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Bom Soo Kim

Publications and source records attributed to Bom Soo Kim.

35 records · Page 2Linked to original sources
arXiv2013

Bulk Viscosity in Holographic Lifshitz Hydrodynamics

We compute the bulk viscosity in holographic models dual to theories with Lifshitz scaling and/or hyperscaling violation, using a generalization of the bulk viscosity formula derived in arXiv:1103.1657 from the null focusing equation. We find that only a class of models with massive vector fields are truly Lifshitz scale invariant, and have a vanishing bulk viscosity. For other holographic models with scalars and/or massless vector fields we find a universal formula in terms of the dynamical exponent and the hyperscaling violation exponent.

hep-th↗
arXiv2013

Aging Logarithmic Galilean Field Theories

We analytically compute correlation and response functions of scalar operators for the systems with Galilean and corresponding aging symmetries for general spatial dimensions $d$ and dynamical exponent $z$, along with their logarithmic and logarithmic squared extensions, using the gauge/gravity duality. These non-conformal extensions of the aging geometry are marked by two dimensionful parameters, eigenvalue $\mathcal M$ of an internal coordinate and aging parameter $α$. We further perform systematic investigations on two-time response functions for general $d$ and $z$, and identify the growth exponent as a function of the scaling dimensions $Δ$ of the dual field theory operators and aging parameter $α$ in our theory. The initial growth exponent is only controlled by $Δ$, while its late time behavior by $α$ as well as $Δ$. These behaviors are separated by a time scale order of the waiting time. We attempt to make contact our results with some field theoretical growth models, such as Kim-Kosterlitz model at higher number of spatial dimensions $d$.

hep-th↗
arXiv2012

Hyperscaling violation : a unified frame for effective holographic theories

We investigate systematic classifications of low energy and lower dimensional effective holographic theories with Lifshitz and Schrödinger scaling symmetries only using metrics in terms of hyperscaling violation ($θ$) and dynamical ($z$) exponents. Their consistent parameter spaces are constrained by null energy and positive specific heat conditions, whose validity is explicitly checked against a previously known result. From dimensional reductions of many microscopic string solutions, we observe the classifications are tied with the number of scales in the original microscopic theories. Conformal theories do not generate a nontrivial $θ$ for a simple sphere reduction. Theories with Lifshitz scaling with one scale are completely fixed by $θ$ and $z$, and have a universal emblackening factor at finite temperature. Dimensional reduction of intersecting M2-M5 requires, we call, spatial anisotropic exponents ($\sharp$), along with $z$=1, $θ$=0, because of another scale. Theories with Schrödinger scaling show similar simple classifications at zero temperature, while require more care due to an additional parameter being a thermodynamic variable at finite temperature.

hep-th↗
arXiv2012

Aging Logarithmic Conformal Field Theory : a holographic view

We consider logarithmic extensions of the correlation and response functions of scalar operators for the systems with aging as well as Schrödinger symmetry. Aging is known to be the simplest nonequilibrium phenomena, and its physical significances can be understood by the two-time correlation and response functions. Their logarithmic part is completely fixed by the bulk geometry in terms of the conformal weight of the dual operator and the dual particle number. Motivated by recent experimental realizations of Kardar-Parisi-Zhang universality class in growth phenomena and its subsequent theoretical extension to aging, we investigate our two-time correlation functions out of equilibrium, which show several qualitatively different behaviors depending on the parameters in our theory. They exhibit either growing or aging, i.e. power-law decaying, behaviors for the entire range of our scaling time. Surprisingly, for some parameter ranges, they exhibit growing at early times as well as aging at later times.

hep-th↗
arXiv2012

Schrödinger Holography with and without Hyperscaling Violation

We study the properties of the Schrödinger-type non-relativistic holography for general dynamical exponent z with and without hyperscaling violation exponent θ. The scalar correlation function has a more general form due to general z as well as the presence of θ, whose effects also modify the scaling dimension of the scalar operator. We propose a prescription for minimal surfaces of this "codimension 2 holography," and demonstrate the (d-1) dimensional area law for the entanglement entropy from (d+3) dimensional Schrödinger backgrounds. Surprisingly, the area law is violated for d+1 < z < d+2, even without hyperscaling violation, which interpolates between the logarithmic violation and extensive volume dependence of entanglement entropy. Similar violations are also found in the presence of the hyperscaling violation. Their dual field theories are expected to have novel phases for the parameter range, including Fermi surface. We also analyze string theory embeddings using non-relativistic branes.

