arXiv subjects

Aristomenis Donos

Publications and source records attributed to Aristomenis Donos.

At least 55 records · Page 3Linked to original sources

arXiv2014

Novel metals and insulators from holography

Using 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 with broken translation invariance, either in 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 has a power-law behaviour, with the exponent determined by the ground state. We also obtain an expression for the the DC conductivity at finite temperature in terms of horizon data of the black hole solutions.

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arXiv2014

Flowing from $AdS_5$ to $AdS_3$ with $T^{1,1}$

We construct supersymmetric domain wall solutions of type IIB supergravity that interpolate between $AdS_5\times T^{1,1}$ in the UV and $AdS_3\times\mathbb{R}^2\times S^2\times S^3$ solutions in the IR. The $\mathbb{R}^2$ factor can be replaced with a two-torus and then the solution describes a supersymmetric flow across dimensions, similar to wrapped brane solutions. While the domain wall solutions preserve $(0,2)$ supersymmetry, the $AdS_3$ solutions in the IR have an enhanced $(4,2)$ superconformal supersymmetry and are related by two T-dualities to the $AdS_3\times S^3\times S^3\times S^1$ type IIB solutions which preserve a large $(4,4)$ superconformal supersymmetry. The domain wall solutions exist within the $N=4$ $D=5$ gauged supergravity theory that is obtained from a consistent Kaluza-Klein truncation of type IIB supergravity on $T^{1,1}$; a feature driving the flows is that two $D=5$ axion like fields, residing in the $N=4$ Betti multiplet, depend linearly on the two legs of the $\mathbb{R}^2$ factor.

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arXiv2014

Holographic Q-lattices

We 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. 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 $AdS_3\times\mathbb{R}$ solution.

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arXiv2013

Competing p-wave orders

We construct electrically charged, asymptotically $AdS_5$ black hole solutions that are dual to $d=4$ CFTs in a superfluid phase with either p-wave or $(p+ip)$-wave order. The two types of black holes have non-vanishing charged two-form in the bulk and appear at the same critical temperature in the unbroken phase. Both the p-wave and the $(p+ip)$-wave phase can be thermodynamically preferred, depending on the mass and charge of the two-form, and there can also be first order transitions between them. The p-wave black holes have a helical structure and some of them exhibit the phenomenon of pitch inversion as the temperature is decreased. Both the p-wave and the $(p+ip)$-wave black holes have zero entropy density ground states at zero temperature and we identify some new ground states which exhibit scaling symmetry, including a novel scenario for the emergence of conformal symmetry in the IR.

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arXiv2013

Holographic charge density waves

We show that strongly coupled holographic matter at finite charge density can exhibit charge density wave phases which spontaneously break translation invariance while preserving time-reversal and parity invariance. We show that such phases are possible within Einstein-Maxwell-dilaton theory in general spacetime dimensions. We also discuss related spatially modulated phases when there is an additional coupling to a second vector field, possibly with non-zero mass. We discuss how these constructions, and others, should be associated with novel spatially modulated ground states.

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arXiv2013

On the thermodynamics of periodic AdS black branes

We consider asymptotically AdS black brane solutions that are dual to CFTs with periodic dependence on the spatial directions, arising from either a spontaneous or an explicit breaking of translational symmetry. We derive a simple expression for the variation of the free-energy with respect to changing the periods. This explains some observations, based on numerics, that have arisen in the explicit construction of thermodynamically preferred black holes in the case that the spatial directions are infinite in extent and the symmetry is spontaneously broken. It also leads to simple Smarr-type relations involving the boundary stress tensor..

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arXiv2013

Striped phases from holography

We discuss new types of second order phase transitions in holography by constructing striped black holes in D=4 with $AdS_{4}$ asymptotics. In the context of $AdS/CFT$, they provide the gravity duals to field theory phases in which translational symmetry is spontaneously broken due to the formation of current density waves. These black holes are associated to three dimensional CFTs at finite temperature and deformed by a uniform chemical potential. We numerically solve a non-linear system of PDEs in order to construct the black hole geometries and extract some of their thermodynamic properties.

