CCTP Seminars: Fall 2012

### Localizing the black M2-M5 intersection

 Speaker: Vasilis Niarchos Department: University of Crete Slides: [PDF] Time: Tuesday 11 September 2012 at 14:15 Venue: The 2nd floor seminar room of the physics department Abstract: I will discuss recent work on the supergravity description of the fully localized orthogonal black M2-M5 intersection using blackfold theory. An intriguing result for M-theory physics will be reported that pertains to the central charge of the two-dimensional superconformal field theory at the intersection of this system.

### Fermi Surfaces in N=4 Super Yang-Mills

 Speaker: Chris Rosen Department: University of Crete Slides: [PDF] Time: Thursday 13 September 2012 at 11:15 Venue: The 2nd floor seminar room of the physics department Abstract: The construction of Fermi surfaces in the context of holography offers an encouraging avenue into the physics of strongly coupled condensed matter systems. These avenues have, by this time, been well charted. While early efforts demonstrated that only a few key ingredients in the bulk gravitational theory are needed to give rise to a Fermi surface in the boundary theory, these efforts were often unable to determine exactly which boundary theory supported them. In this update, I will briefly outline the study of Fermi surface physics in gauge/gravity duality before providing some relatively new examples of "top-down" Fermi surfaces which arise in N=4 SYM theory via duality.

### Holographic V-QCD at finite temperature

 Speaker: Matti Järvinen Department: University of Crete Slides: [PDF] Time: Tuesday 25 September 2012 at 14:15 Venue: The 2nd floor seminar room of the physics department Abstract: I will first give a review of V-QCD, a set of holographic models for QCD in the Veneziano limit (N_f and N_c large with N_f/N_c=x fixed). These models were introduced recently in [arXiv:1112.1261]. Then I'll discuss ongoing work on the phase diagram of V-QCD at finite temperature. The phase diagram of V-QCD meets the general expectations from field theory both at zero and finite temperature. Depending on the choice of parameters there is, however, variation in the details.

### Moduli Spaces of Cold Holographic Matter

 Speaker: Joao Laia Department: University of Crete Slides: [PDF] Time: Tuesday 2 October 2012 at 14:15 Venue: The 2nd floor seminar room of the physics department Abstract: I will use holography to study (3 + 1)-dimensional N = 4 supersymmetric Yang-Mills theory with gauge group SU(Nc ), in the large-Nc and large-coupling limits, coupled to a single massless (n + 1)-dimensional hypermultiplet in the fundamental representation of SU (Nc ), with n = 3, 2, 1. I will demonstrate that a moduli space exists in these theories, specifically a Higgs branch parameterized by the expectation values of scalar operators bilinear in the hypermultiplet scalars.

### Beauty of scattering amplitudes in gauge theories (department colloquium)

 Speaker: Gregory Korchemsky Department: IPT, Saclay Time: Thursday 4 October 2012 at 17:15 Venue: The 3rd floor seminar room of the physics department Abstract: I will review recent progress in computing scattering amplitudes in strongly coupled gauge theories - a fascinating subject which has been boosted by the formulation of the gauge/string duality in maximally super-symmetric Yang-Mills theory which is considered nowadays as "the simplest gauge theory" and/or harmonic oscillator of 21st century. Thanks to a number of remarkable properties, the scattering amplitudes in this theory can be computed exactly for arbitrary coupling in a suitably defined limit. Quite surprisingly, at strong coupling the problem reduces to finding the minimal surface in a nontrivial geometrical background.

### Higgs-Dilaton Cosmology: From the Early to the Late Universe

 Speaker: Mikhail Shaposhnikov Department: EPFL, Lausanne Slides: [PDF] Time: Monday 8 October 2012 at 15:15 Venue: The 2nd floor seminar room of the physics department Abstract: I will overview the minimal scale-invariant extension of the Standard Model of particle physics combined with Unimodular Gravity. It leads to the evolution of the universe supported by present observations: inflation in the past, followed by the radiation and matter dominated stages and accelerated expansion at present. It solves the problem of baryon asymmetry of the universe, contains a dark matter candidate, and is consistent with neutrino masses and oscillations. All mass scales come from one and the same source. The massless particle spectrum of it contains the graviton and a new particle -- dilaton, which has only derivative couplings and thus escapes the fifth force constraints. A prediction of the Higgs mass and hierarchy problem will be discussed as well.

