Holography Seminar
Time and place: Tue 2-4 pm, Fisher Room, DWB (additional seminars and non-standard time are listed in bold)
Hilary Term 2016 Talks:
- 19/01/2016: No Seminar
- 26/01/2016: No Seminar
- 02/02/2016: Saso Grozdanov (U.Leiden): From holographic transport at finite coupling to bounds on conductivities at strong disorder
Abstract: Holography is a tool that can be most readily applied to studies of transport properties in gauge theories with infinitely strong interactions. Coupling constant corrections can then be incorporated through higher-derivative (alpha-prime) corrections to the supergravity action in the bulk. In the first part of this talk, I will discuss the dependence of higher-order hydrodynamic transport (beyond Navier-Stokes) and the higher-frequency (quasi-normal) spectrum on the coupling constant in duals of Type IIB supergravity and curvature-squared theories. In relation to the membrane paradigm, I will then present higher-order generalisations of the universal "eta over s" relation and universal anomalous conductivities at finite coupling. Recently, studies of holographic transport in the presence of broken translational symmetry and disorder have received much attention. In particular, it has been shown how thermo-electric conductivities can be computed by using the membrane paradigm. Through the power of the membrane paradigm and with a view towards future models of many-body localisation without hydrodynamic transport, in the second part of this talk, I will discuss the proofs of the lower bounds on thermal and electrical conductivities in a large family of holographic theories with arbitrarily strong disorder.
- 08/02/2016 (Monday), 4:30 - 6:30 pm, Seminar room 501 DWB (note the unusual date/time): Adiel Meyer (Tel Aviv U.): Lifshitz Hydrodynamics
Abstract: We derive the constitutive relations of first order charged hydrodynamics for theories with Lifshitz scaling and broken parity in 2+ 1 and 3+ 1 spacetime dimensions. In addition to the anomalous (in 3+1) or Hall (in 2+1) transport of relativistic hydrodynamics, there is an additional non-dissipative transport allowed by the absence of boost invariance. We analyze the non-relativistic limit and use a phenomenological model of a strange metal to argue that these effects can be measured in principle by using electromagnetic fields with non-zero gradients.
- 09/02/2016: Sergey Solodukhin (U. Tours): Conformal anomaly, entanglement entropy and boundaries
Abstract: In my talk I will discuss some new features of conformal anomaly and entanglement entropy in the presence of boundaries.
- 16/02/2016: NO SEMINAR
- 23/02/2016: Jorge Santos (U.Cambridge): Black holes with a single Killing vector field: black resonators
Material: SlidesAbstract: We numerically construct asymptotically anti-de Sitter (AdS) black holes in four dimensions that contain only a single Killing vector field. These solutions, which we coin black resonators, link the superradiant instability of Kerr-AdS to the nonlinear weakly turbulent instability of AdS by connecting the onset of the superradiance instability to smooth, horizonless geometries called geons. Furthermore, they demonstrate non-uniqueness of Kerr-AdS by sharing asymptotic charges. Where black resonators coexist with Kerr-AdS, we find that the black resonators have higher entropy. Nevertheless, we show that black resonators are unstable and comment on the implications for the endpoint of the superradiant instability.
- 25/02/2016 (Thursday), 10:00 - 11:30 am, Beecroft room, DWB (note the unusual date/time): Andrew O'Bannon (U.Southampton): A Monotonicity Theorem for Two-dimensional Boundaries and Defects
Material: SlidesAbstract: I will present a proof for a monotonicity theorem, or c-theorem, for a three-dimensional Conformal Field Theory (CFT) on a space with a boundary, and for a higher-dimensional CFT with a two-dimensional defect. The proof is applicable only to renormalization group flows that preserve locality, reflection positivity, and Euclidean invariance along the boundary or defect, and that are localized at the boundary or defect, such that the bulk theory remains conformal along the flow. The method of proof is a generalization of Komargodski’s proof of Zamolodchikov’s c-theorem. The key ingredient is an external “dilaton” field introduced to match Weyl anomalies between the ultra-violet (UV) and infra-red (IR) fixed points. Reflection positivity in the dilaton’s effective action guarantees that a certain coefficient in the boundary/defect Weyl anomaly must take a value in the UV that is larger than (or equal to) the value in the IR. This boundary/defect c-theorem may have important implications for many theoretical and experimental systems, ranging from graphene to branes in string theory and M-theory.
- 01/03/2016: Aristos Donos (U.Durham): Black Holes, Stokes flows and DC transport at strong coupling
Abstract: Certain materials, such as the cuprate superconductors and heavy fermion materials exhibit fascinating, yet hard to explain transport properties. Holography provides a consistent framework to examine linear response and in particular transport of strongly coupled matter. I will discuss momentum dissipation in holography and show that DC transport is fixed via a Stokes flow of an "auxiliary fluid" residing on the horizon of black holes.
- 08/03/2016: Antonio Garcia-Garcia (U.Cambridge): Universal quantum constraints on the butterfly effect
Material: SlidesAbstract: Lyapunov exponents play an important role in the evolution of quantum chaotic systems in the semiclassical limit. We conjecture the existence of an upper bound on the Lyapunov exponents that contribute to the quantum motion. This is a universal feature in any quantum system or quantum field theory, including those with a gravity dual, at zero or finite temperature. An important consequence of this result is a universal quantum bound on the maximum growth rate of the entanglement entropy.
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.