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arXiv2013

Semi-local quantum criticality in string/M-theory

Semi-local quantum critical behaviour in $D-1$ spacetime dimensions can be holographically described by metrics that are conformal to $AdS_2\times\mathbb{R}^{D-2}$, with the conformal factor characterised by a parameter $η$. We analyse such "$η$-geometries" in a top-down setting by focussing on the $U(1)^4$ truncation of D=4 N=8 gauged supergravity. The model has extremal black hole solutions carrying three non-zero electric or magnetic charges which approach $AdS_4$ in the UV and an $η=1$ geometry in the IR. Adding a fourth charge provides a mechanism to resolve the singularity of the $η$-geometry, replacing it with an $AdS_2\times\mathbb{R}^2$ factor in the IR, while maintaining a large region where the $η$-geometry scaling is approximately valid. Some of the magnetically charged black hole solutions preserve supersymmetry while others just preserve it in the IR. Finally, we show that $η$-geometries, with various values of $η$, can be obtained from the dimensional reduction of geometries consisting of $AdS$ or Lifshitz geometries with flat directions.

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arXiv2013

Metal-insulator transition in holography

We exhibit an interaction-driven metal-insulator quantum phase transition in a holographic model. Use of a helical lattice enables us to break translation invariance while preserving homogeneity. The metallic phase is characterized by a sharp Drude peak and a d.c. resistivity that increases with temperature. In the insulating phase the Drude spectral weight is transferred into a `mid-infrared' peak and to energy scales of order the chemical potential. The d.c. resistivity now decreases with temperature. In the metallic phase, operators breaking translation invariance are irrelevant at low energy scales. In the insulating phase, translation symmetry breaking effects are present at low energies. We find the near horizon extremal geometry that captures the insulating physics.

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arXiv2012

Competing orders in M-theory: superfluids, stripes and metamagnetism

We analyse the infinite class of d=3 CFTs dual to skew-whiffed AdS_4 X SE_7 solutions of D=11 supergravity at finite temperature and charge density and in the presence of a magnetic field. We construct black hole solutions corresponding to the unbroken phase, and at zero temperature some of these become dyonic domain walls of an Einstein-Maxwell-pseudo-scalar theory interpolating between AdS_4 in the UV and new families of dyonic AdS_2 X R^2 solutions in the IR. The black holes exhibit both diamagnetic and paramagnetic behaviour. We analyse superfluid and striped instabilities and show that for large enough values of the magnetic field the superfluid instability disappears while the striped instability remains. For larger values of the magnetic field there is also a first-order metamagnetic phase transition and at zero temperature these black hole solutions exhibit hyperscaling violation in the IR with dynamical exponent z=3/2 and θ=-2.

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arXiv2012

Supersymmetric quantum criticality supported by baryonic charges

In the context of the $AdS_4\times Q^{111}$ solution of D=11 supergravity we construct supersymmetric zero temperature black brane solutions that interpolate between $AdS_4$ in the UV and $AdS_2\times \mathbb{R}^2$ in the IR. The dual N=2 SCFT has a $U(1)^2$ baryonic symmetry and the solutions carry electric charge with respect to one of the U(1) factors and magnetic charge with respect to the other. The solutions describe stable zero temperature ground states of the deformed SCFT which have finite entropy density. We also construct analogous supersymmetric solutions that flow to $AdS_2\times S^2$ and to $AdS_2\times H^2/Γ$ in the IR which, in addition, carry magnetic R-symmetry charge similar to other known wrapped brane solutions.