### Gravitational radiation in ultra-planckian collisions

 Speaker: Theodore Tomaras Department: University of Crete Time: Friday 19 October 2012 at 14:15 Venue: The 2nd floor seminar room of the physics department Abstract: A computation of classical gravitational radiation in massive particle collisions at ultra-planckian energies will be presented in the post-linear formalism of General Relativity and in arbitrary space-time dimensions. The angular and frequency distribution of the radiation as well as the total emitted energy will be discussed. It will be argued that in three or more compact or non-compact extra dimensions most of the available energy is radiated away and should lead to strong radiation friction on the colliding particles.

### On the Large N Limit of Chern-Simons Vector-Models and Three Dimensional Bosonization

 Speaker: Ran Yacoby Department: Weizmann Institute, Tel Aviv Time: Thursday 25 October 2012 at 15:15 Venue: The 2nd floor seminar room of the physics department Abstract: I will review the recent progress in the study of three dimensional U(N)_k Chern-Simons theories coupled to a massless boson or fermion in the fundamental representation. In particular, in the planar limit, one can determine the conformal fixed points and spectrum of local primary operators of these theories. In addition, the planar 3-point functions can be computed exactly as a function of the 't Hooft coupling, and the results agree with the general predictions of Maldacena and Zhiboedov for the correlators of theories that have high-spin symmetries in the large N limit. It has been suggested in the past that the fermionic and bosonic theories are dual to each other at large N. Using the exact expressions of the planar 3-point functions, one can find the precise mapping between the two theories. In particular, it was found that the theory of N scalars coupled to a U(N)_k Chern-Simons theory is equivalent to the Gross-Neveu model of k fermions coupled to a U(k)_N Chern-Simons theory, thus providing a bosonization of the latter theory.

### Quarkonium dissociation by anisotropy in a strongly coupled CFT

 Speaker: Mariano Chernicoff Department: DAMTP, Cambridge Slides: [PDF] Time: Tuesday 30 October 2012 at 14:15 Venue: The 2nd floor seminar room of the physics department Abstract: We compute the screening length for heavy mesons moving through an anisotropic, strongly coupled N=4 super Yang-Mills plasma by means of its gravity dual. We present the results for arbitrary velocities and orientations of the mesons, as well as for arbitrary values of the anisotropy. For generic motion we find that: (i) mesons dissociate above a certain critical value of the anisotropy, even at zero temperature; (ii) there is a limiting velocity for mesons in the plasma, even at zero temperature; (iii) in the ultra-relativistic limit the screening length scales as (1-v2)^{1/2}, in contrast with the isotropic result (1-v2)^{1/4}.

### Supersymmetry on Three-Manifolds

 Speaker: Cyril Closset Department: Weizmann Institute, Tel Aviv Slides: [PDF] Time: Thursday 1 November 2012 at 15:15 Venue: The 2nd floor seminar room of the physics department Abstract: I will explain how to put three-dimensional supersymmetric theories on curved three-manifolds while preserving some supersymmetry. I will discuss some physical implications of this method, including an exact formula for the two-point function of the energy-momentum tensor in 3d N=2 superconformal theories.

### An infalling observer in AdS/CFT

 Speaker: Kyriakos Papadodimas Department: CERN Time: Thursday 8 November 2012 at 15:15 Venue: The 2nd floor seminar room of the physics department Abstract: In the context of AdS/CFT, we attempt to reconstruct the experience of an observer falling behind the horizon of a black hole from the boundary CFT.

