**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. |

**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}. |