Aristomenis Donos

Holographic Q-lattices

A bstractWe introduce a new framework for constructing black hole solutions that are holographically dual to strongly coupled field theories with explicitly broken translation invariance. Using a classical gravitational theory with a continuous global symmetry leads to constructions that involve solving ODEs instead of PDEs. We study in detail D = 4 Einstein-Maxwell theory coupled to a complex scalar field with a simple mass term. We construct black holes dual to metallic phases which exhibit a Drude-type peak in the optical conductivity, but there is no evidence of an intermediate scaling that has been reported in other holographic lattice constructions. We also construct black holes dual to insulating phases which exhibit a suppression of spectral weight at low frequencies. We show that the model also admits a novel AdS3 ×

Lifshitz solutions of D=10 and D=11 supergravity

\mathbb{R}

Novel metals and insulators from holography

solution.

Thermoelectric DC conductivities from black hole horizons.

We construct infinite families of Lifshitz solutions of D = 10 and D = 11 supergravity with dynamical exponent z = 2. The new solutions are based on five-and seven-dimensional Einstein manifolds and are dual to field theories with Lifshitz scaling in 1+2 and 1+1 spacetime dimensions, respectively. When the Einstein spaces are Sasaki-Einstein, the solutions are supersymmetric.

Holographic striped phases

A bstractUsing simple holographic models in D = 4 spacetime dimensions we construct black hole solutions dual to d = 3 CFTs at finite charge density with a Q-lattice deformation. At zero temperature we find new ground state solutions, associated with broken translation invariance in either one or both spatial directions, which exhibit insulating or metallic behaviour depending on the parameters of the holographic theory. For low temperatures and small frequencies, the real part of the optical conductivity exhibits a power-law behaviour. We also obtain an expression for the the DC conductivity at finite temperature in terms of horizon data of the black hole solutions.

Wrapped M5-branes, consistent truncations and AdS/CMT

A bstractAn analytic expression for the DC electrical conductivity in terms of black hole horizon data was recently obtained for a class of holographic black holes exhibiting momentum dissipation. We generalise this result to obtain analogous expressions for the DC thermoelectric and thermal conductivities. We illustrate our results using some holographic Q-lattice black holes as well as for some black holes with linear massless axions, in both D = 4 and D = 5 bulk spacetime dimensions, which include both spatially isotropic and anisotropic examples. We show that some recently constructed ground states of holographic Q-lattices, which can be either electrically insulating or metallic, are all thermal insulators.

The thermoelectric properties of inhomogeneous holographic lattices

We discuss new types of instabilities of D = 4 electrically charged AdS-Reissner-Nordström black branes that involve neutral pseudo-scalars. The instabilities spontaneously break translational invariance and are associated with the dual three-dimensional CFTs, at finite temperature and fixed chemical potential with respect to a global abelian symmetry, acquiring striped phases. We show that such instabilities are present for the infinite class of skew-whiffed AdS4 × SE7 solutions of D = 11 supergravity, albeit at a lower temperature than the known superfluid instabilities.

Holographic helical superconductors

At the level of the bosonic fields, we construct consistent Kaluza-Klein reductions of D = 11 supergravity on Σ3 × S4, where Σ3 = H3/Γ, S3/Γ or R3/Γ where Γ is a discrete group of isometries. The result is the bosonic content of an N = 2 D = 4 gauged supergravity with a single vector multiplet and two hypermultiplets, whose scalar fields parametrise SU(1,1)/U(1) × G2(2)/SO(4). When Σ3 = H3/Γ the D = 4 theory has an AdS4 vacuum which uplifts to the known supersymmetric AdS4 × H3/Γ × S4 solution of D = 11 supergravity that describes the N = 2 d = 3 SCFT arising when M5-branes wrap SLag 3-cycles H3/Γ in Calabi-Yau three-folds. We use the KK reduction for Σ3 = H3/Γ to construct D = 11 black hole solutions that describe these d = 3 SCFTs at finite temperature and charge density and show that there is a superconducting instability involving a charged scalar field, and another instability involving neutral fields including both scalar and vector fields. We also use this KK reduction to construct a D = 11 Lifshitz solution that is dual to a d = 3 field theory with dynamical exponent z ∼ 39.

Spatially modulated instabilities of magnetic black branes

A bstractWe consider inhomogeneous, periodic, holographic lattices of D = 4 Einstein-Maxwell theory. We show that the DC thermoelectric conductivity matrix can be expressed analytically in terms of the horizon data of the corresponding black hole solution. We numerically construct such black hole solutions for lattices consisting of one, two and ten wave-numbers. We numerically determine the AC electric conductivity which reveals Drude physics as well as resonances associated with sound modes. No evidence for an intermediate frequency scaling regime is found. All of the monochromatic lattice black holes that we have constructed exhibit scaling behaviour at low temperatures which is consistent with the appearance of AdS2×ℝ2