### Black holes: alive, kicking and exploding

 Speaker: Vitor Cardoso Department: IST, Lisbon Slides: [PDF] Time: Tuesday 13 November 2012 at 14:15 Venue: The 2nd floor seminar room of the physics department Abstract: Black holes are the elementary particles of gravity, and play a crucial role in fundamental physics, astrophysics, high energy physics and particle physics. In the last 5 years, our ability to understand strongly nonlinear phenomena involving black holes has opened up a new Golden Age in the field. From Cosmic Censorship tests to superkicks and black hole bombs, the possibilities are endless. I will describe some of the current activity in the field along with prospects for the future.

### Classical Limit of Fundamental Strings

 Speaker: Dimitri Skliros Department: University of Nottingham Time: Thursday 22 November 2012 at 15:15 Venue: The 2nd floor seminar room of the physics department Abstract: The classical limit of fundamental strings is a very poorly understood subject area, largely because of the technical difficulty of accessing classical regions with large quantum numbers starting from the perturbative definition of strings, namely the string path integral. And yet, in the cosmic superstring literature it is almost always assumed that macroscopic fundamental strings are classical, and all phenomenological predictions concerning cosmic superstrings are based on this assumption. In this talk I will describe a new approach to this question which is based on identifying macroscopic strings with coherent string states. The use of coherent states largely simplifies the technical challenges of previous approaches, making it possible to go way beyond what has already been achieved with traditional methods. I will discuss decay rates and power in massless radiation (including gravitational waves) for a large class of coherent string states and compare the results with the corresponding classical predictions.

### 3D Super Yang-Mills at Large-N and how to bosonize it

 Speaker: Daniele Dorigoni Department: DAMTP, Cambridge Time: Tuesday 4 December 2012 at 14:15 Venue: The 2nd floor seminar room of the physics department Abstract: In the large N limit, gauge theories compactified on $R^{d-k} \times (S^1)^k$ are independent of the $S^1$ radii, provided that center symmetry remains unbroken. Volume independence holds for arbitrary circle size L, therefore we can match a set of correlation functions in the theory on $R^d$ to the corresponding observables in the reduced $R^{d-k}$ theory. We focus our attention to 3D SYM reduced to 2D and show explicitly how the compact direction is encoded in the color degrees of freedom. By combining volume independence with a non-abelian bosonization procedure we will obtain a bosonized description of the starting 3D theory. As an application we compute the k-string tension and then conclude with some remarks about 4D SYM.

### Log extension of Aging holography and its application to KPZ universality class

 Speaker: Bom Soo Kim Department: Tel Aviv University Slides: [PDF] Time: Tuesday 11 December 2012 at 14:15 Venue: The 2nd floor seminar room of the physics department Abstract: Physics out of equilibrium is interesting and challenging. Aging provides a simple time-dependent setup with local scaling properties in holography as well as in field theory. Motivated by recent experimental realization in KPZ class and further theoretical developments in the context of aging, we study the logarithmic extension of Aging holography. Depending on the parameters in our theory, two-time correlation functions reveal several distinct features of Aging and growth phenomena. The talk includes a pedagogical introduction of the KPZ universality class in some detail.

### Fermi surface, hyperscaling violation and unified frame in effective holographic theories

 Speaker: Bom Soo Kim Department: Tel Aviv University Slides: [PDF] Time: Thursday 13 December 2012 at 15:15 Venue: The 2nd floor seminar room of the physics department Abstract: Fermi surface is one of the most important concepts in condensed matter systems. We give a pedagogical review on recent developments in understanding holographic Fermi surface, along with the role of hyperscaling violation (HSV). While the notion of HSV comes from the condensed matter, it can be also useful to high energy physics. We investigate simple dimensional reduction of various theories and classify lower dimensional effective holographic theories with scaling properties in terms of dynamical and HSV exponent. It turns out that HSV exponent provides a unified framework for the classification. Simple intersecting M2-M5 requires another exponent, we call, spatial anisotropic exponent.