Black holes may hold the secrets of quantum gravity, though they hide them deep inside their horizons. The standard model of evaporating black holes states that, for most of their lives, the only channel for information to leak out of the horizon is Hawking radiation. But Hawking radiation is extremely faint, which makes black holes rather stable objects in practice, and preclude to probe what happens in their cores. I will explain how the consideration of macroscopic non-local quantum gravity effects changes this picture, dramatically shortening the life of black holes and opening new observational windows.
There is a sector of the two matrix model defined by the SU(2) sector of N=4 super Yang-Mills theory, that reduces to eigenvalue dynamics. An interesting generalization of the usual Van der Monde determinant that plays a role in this description. The observables captured by this description are the BPS operators of the SU(2) sector and include traces of products of both matrices, which are genuine multi matrix observables. These operators are associated to supergravity excitations of string theory.
I will discuss the correlated stability conjecture of Gubser and Mitra, correlating the thermodynamic and dynamic instabilities of black-branes using a new example in Einstein-dilaton gravity. This solution also serves as a counterexample to the general lore that thermalization time in holographic plasmas always goes like τ ~ 1/T
Algebraic geometry supplies tools for solving F-term and D-term equations in N=1 supersymmetric field theories. The vacuum moduli spaces of physically interesting theories often exhibit intricate and intriguing geometric structure. We discuss Calabi-Yau, Grassmannian, and toric signatures. We examine the electroweak sector of the minimal supersymmetric Standard Model (MSSM) as a test bed for our techniques and report on progress toward solving for the complete vacuum geometry.
After a review of the quasinormal mode method for partition function calculation developed by Denef, Hartnoll, and Sachdev, we extend the method to fields with higher spin, to product spaces, and to spaces with non-Dirichlet boundary conditions.
In this talk we review our recent work on metastring theory and its habitat, a new form of quantum spacetime, called modular spacetime. We emphasize that the geometry underlying modular spacetime, i.e. the background geometry of metastring theory, is also the geometry underlying generic representations of quantum theory as formulated in terms of Aharonov's modular variables. Thus the metastring sheds light on the foundations of quantum theory, and it represents a new formulation of string theory and quantum gravity based on the principle of relative locality. (This work is done in collaboration with Laurent Freidel (Perimeter Institute) and Rob Leigh (Urbana).)
Our light quark jet studies in AdS/CFT reveal that jet dynamics depend sensitively on the currently uncontrolled initial conditions of the corresponding falling string. In order to bring the AdS/CFT initial conditions under control, we compute the energy-momentum tensor associated with the propagation of the classical string solution. Our first calculation of the jet energy-momentum tensor in vacuum using strong-coupling techniques shows the virtuality dependence of the energy density distribution over the full 3D space; as expected the energy of more highly virtual jet is spread over wider angles. Additionally, after a short time after creation of a light q-qbar pair, the energy density is time independent: after the first few moments of propagation, the dual jet does not lose energy. We are currently working on the jet energy density in AdS-Sch background which has more numerical difficulties. With the energy- momentum tensor in hand, we should be able to compute directly from the string theory the actual quantities measured experimentally. (This work is done in collaboration with Will Horowitz (UCT).)
In the first part of my talk I will introduce the definition of Rényi entropy in quantum field theories, and review basic aspects of the so-called Casini-Huerta-Myers prescription employed to holographically compute Rényi entropy. The second part of the talk is devoted to the analysis of the phase transitions in gravity theories with higher derivative corrections (Lovelock gravity theories) and their implications in the holographic Rényi entropy.
After a brief review of 3d Chern-Simons vector models and various supersymmetric and non-supersymmetric dualities among them we will discuss monopole operators in U(Nc) Chern-Simons-matter theories. We mention an apparent problem in the matching of such operators in dualities between non-supersymmetric theories. A similar apparent problem exists in the mapping of chiral monopole operators in theories with N = 2 supersymmetry. We show that in many theories the lowest naive chiral monopole operator is actually not chiral, and we find the lowest monopole operator that is actually chiral in these theories. Since we use the supersymmetric index to find the lowest chiral monopoles, our results for these monopoles are guaranteed to be invariant under the dualities in supersymmetric theories. In the non-supersymmetric dualities the resolution works out in a interestingly way, which we explain. The theories we discuss are believed to be dual in the ’t Hooft large Nc limit to classical high-spin gravity theories. We argue that these theories (supersymmetric or not) should not have classical solutions charged under the U(1) gauge field in the high-spin multiplet.
We use holography to investigate the scrambling properties of various physical systems. Specifically, we consider: (i) non-conformal backgrounds of black Dp branes, (ii) asymptotically Lifshitz black holes, and (iii) black AdS solutions of Gauss-Bonnet gravity. We use the disruption of the entanglement entropy as a probe of the chaotic features of such systems. Our analysis shows that these theories share the same type of behavior as conformal theories as they undergo chaos, however, in the case of Gauss-Bonnet gravity, we find a stark difference in the evolution of the mutual information for negative Gauss-Bonnet coupling. This may signal an inconsistency of the latter.
We investigate the poles of the retarded Green’s functions of strongly coupled field theories exhibiting a variety of phase structures from a crossover up to different first order phase transitions. These theories are modeled by a dual gravitational description. The poles of the holographic Green’s functions appear at the frequencies of the quasinormal modes of the dual black hole background. We focus on quantifying linearized level dynamical response of the system in the critical region of phase diagram. Generically non-hydrodynamic degrees of freedom are important for the low energy physics in the vicinity of a phase transition. For a model with linear confinement in the meson spectrum we find degeneracy of hydrodynamic and non-hydrodynamic modes close to the minimal black hole temperature, and we establish a region of temperatures with unstable non-hydrodynamic modes in a branch of black hole solutions.
The mapping between four-dimensional scalar conformal field theory and a two-dimensional topological field theory (TFT2) has been developed previously [1], [2]. The SO(4, 2) symmetry of the CFT4 appears as a global symmetry of the TFT2. The two key features that make this map possible is the combinatorics of Wick contractions and the observation that the two-point function of the CFT4 can be used as a generator for the TFT2 mapping from two circles to the vaccum. Using these a consistent set of maps satisfying the TFT axioms can be defined. The space of local CFT operators determines the state space of the TFT2 and correlators of local operators can be expressed in terms of TFT2 amplitudes.
A natural extension of this formalism is to include fermions and in this talk it will be shown how the formalism may be generalised to include fields of arbitrary spin. As is the case for scalar field theory this can be understood as a categorised form of classical invariance theory for so(4, 2) representations.
[1] R de Mello Koch, S Ramgoolam, "CFT4 as SO(4,2) invariant TFT2", Nucl.Phys. B890 (2014) 302-349
[2] R de Mello Koch, S Ramgoolam, "Interactions as conformal intertwiners in 4D QFT", 10.1007/JHEP03(2016)165
I will discuss the Hopf algebra symmetry underlying the Leigh-Strassler deformations of N=4 SYM. On the gauge theory side, this symmetry can be expressed via an appropriate star product between the scalar superfields of N=4 SYM. The same star product can be adapted to deform the dual AdS/CFT background in its generalised geometry description. This allows us to construct the dual geometry to certain integrable gauge theories with N=1 supersymmetry. I will point out the challenges in extending the method to the generic, non-integrable case.
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