Search Talks

Hydrodynamics is the universal theory describing the behavior of fluids when their spacetime variation is on scales longer than any microphysical scale in the fluid. Relativistic hydro has applications in heavy ion collisions and early Universe cosmology, and has seen a surge of interest due to heavy ion experiments and theoretical developments in AdS/CFT. I will explain what second order hydrodynamics is and why it is the minimum theory to study in the relativistic case. Then I discuss some limitations of the theory, including a new bound on how small the viscosity can be and a complication in the rigorous definition of the viscous relaxation time

We formulate a numerical procedure to calculate Hawking radiation during non-equilibrium black hole formation. The procedure is applied to a static string in thermal AdS and it is shown that for an arbitrary initial state, the final state is an equilibrated heavy quark string. The fluctuations in the quark string are transmitted from the horizon to the boundary leading to Brownian motion in the boundary theory.

We discuss holographic duals of strongly interacting gauge theories which show properties of p-wave superfluids which in addition to an Abelian symmetry also break the spatial rotational symmetry. The gravity duals of these superfluid states are black hole solutions with a vector hair which we construct in a non-Abelian Einstein-Yang-Mills theory and in the D3/D7 brane setup. The latter allows us to identify the dual field theory explicitly. After we constructed the vector hair state we study the conductivity and shear viscosity which is non-universal due to the breaking of the rotational symmetry.

I will discuss the collider signatures of heavy, long-lived, neutral particles that decay to charged particles plus missing energy. The focus will be the case of a neutralino NLSP decaying to Z and gravitino within the context of General Gauge Mediation (based on arXiv:1006.4575). I will show that the LHC has the potential for early discovery of such a long-lived particle if its lifetime (c tau) is between about 0.1 millimeters and 100 meters. I will also discuss the use of timing and pointing measurements to fully reconstruct kinematics in events with displaced decays.

The AdS/CFT correspondence relates large-N, planar quantum gauge theories to string theory on the Anti-de-Sitter background. I will discuss exact results in field theories with AdS duals, which can be obtained with the help of diagram resummations, mapping to quantum spin chains and two-dimensional sigma-models.

A remarkable result from heavy ion collisions at the Relativistic Heavy Ion Collider is that shortly after a collision, the medium produced behaves as a nearly ideal liquid. The system is very dynamic and evolves from a state of two colliding nuclei to a liquid in a time roughly equivalent to the time it takes light to cross a proton. Understanding the mechanisms behind the rapid approach to a liquid state is a challenging task. In recent years holography has emerged as a powerful tool to study non-equilibrium phenomena, mapping the (challenging) dynamics of quantum systems onto the dynamics of classical gravitational systems. The creation of a liquid in a quantum theory maps onto the classical process of gravitational collapse and black hole formation. I will describe how one can use holography to study processes which mimic the dynamics of heavy ion collisions.

This talk will focus on hypermultiplet moduli spaces of various N=2 supersymmetric gauge theories in (3+1)d. In the first part of the talk, we discuss the moduli space of instantons on C^2. For the classical groups, the ADHM construction of the moduli space can be realised on the Higgs branch of N=2 gauge theories on D3-branes probing D7-branes. No known construction is available for exceptional groups. We go over the computation of Hilbert series for the one instanton moduli space and show that it is possible to count all chiral operators on the moduli space even though a Lagrangian is not known for exceptional gauge groups. In the second part, we discuss a class of N=2 gauge theories on two M5-branes wrapping Riemann surfaces. This talk will go over Hilbert series for the hypermultiplet moduli space of such theories and show that it is possible to count all chiral operators on the hypermultiplet moduli space for any genus and any number of punctures of the Riemann surface.

We give a detailed derivation of a supersymmetric configuration of wrapped D5-branes on a two-cycle of a warped resolved conifold. Our analysis reveals that the resolved conifold should support a non-Kahler metric with an SU(3) structure. We use this as a starting point of the geometric transition in type IIB theory. A mirror, and a subsequent flop transition using an intermediate M-theory configuration with a G2 structure, gives rise to the complete IR geometric transition in type IIA theory. A further mirror transformation gives the type IIB gravity dual of the IR gauge theory on the wrapped D5-branes. Expectedly non-Kahler deformations of the resolved and the deformed conifolds appear as the gravity duals of the confining gauge theories in type IIA and type IIB theories respectively, although in more generic cases these manifolds could also be non-geometric. In the local limit we reproduce precisely the scenarios presented in our earlier works. Our present work should therefore be viewed as providing a supergravity proof of geometric transitions in the full global scenarios in type II theories.

Large mixing angles and a mild mass hierarchy are observed in neutrino oscillations, in stark contrast with the quarks and charged leptons sectors where very hierarchical masses come along with small mixings. We review and discuss the neutrino mass patterns that are technically natural, in the context of the seesaw mechanism and with a quark-lepton unification perspective. We show that a seesaw in six dimensions offers an elegant and unique solution to the flavor puzzle. An explicit model is constructed, with a vortex background on a sphere. It offers an explanation for the replication of families in the Standard Model, and predicts suppressed flavour violating interactions.

False vacua in QFT are liable to undergo spontaneous decay. Slowness of quantum tunneling can however allow a long lifetime to the false vacuum state. In supersymmetric theories this is a crucial criterion for obtaining a long lived universe with spontaneously broken supersymmetry. We have explored false vacua which admit topological defects, including in a supersymmetric model with O'Rafeartaigh type supersymmetry breaking. We show that the presence of topological defects significantly alters the stability of the false vacuum. For some values of parameters, it also results in the putative false vacuum being rendered unstable. Finally I report a formula derived for instanton assisted tunneling applicable to metastable vacua with monopoles.

Since the dawn of civilization, humans have attempted to dissect the world and uncover its fundamental constituents. Today, this quest continues in the field of particle physics, the study of the fundamental subatomic particle that make up everything in the universe. The Large Hadron Collider (LHC) is a massive underground particle accelerator that physicists hope will reveal new secrets about the physical world. Located just outside Geneva, Switzerland at CERN, it has a circumference of 27 km and is the product of a collaboration that involves thousands of scientists worldwide. This presentation will talk about the LHC and some of the exciting new ideas it may confirm.