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arXiv2012

Universal linear in temperature resistivity from black hole superradiance

Observations across many families of unconventional materials motivative the search for robust mechanisms producing linear in temperature d.c. resistivity. BKT quantum phase transitions are commonplace in holographic descriptions of finite density matter, separating critical and ordered phases. We show that at a holographic BKT critical point, if the unstable operator is coupled to the current via irrelevant operators, then a linear contribution to the resistivity is universally obtained. We also obtain broad power law tails in the optical conductivity, that shift spectral weight from the Drude peak as well as interband energy scales. We give a partial realization of this scenario using an Einstein-Maxwell-pseudoscalar bulk theory. The instability is a vectorial mode at nonzero wavevector, which is communicated to the homogeneous current via irrelevant coupling to an ionic lattice.

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arXiv2012

Helical superconducting black holes

We construct novel static, asymptotically $AdS_5$ black hole solutions with Bianchi VII$_0$ symmetry that are holographically dual to superconducting phases in four spacetime dimensions with a helical p-wave order. We calculate the precise temperature dependence of the pitch of the helical order. At zero temperature the black holes have vanishing entropy and approach domain wall solutions that reveal homogenous, non-isotropic dual ground states with emergent scaling symmetry.

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arXiv2012

Black holes dual to helical current phases

We consider the class of d=4 CFTs at finite temperature and chemical potential that are holographically described within D=5 Einstein-Maxwell theory with a Chern-Simons term. The high temperature phase, which is spatially homogeneous and isotropic, is dual to the AdS-Reissner-Nordstrom black brane solution. For sufficiently large Chern-Simons coupling, we construct new electrically charged AdS black hole solutions that are dual to the low temperature, spatially modulated phase. In this phase the current, associated with the abelian global symmetry, spontaneously acquires a helical order. The new black holes are stationary and also have Bianchi VII$_0$ symmetry.

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arXiv2012

Magnetic and electric AdS solutions in string- and M-theory

The stability properties of a family of magnetic $AdS_{3}\times \mathbb{R}^{2}$ solutions of D=5, SO(6) gauged SUGRA are investigated in more detail. We construct an analogous family of magnetic $AdS_{2}\times \mathbb{R}^{2}$ solutions of D=4, SO(8) gauged SUGRA, including a family of supersymmetric solutions, and also investigate their stability. We construct supersymmetric domain walls that interpolate between AdS_5 and an $AdS_3\times\mathbb{R}^2$ solution and also between AdS_4 and an $AdS_2\times\mathbb{R}^2$ solution which provide stable zero temperature ground states for the corresponding dual CFTs. We also construct new families of electric $AdS_{2}\times \mathbb{R}^{3}$ and $AdS_{2}\times \mathbb{R}^{2}$ solutions.

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arXiv2012

Spatially modulated instabilities of magnetic black branes

We investigate spatially modulated instabilities of magnetically charged $AdS_{2}\times\mathbb{R}^2$, $AdS_{3}\times\mathbb{R}^2$ and $AdS_{2}\times\mathbb{R}^3$ backgrounds in a broad class of theories, including those arising from KK reductions of ten and eleven dimensional supergravity. We show that magnetically charged black brane solutions in D=4,5 spacetime dimensions, whose zero temperature near horizon limit approach these backgrounds, can have instabilities that are dual to phases with current density waves that spontaneously break translation symmetry. Our examples include spatially modulated instabilities for a new class of magnetic black brane solutions of D=5 SO(6) gauged supergravity, that we construct in closed form, which are dual to new phases of N=4 SYM theory.

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arXiv2011

Holographic helical superconductors

We show that D=5 electrically charged AdS black branes can have instabilities associated with spatially modulated p-wave superconductors with helical structure. We show that the instabilities are present within N=4 $SU(2)\times U(1)$ gauged supergravity and hence within D=10 and D=11 supergravity.

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arXiv2011

Holographic striped phases

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 $AdS_4\times SE_7$ solutions of D=11 supergravity, albeit at a lower temperature than the known superfluid instabilities.

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