http://inspirehep.net/record/499969/files/arXiv:hep-th_9905111.pdf

Large N Field Theories, String Theory and Gravity

The authors study in detail the quantum mechanical model of $N$ Majorana fermions with random interactions of a few fermions at a time (Sachdev-Ye-Kitaev model) in the large $N$ limit. At low energies, the system is strongly interacting and an emergent conformal symmetry develops. Performing technical calculations, the authors elucidate a number of properties of the model near the conformal point.

Remarks on the Sachdev-Ye-Kitaev model

We study a two dimensional dilaton gravity system, recently examined by Almheiri and Polchinski, which describes near extremal black holes, or more generally, nearly $AdS_2$ spacetimes. The asymptotic symmetries of $AdS_2$ are all the time reparametrizations of the boundary. These symmetries are spontaneously broken by the $AdS_2$ geometry and they are explicitly broken by the small deformation away from $AdS_2$. This pattern of spontaneous plus explicit symmetry breaking governs the gravitational backreaction of the system. It determines several gravitational properties such as the linear in temperature dependence of the near extremal entropy as well as the gravitational corrections to correlation functions. These corrections include the ones determining the growth of out of time order correlators that is indicative of chaos. These gravitational aspects can be described in terms of a Schwarzian derivative effective action for a reparametrization.

Conformal symmetry and its breaking in two dimensional Nearly Anti-de-Sitter space

In the classical theory black holes can only absorb and not emit particles. However it is shown that quantum mechanical effects cause black holes to create and emit particles as if they were hot bodies with temperature$\frac{{h\kappa }}{{2\pi k}} \approx 10^{ - 6} \left( {\frac{{M_ \odot }}{M}} \right){}^ \circ K$ where κ is the surface gravity of the black hole. This thermal emission leads to a slow decrease in the mass of the black hole and to its eventual disappearance: any primordial black hole of mass less than about 1015 g would have evaporated by now. Although these quantum effects violate the classical law that the area of the event horizon of a black hole cannot decrease, there remains a Generalized Second Law:S+1/4A never decreases whereS is the entropy of matter outside black holes andA is the sum of the surface areas of the event horizons. This shows that gravitational collapse converts the baryons and leptons in the collapsing body into entropy. It is tempting to speculate that this might be the reason why the Universe contains so much entropy per baryon.

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Particle Creation by Black Holes

All purely bosonic supersymmetric solutions of minimal supergravity in five dimensions are classified. The solutions preserve either one half or all of the supersymmetry. Explicit examples of new solutions are given, including a large family of plane-fronted waves and a maximally supersymmetric analogue of the Godel universe which lifts to a solution of 11-dimensional supergravity that preserves 20 supersymmetries.

All supersymmetric solutions of minimal supergravity in five- dimensions

Some general aspects of the AdS 2/CFT1 correspondence, previously discussed in hep-th/9812073, are summarized. The majority of this summary is devoted to the question of where the CFT1 should live. Almost as a byproduct, the decay—or fragmentation—of AdS 2 is also discussed.

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Anti-De Sitter Fragmentation

Some general aspects of the AdS_2/CFT_1 correspondence, previously discussed in hep-th/9812073, are summarized. The majority of this summary is devoted to the question of where the CFT_1 should live. Almost as a byproduct, the decay---or fragmentation---of AdS_2 is also discussed.

/pdf/anti-de-sitter-fragmentation-324p01ju50.pdf

Anti-de Sitter Fragmentation

Anti-de Sitter fragmentation

N-particle quantum mechanics described by a sigma model with an N-dimensional target space with torsion is considered. It is shown that an SL(2,ℝ) conformal symmetry exists if and only if the geometry admits a homothetic Killing vector D a δ a whose associated one-form D a dX a is closed. Further, the SL(2,ℝ) can always be extended to Osp(1|2) superconformal symmetry, with a suitable choice of torsion, by the addition of N real fermions. Extension to SU(1,1|1) requires a complex structure I and a holomorphic U(1) isometry D a I a b δ b . Conditions for extension to the superconformal group D(2,1;α), which involve a triplet of complex structures and SU(2)×SU(2) isometries, are derived. Examples are given.

The Geometry of¶(Super) Conformal Quantum Mechanics

The problem of unifying quantum mechanics and gravity is one of the great unsolved problems in twentieth century physics. Progress has been slowed by our inability to carry out relevant physical experiments. Some progress has nevertheless been possible, largely throught the use of gedanken experiments.

Jeremy Michelson

Papers

Anti-De Sitter Fragmentation

Anti-de Sitter Fragmentation

Anti-de Sitter fragmentation

The Geometry of¶(Super) Conformal Quantum Mechanics

Lectures on Superconformal Quantum Mechanics and Multi-Black Hole Moduli Spaces