Jackiw-Teitelboim Gravity from the Karch-Randall Braneworld.

In this Letter, we show that Jackiw-Teitelboim gravity can be naturally realized in the Karch-Randall braneworld. Notably the role of the dilaton in Jackiw-Teitelboim gravity is played by the radion in a suitably orbifolded version of the setup. In the classical entanglement entropy calculation, there is an apparent degeneracy of Ryu-Takayanagi surfaces. We demonstrate how quantum fluctuations of the radion/dilaton resolve this would-be classical puzzle regarding entanglement wedge reconstruction.

Precision Test of Gauge-Gravity Duality with Flavor.

We put AdS/CFT dualities involving probe branes to a precision test. On the holographic side we use a new class of supersymmetric D7-brane embeddings into AdS(5)×S(5), which allow us to describe N=4 super Yang-Mills theory coupled to massive N=2 supersymmetric flavors on S(4). With these embeddings we can compare holographic results to a field theory analysis of the free energy using supersymmetric localization. Localization allows us to get results at strong coupling, and hence to compare in detail to AdS/CFT. We find analytically matching results: a phase transition at the same critical mass in both calculations and matching free energies up to a scheme-dependent constant in both phases.

Holographic dual of an Einstein-Podolsky-Rosen pair has a wormhole.

We construct the holographic dual of two colored quasiparticles in maximally supersymmetric Yang-Mills theory entangled in a color singlet Einstein-Podolsky-Rosen (EPR) pair. In the holographic dual, the entanglement is encoded in a geometry of a nontraversable wormhole on the world sheet of the flux tube connecting the pair. This gives a simple example supporting the recent claim by Maldacena and Susskind that EPR pairs and nontraversable wormholes are equivalent descriptions of the same physics.

String theory embeddings of nonrelativistic field theories and their holographic Horava gravity duals.

We argue that generic nonrelativistic quantum field theories with a holographic description are dual to Horava gravity. We construct explicit examples of this duality embedded in string theory by starting with relativistic dual pairs and taking a nonrelativistic scaling limit.

Holographic Berezinskii-Kosterlitz-Thouless transitions.

We find the first example of a quantum Berenzinskii-Kosterlitz-Thouless (BKT) phase transition in two spatial dimensions via holography. This transition occurs in the D3/D5 system at nonzero density and magnetic field. At any nonzero temperature, the BKT scaling is destroyed and the transition becomes second order with mean-field exponents. We go on to conjecture about the generality of quantum BKT transitions in two spatial dimensions.

Fractional topological insulators in three dimensions.

Topological insulators can be generally defined by a topological field theory with an axion angle θ of 0 or π. In this work, we introduce the concept of fractional topological insulator defined by a fractional axion angle and show that it can be consistent with time reversal T invariance if ground state degeneracies are present. The fractional axion angle can be measured experimentally by the quantized fractional bulk magnetoelectric polarization P3, and a "halved" fractional quantum Hall effect on the surface with Hall conductance of the form σH=p/q e²/2h with p, q odd. In the simplest of these states the electron behaves as a bound state of three fractionally charged "quarks" coupled to a deconfined non-Abelian SU(3) "color" gauge field, where the fractional charge of the quarks changes the quantization condition of P3 and allows fractional values consistent with T invariance.

Relaxing to three dimensions.

We propose a new selection principle for distinguishing among possible vacua that we call the "relaxation principle." The idea is that the Universe will naturally select among possible vacua through its cosmological evolution, and the configuration with the biggest filling fraction is the likeliest. We apply this idea to the question of the number of dimensions of space. We show that under conventional (but higher-dimensional) Friedmann-Robertson-Walker evolution, a universe filled with equal numbers of branes and antibranes will naturally come to be dominated by 3-branes and 7-branes. We show why this might explain the number of dimensions that are experienced in our visible Universe.

Hadron masses and screening from anti-de Sitter space Wilson loops.

We show that in strongly coupled N=4 supersymmetric Yang-Mills conformal theory the binding energy of a heavy and a light quark is independent of the strength of the coupling constant. As a consequence we are able to show that in the presence of light quarks the analog of the QCD string can snap and color charges are screened. The resulting neutral mesons interact with each other only via pion exchange and we estimate the masses of those states.