Holography Seminar
Time and place: Tue 2-4 pm, Seminar Room 501, DWB (additional seminars and non-standard time are listed in bold)
Trinity Term 2015 Talks:
- 28/04/2015: No Seminar
- 05/05/2015, Video Conference Room, DWB: Mario Flory (Max Planck Institute Munich): Entanglement entropy in a holographic model of the Kondo effect
Abstract: My starting point is a holographic model of the Kondo effect recently proposed by Erdmenger et. al., i.e. of a magnetic impurity interacting with a strongly coupled system. Specifically, I focus on the challenges of computing gravitational backreaction in this model, which demands a study of the Israel junction conditions. I present general results on these junction conditions, including analytical solutions for certain toy models, that may be relevant also more generally in the AdS/boundary CFT correspondence. Furthermore, similar junction conditions for a bulk Chern-Simons field appearing in the holographic Kondo model are discussed. I then focus on the computation and interpretation of entanglement entropy in this holographic model.
- 12/05/2015: Takaaki Ishii: Turbulent strings in AdS/CFT
Abstract: I will describe the nonlinear dynamics of the flux tube between an external quark-antiquark pair in N=4 SYM using the gravity dual given by a string in AdS. I will numerically compute the nonlinear time evolution of the string when the endpoints are perturbed in various ways. As a result, cusps can form on the string. I will then discuss a connection between this phenomenon and turbulent behavior in the energy spectrum. This talk is based on arXiv:1504.02190.
- 19/05/2015: Rakibur Rahman (AEI, Potsdam): Fermion Dipole Moments and Holography
Abstract: In the background of a charged AdS black hole, we consider a Dirac particle endowed with arbitrary dipole moments. For non-zero charge and dipole couplings of the bulk fermion, we find that the dual boundary theory is generically plagued with superluminal modes. Requiring that the dual CFT have no such pathology amounts to constraining the strength of the dipole couplings by an upper bound. Our results are relevant for the physics of holographic non-Fermi liquids.
- 26/05/2015: Javier Mas (U.Santiago de Compostela): Collapse in AdS and Relaxation in Closed Quantum Systems
Material: SlidesAbstract: While the issue about the nonlinear stability of AdS is under intense survey and debate, the numerical work done so far has revealed a rich variety of possible routes towards black hole formation and a strong sensitivity upon initial conditions. In the light of the AdS/CFT correspondence, these should be considered as duals of off-equilibrium relaxation dynamics in strongly coupled quantum systems. With due caution, it makes sense to try to compare salient and robust features with those found in the thermalisation of closed quantum systems. I will review the data we have been accumulating in the case of a massless scalar collapsing in global AdS focusing on solutions which exhibit transient oscillatory behaviour, reminiscent of quantum revivals. I will compare the situation in different dimensions and also comment on the case of non-compact boundary.
- 02/06/2015: Shiroman Prakash (Dayalbagh Educational Institute): Bifundamental Chern Simons Theories and the M/N expansion
Abstract: Two very different large N expansions exist - large N vector models which contain degrees of freedom transforming in the vector representation of a gauge group and large N matrix models which contain degrees of freedom transforming in the adjoint representation of a gauge group. Large N vector models, such as the Gross Neveu model or the critical O(N) model, are exactly solvable in the 't Hooft large N limit; while their dynamics is typically very similar to free theories, or Landau liquids. Large N matrix theories, such as N=4 SYM theory or large N QCD, are not exactly solvable in the large N limit and their dynamics is now known to be potentially much more interesting, particularly at strong coupling, where there is the possibility of a dual gravity description. The M/N expansion is an expansion that takes us from large N vector saddle point to a large N matrix saddle point, and is made possible thanks to the existence of bifundamental Chern-Simons theories, unique to three dimensions. The most well-known bifundamental Chern-Simons theory is ABJM theory, but other interesting non-supersymmetric and conformal examples also exist. In this talk, which is based on 1404.7849 and work by many people over the past few years, I will discuss the landscape of bifundamental Chern-Simons theories and speculate about their possible holographic duals.
- 09/06/2015: Ayan Mukhopadhyay (U.Crete): Semi-holography for QCD
Material:Abstract: I will introduce semi-holography as a novel effective framework at intermediate energy scales for a large class of systems with strong interactions, emphasising that it can predict phenomena with a finite number of parameters. I will discuss how this framework can be applied to the quark-gluon plasma at appropriate range of temperatures, and also to general low energy hadronic and nuclear physics of QCD. We will see that exotic penta-quark states and also saturation phenomena can be naturally embedded in this framework. Finally, I will sketch a fundamental derivation of this framework using a generalisation of Wilsonian RG.
- 16/06/2015, Conference Room, DWB: Lárus Thorlacius (U.Iceland): : Magnetic effects in holographic metals
If you are interested in presenting your research in Oxford, please contact Jonas Probst.
For a list of past talks follow this link.
The following might also be of interest:
- A weekly updated list of talks related to string theory.
- A list of all seminars in the Physics Department, including the Theoretical Physics Colloquium and the Particles and Fields Seminar.