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String Seminar

Quantum BTZ black hole

The study of quantum effects on black holes including their gravitational backreaction is an important but notoriously hard problem. I will begin by reviewing how the framework of braneworld holography allows to solve it for strongly-coupled quantum conformal fields. Then I will describe a holographic construction of quantum rotating BTZ black holes (quBTZ) using an exact dual four-dimensional bulk solution. Besides yielding the quantum-corrected geometry and the renormalized stress tensor of quBTZ, we use it to show that the quantum black hole entropy, which includes the entanglement of the fields outside the horizon, rather non-trivially satisfies the first law of thermodynamics, while the Bekenstein-Hawking-Wald entropy does not.

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Thermal order in large N conformal gauge theories

Our experience with many physical systems tells us that usually when a symmetry is spontaneously broken at low temperatures, it is restored upon increasing the temperature sufficiently.  The abundance of such systems raises the question of whether this is a universal feature of all quantum systems. In this talk, I will present examples of (3+1)-dimensional non-supersymmetric large N gauge theories which demonstrate violations of the above feature. I will argue that in the N tending to infinity limit, these theories have conformal manifolds which survive under all loop corrections to the beta functions of the couplings. I will show that under certain conditions, a subset of points on such a conformal manifold demonstrates the spontaneous breaking of a global symmetry at all nonzero temperatures. Furthermore, I will demonstrate that this symmetry breaking is accompanied by the Higgsing of a subset of gauge bosons leading the system to be in a persistent Brout-Englert-Higgs phase.
 
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Scrambling in Yang-Mills Theory

We study operators with a bare dimension that grows as N^2 in the large N limit. These operators are labeled by a Young diagram with p long rows, as well as a graph, with p nodes. The dilatation operator describing the mixing of these operators defines a Hamiltonian for excitations hopping on this graph. The scrambling and equilibration of the resulting dynamics is studied. 
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