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.

 

Tuesday Feb 19, 2013
Speaker(s): 

We start with a one-slide review of the Kontsevich-Soibelman
(KS) solution to the wall-crossing problem and then proceed to direct  and comprehensive physics counting of BPS states that eventually  connects to KS. We also asks what input data is needed for either  approaches to produce complete BPS spectra, and this naturally  leads to the BPS quiver representation of BPS states and the new notion of quiver invariants.

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Tuesday Feb 05, 2013
Speaker(s): 

I consider a class of
simple classical systems which exhibit motion in their lowest-energy states and thus spontaneously break time-translation symmetry. Their Lagrangians have nonstandard kinetic terms and their Hamiltonians are multivalued functions of momentum, yet they are perfectly consistent and amenable to quantization. Field theoretical generalizations of these systems may have applications in condensed matter physics and cosmology.

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Tuesday Jan 29, 2013
Speaker(s): 

In this talk I investigate the
"firewall argument", that claims that black hole horizons can
not be smooth.

Using
a holographic model of the black hole horizon as a quantum mechanical
membrane, I  show how 

to
recover the black hole interior as an emergent
smooth region of space-time. The reconstruction makes 

use
of the formalism of quantum error correcting codes. I explain
why the horizon of very old black holes 

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Tuesday Jan 22, 2013
Speaker(s): 

A conformal defect is
a d-dimensional geometrical object that breaks the SO(D+1,1) symmetry, of a D-dimensional conformal field theory, down to those transformations that leave the defect invariant i.e. SO(D-d) X SO(d+1,1).

We studied the 3D critical Ising model in presence of a special kind of these defects, a monodromy line defect.

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Tuesday Jan 15, 2013
Speaker(s): 

I
will discuss superhorizon fluctuations in de Sitter space. The first part of
the talk will focus on computing entanglement entropies of field theories in a
fixed de Sitter background. Those computations are done for free theories and
also theories with gravity duals. If time permits, I will also discuss
superhorizon fluctuations in cosmological backgrounds. In particular, I focus
on showing that subhorizon fluctuations can not produce any significant
backreaction on superhorizon modes. If those late time effects existed, one in

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Tuesday Jan 08, 2013
Speaker(s): 

The study of the worldsheet S-matrix for AdS_5×S^5
strings was a key step in

the complete determination of the non-pertubrative planar
spectrum of anomalous

dimensions for N=4 super-Yang-Mills. To go beyond
the spectral problem it is

important to consider higher-point
worldsheet correlation functions and, as is

standard in many integrable models, one approach is
the study of form factors.

We will discuss a set of consistency conditions appropriate
to form factors in

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Tuesday Dec 18, 2012
Speaker(s): 

In this talk we will present results on all one-loop scattering amplitudes in N=6 Chern-Simons matter theories. Especially we will discuss connection between certain triple-cut diagrams and tree-level recursive diagrams, and a general formula capturing the multi-particle factorization of arbitrary one-loop amplitudes in the theories is obtained from this connection. Furthermore a recursion relation for the supercoefficients of one-loop amplitudes will be derived, which leads the solution for all one-loop amplitudes.

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Tuesday Dec 11, 2012
Speaker(s): 

Two-dimensional gauge
theories with (0,2) supersymmetry admit a much broader, and more interesting,
class of solutions than their better studied (2,2) counterparts. In this talk,
we will explore some of the possibilities that are offered by this additional
freedom. The moduli spaces we find can be interpreted as the target spaces for
heterotic strings moving in backgrounds with non-trivial H-flux. A remarkable
relationship between (0,2) gauge anomalies and H-flux will emerge.


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Thursday Dec 06, 2012
Speaker(s): 

The information paradox and the infall problem have been
long-standing puzzles in the understanding of black holes. The idea of free
infall is in considerable tension with unitarity of the evaporation process and
recent developements have made this tension sharp. In the first part of my talk
I will address the information question and argue that unitarty requires every
quantum of radiation leaving the black hole to carry information about the
initial state. Unitary evaporation is thus inconsistent with an

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