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 Mar 26, 2013

In the study of the string/gauge theory duality (AdS/CFT), an important role is played by the relation between local operators and Wilson loops. Perhaps the most well known example is the relation between twist two operators and the light-like cusp Wilson loop. On the string side, the twist two operator is represented by a "long" string (GKP). In this talk I use T-duality to argue that such relation is also natural for "short" strings.

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Tuesday Mar 19, 2013

We propose a new
approach for the calculation of the spectrum of excitations of QCD flux tubes.
It relies on the fact that the worldsheet theory is integrable at low energies.
With this approach, energy levels can be calculated for much shorter flux tubes
than was previously possible, allowing for a quantitative comparison with
existing lattice data. The improved theoretical control makes it manifest that
existing lattice data provides strong evidence for a new pseudoscalar particle

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Tuesday Mar 12, 2013

I will discuss the conformal theories of N complex
scalars or fermions in 2+1 dimensions, coupled to a U(N) Chern-Simons (CS)
theory at level k. In the large N limit these theories have a high-spin
symmetry, and, as I will review, they are dual to Vasiliev's high-spin gravity
theories on four dimensional anti-de Sitter space. Maldacena and Zhiboedov
showed that the high-spin symmetry determines the 2-point and 3-point functions
of these theories at large N, up to two parameters. The duality to Vasiliev's

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Tuesday Mar 05, 2013

In this talk, we will describe our recent
work.  Recently, we focus on the thermodynamical property and time
dependence of entanglement entropy. Using holography, we found that the
entanglement entropy for a very small subsystem obeys a property which is
analogous to the first law of thermodynamics when we excite the system. In
relativistic setups, its effective temperature is proportional to the inverse
of the subsystem size. This provides a universal relationship between the

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Tuesday Feb 19, 2013

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

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

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

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

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

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

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

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

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