arXiv subjects

Mike Blake

Publications and source records attributed to Mike Blake.

26 records · Page 2Linked to original sources

arXiv2015

Magnetothermoelectric Response from Holography

In this note we study the effects of a magnetic field on transport using holographic models with broken translational invariance. We show that, after carefully subtracting off non-trivial magnetisation currents, it is possible to express the DC transport currents of the boundary theory in terms of properties of a black hole horizon. This allows us to obtain simple analytic expressions for the electrical, thermoelectric and heat conductivity tensors. Our results apply to both isotropic and anisotropic models, including holographic Q-lattices and to certain theories where translational invariance is broken by linear sources for axions.

hep-th↗

arXiv2015

Magnetotransport from the fluid/gravity correspondence

We continue our construction of a hydrodynamical description of a holographic model with broken translation invariance. Using the fluid/gravity correspondence we derive the constitutive relations of the boundary theory in the presence of a magnetic field. This allows us to obtain novel results for the low-frequency magnetothermoelectric response coefficients. We discuss the DC limit of our hydrodynamics in detail, and show that our approach is equivalent to the `horizon-fluid' of Donos and Gauntlett.

hep-th↗

arXiv2015

Quantum Critical Transport and the Hall Angle

In this letter we study the Hall conductivity in holographic models where translational invariance is broken by a lattice. We show that generic holographic theories will display a different temperature dependence in the Hall angle as to the DC conductivity. Our results suggest a general mechanism for obtaining an anomalous scaling of the Hall angle in strongly interacting quantum critical systems.

hep-th↗

arXiv2014

Holographic Charge Oscillations

The Reissner-Nordstrom black hole provides the prototypical description of a holographic system at finite density. We study the response of this system to the presence of a local, charged impurity. Below a critical temperature, the induced charge density, which screens the impurity, exhibits oscillations. These oscillations can be traced to the singularities in the density-density correlation function moving in the complex momentum plane. At finite temperature, the oscillations are very similar to the Friedel oscillations seen in Fermi liquids. However, at zero temperature the oscillations in the black hole background remain exponentially damped, while Friedel oscillations relax to a power-law

hep-th↗

arXiv2014

Holographic Lattices Give the Graviton a Mass

We discuss the DC conductivity of holographic theories with translational invariance broken by a background lattice. We show that the presence of the lattice induces an effective mass for the graviton via a gravitational version of the Higgs mechanism. This allows us to obtain, at leading order in the lattice strength, an analytic expression for the DC conductivity in terms of the size of the lattice at the horizon. In locally critical theories this leads to a power law resistivity that is in agreement with an earlier field theory analysis of Hartnoll and Hofman.

hep-th↗

arXiv2013

Universal Resistivity from Holographic Massive Gravity

Massive gravity provides a holographic model for theories exhibiting momentum dissipation. We provide an analytic expression for the DC conductivity. The result is universal, depending only on properties of the infra-red horizon, and holds at finite temperature and charge density. In addition, we provide a derivation of black hole thermodynamics in holographic massive gravity and show that the resulting physics is sensible.

hep-th↗

arXiv2012

Large Nc Equivalence and Baryons

In the large Nc limit, gauge theories with different gauge groups and matter content sometimes turn out to be `large Nc equivalent', in the sense of having a set of coincident correlation functions. Large Nc equivalence has mainly been explored in the glueball and meson sectors. However, a recent proposal to dodge the fermion sign problem of QCD with a quark-number chemical potential using large Nc equivalence motivates investigating the applicability of large Nc equivalence to correlation functions involving baryon operators. Here we present evidence that large Nc equivalence extends to the baryon sector, under the same type of symmetry-realization assumptions as in the meson sector, by adapting the classic Witten analysis of large Nc baryons.

hep-th↗

arXiv2012

Holographic Dual of the Lowest Landau Level

We describe the lowest Landau level of a quantum electron star in AdS4. In the presence of a suitably strong magnetic field, the dynamics of fermions in the bulk is effectively reduced from four to two dimensions. These two-dimensional fermions can subsequently be treated using the techniques of bosonization and the difficult many-body problem of building a gravitating, charged quantum star is reduced to solving the sine-Gordon model coupled to a gauge field and a metric. The kinks of the sine-Gordon model provide the holographic dual of the lowest Landau levels of the strongly-coupled d=2+1 dimensional boundary field theory. The system exhibits order one oscillations in the magnetic susceptibility, now arising as a classical effect in the bulk. Moreover, as the chemical potential is varied, we find jumps in the charge density, oscillations in the fractionalised charge density and plateaux in the cohesive charge density

hep-th↗