# 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.

## DT-invariants and $K_2$

Thursday Aug 23, 2012
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TBA

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## Resurgence from the path integral perspective

Tuesday Aug 21, 2012
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TBA

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## Universality in all-order alpha' corrections to BPS/non-BPS brane world volume theories

Monday Aug 13, 2012
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Knowledge of all-alpha' higher derivative corrections to leading order BPS and non-BPS brane actions would serve in future endeavor of determining the complete form of the non-abelian BPS and tachyonic effective actions. In this talk, we note that there is a universality in the all-alpha' order corrections to BPS and non-BPS branes. I talk about computing all amplitudes between one Ramond-Ramond C-field vertex operator and several SYM gauge/scalar vertex operators.

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## Chiral Symmetry Breaking via Gauge/Gravity Duality

Thursday Aug 02, 2012
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TBA

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## Holographic Lattices

Tuesday May 29, 2012
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We add a gravitational background lattice to the simplest holographic model of matter at finite density and calculate the optical conductivity. With the lattice, the zero frequency delta function found in previous calculations (resulting from translation invariance) is broadened and the DC conductivity is finite. The optical conductivity exhibits a Drude peak with a cross-over to power-law behavior at higher frequencies. Surprisingly, these results bear a strong resemblance to the properties of some of the cuprates.

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## Background Independent Holographic Description : From Matrix Field Theory to Quantum Gravity

Tuesday May 22, 2012
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A local renormalization group procedure is proposed where length scale is changed in spacetime dependent manner. Combining this scheme with an earlier observation that high energy modes in renormalization group play the role of dynamical sources for low energy modes at each scale, we provide a prescription to derive background independent holographic duals for field theories.

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## On-shell Recursion Relation for String Tree-level Amplitude

Tuesday May 08, 2012
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It is well known that on-shell recursion relation can be applied to tree-level amplitude in string theory. One technical issue of the application is the sum of infinite middle on-shell states. We discuss how we can do the sum exactly to reproduce the known result.

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## Simple Scattering Amplitudes in Higher Dimensions

Tuesday Apr 17, 2012
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TBA

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## K3 Modular Parametrization and Calabi-Yau Threefold Moduli

Tuesday Mar 27, 2012
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A series of generalizations of the Weierstrass normal
form for elliptic curves to the case of K3 surfaces will be presented.  These have already been applied to better
understand F-theory/Heterotic string duality.
We will see how they also resolve a long-standing question of which
"mirror-compatible" variations of Hodge structure over the
thrice-punctured sphere can arise from families of Calabi-Yau threefolds.

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## Instanton - A Window into Physics of M5-branes

Friday Mar 23, 2012
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Instantons and W-bosons in 5d N=2 Yang-Mills theory arise from a circle compactification of the 6d (2,0) theory as Kaluza-Klein modes and winding self-dual strings, respectively. We study an index which counts BPS instantons with electric charges in Coulomb and symmetric phases. We first prove the existence of unique threshold bound state of U(1) instantons for any instanton number. By studying SU(N) self-dual strings in the Coulomb phase, we find novel momentum-carrying degrees on the worldsheet.

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## RECENT PUBLIC LECTURE

### Mario Livio: Brilliant Blunders

Speaker: Mario Livio