic counterpart III

Friday Jul 09, 2010
Speaker(s):

In this talk I shall describe a general formalism based on $AdS_2/CFT_1$ correspondence that allows us to
systematically calculate the entropy, index and other physical observables of an extremal black hole taking into
account higher derivative and quantum corrections to the action. I shall also describe precise microscopic computation of the same
quantities for a class of supersymmetric extremal black holes and compare this with the prediction of $AdS_2/CFT_1$
correspondence.

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## Black hole microstate counting and its macroscopic counterpart II

Thursday Jul 08, 2010
Speaker(s):

In this talk I shall describe a general formalism based on $AdS_2/CFT_1$ correspondence that allows us to
systematically calculate the entropy, index and other physical observables of an extremal black hole taking into
account higher derivative and quantum corrections to the action. I shall also describe precise microscopic computation of the same
quantities for a class of supersymmetric extremal black holes and compare this with the prediction of $AdS_2/CFT_1$
correspondence.

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## Black hole microstate counting and its macroscopic counterpart I

Wednesday Jul 07, 2010
Speaker(s):

In this talk I shall describe a general formalism based on $AdS_2/CFT_1$ correspondence that allows us to systematically calculate the entropy, index and other physical observables of an extremal black hole taking into account higher derivative and quantum corrections to the action. I shall also describe precise microscopic computation of the same quantities for a class of supersymmetric extremal black holes and compare this with the prediction of $AdS_2/CFT_1$ correspondence.

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## Probe Branes, time dependent couplings and thermallization in AdS/CFT

Tuesday Jun 08, 2010
Speaker(s):

We study time dependent couplings in conformal field theories using rotating probe branes in AdS X S spacetimes. We find that induced metrics on the brane worldvolumes develop horizons with characteristic Hawking temperatures even when there is no black hole in the bulk. This framework is used to obtain toy models for quantum quench.

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Tuesday Jun 01, 2010
Speaker(s):

Quantization of string theory on the AdS(3) backgrounds with the RR flux, such as AdS(3)xS(3)xT(4) or AdS(3)xS(3)xS(3)xS(1), is an unsolved problem. Since the sigma model on these backgrounds is classically integrable, one can try to implement powerful methods of integrability similar to those used to solve AdS(5)/CFT(4) and AdS(4)/CFT(3). I will describe the integrability approach to the AdS(3) backgrounds, emphasizing the differences to the better understood cases of AdS(5) and AdS(4).

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## Current algebra in conformal sigma models on supergroups (Part II)

Friday May 14, 2010
Speaker(s):

Two-dimensional non-linear sigma models on some supergroup manifolds are conformal field theories whether the action includes a Wess-Zumino term or not. These models are relevant for the worldsheet description of string theory in Anti-de Sitter backgrounds with Ramond-Ramond fluxes. The current algebra is an useful tool to study these theories. In these lectures I will review the construction of the current algebra. Then I will discuss some applications to the computation of the spectrum and integrability.

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## Current algebra in conformal sigma models on supergroups (Part I)

Wednesday May 12, 2010
Speaker(s):

Two-dimensional non-linear sigma models on some supergroup manifolds
are conformal field theories whether the action includes a Wess-Zumino
term or not. These models are relevant for the worldsheet description
of string theory in Anti-de Sitter backgrounds with Ramond-Ramond
fluxes. The current algebra is an useful tool to study these theories.
In these lectures I will review the construction of the current
algebra. Then I will discuss some applications to the computation of
the spectrum and integrability.

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Scientific Areas:

## Gravity dual of spatially modulated phase

Tuesday May 11, 2010
Speaker(s):

In this talk, I will show that the five-dimensional Maxwell theory with a Chern-Simons coupling larger than a critical value in the Reissner-Nordstrom black hole geometry has tachyonic modes. This instability has an interesting property that it happens only at non-vanishing momenta, suggesting a spatially modulated phase transition in the holographically dual field theory. The final state after the phase transition has taken place will be discussed in detail in a special limit

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## Dressing factor in the integrable AdS/CFT system

Tuesday May 04, 2010
Speaker(s):

The seminar is devoted to the solution of the AdS/CFT spectral problem, both for infinite and finite volume cases, using integrability. The basic constructions will be explained using an analogy with the relativistic O(4) sigma model. We devote a special attention to the study of the so called dressing factor. This is a scalar factor of the scattering matrix fixed using discrete crossing symmetry.

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## Instantons and conformal blocks

Tuesday Apr 27, 2010
Speaker(s):

A systematic method to construct 4d N=2 supersymmetric theories by compactifying M5-branes on a Riemann surface was found by Gaiotto last year.
This suggests that any physical quantity of the 4d theory should be reflected in another physical quantity of the 2d theory living on the Riemann surface.
Indeed, one finds that the instanton partition function of the 4d theories equals the conformal blocks of the 2d theory.
I would like to illustrate this construction through explicit examples.

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## RECENT PUBLIC LECTURE

### Mario Livio: Brilliant Blunders

Speaker: Mario Livio