hep-th↗
arXiv2012

Finite Temperature Aging Holography

We construct the gravity background which describes the dual field theory with aging invariance. We choose the decay modes of the bulk scalar field in the internal spectator direction to obtain the dissipative behavior of the boundary correlation functions of the dual scalar fields. In particular, the two-time correlation function at zero temperature has the characteristic features of the aging system: power law decay, broken time translation and dynamical scaling. We also construct the black hole backgrounds with asymptotic aging invariance. We extensively study characteristic behavior of the finite temperature two-point correlation function via analytic and numerical methods.

hep-th↗
arXiv2012

Holographic quantum criticality and strange metal transport

A holographic model of a quantum critical theory at a finite but low temperature, and finite density is studied. The model exhibits non-relativistic z=2 Schrödinger symmetry and is realized by the Anti-de-Sitter-Schwarzschild black hole in light-cone coordinates. Our approach addresses the electrical conductivities in the presence or absence of an applied magnetic field and contains a control parameter that can be associated to quantum tuning via charge carrier doping or an external field in correlated electron systems. The Ohmic resistivity, the inverse Hall angle, the Hall coefficient and the magnetoresistance are shown to be in good agreement with experimental results of strange metals at very low temperature. The holographic model also predicts new scaling relations in the presence of a magnetic field.

cond-mat.str-el↗
arXiv2011

Properties of Schroedinger Black Holes from AdS Space

Properties of Schroedinger black holes are derived from AdS black holes expressed in light-cone coordinates with a particular normalization. The advantages of this method over the direct analysis of the Schroedinger geometry are the simplicity and the well-defined Brown-York procedure with the standard counterterms. The method is demonstrated for several physical interests, including the computation of the DC conductivity and the derivation of the R-charged black hole thermodynamic properties.

hep-th↗
arXiv2011

Charged Dilatonic Black Holes and their Transport Properties

We briefly explain the consistency conditions imposed on the effective holographic theories, which are parameterized by two real exponents $(γ,δ)$ that control the IR dynamics. The general scaling of DC resistivity with temperature at low temperature and AC conductivity at low frequency across the whole $(γ,δ)$ plane are explained. There is a codimension-one region where the DC resistivity is linear in the temperature. For massive carriers, it is shown that when the scalar operator is not the dilaton, the DC resistivity scales as the heat capacity (and entropy) for $(2+1)$-dimensional systems. Regions are identified where the theory at finite density is a Mott-like insulator. This contribution is based on arXiv:1005.4690 with emphasis on the transport properties of charged dilatonic black holes with potential.

hep-th↗
arXiv2011

Strange Metallic Behaviour and the Thermodynamics of Charged Dilatonic Black Holes

We review a recent holographic analysis arXiv:1005.4690 of charged black holes with scalar hair in view of their applications to the cuprate high temperature superconductors. We show in particular that these black holes show an interesting phase structure including critical behaviour at zero temperature or charge, describe both conductors and insulators (including holographic Mott-like insulators), generically have no residual entropy and exhibit experimentally observed scaling relations between electronic entropy, specific heat and (linear) DC resistivity. Transport properties are discussed in the companion contribution to these proceedings.

hep-th↗
arXiv2008

Bosonization of Matter $βγ$ CFT, Non-compact Coordinate and Noncritical String Theory

We consider a (supersymmetric) bosonization of general commuting matter $βγ$ CFT. Unlike the conventional ghost $βγ$ CFT bosonization, which is typically described in terms of one scalar and one set of $ξη$ CFT, the matter $βγ$ CFT is naturally bosonized to two scalar CFTs. Surprisingly, there exists an independent subsector, which satisfies a constraint necessary for consistent bosonization, while the usual sector has a description in terms of two compact coordinates. The subsector itself is a complete system which is equivalent to the original $βγ$ CFT. Furthermore, a non-compact coordinate naturally emerges in this "non-compact subsector". As an immediate application, we consider the bosonization of matter $βγ$ CFT in the context of full string theory and find the connection to noncritical string theories in the light-cone gauge.

hep-th↗
arXiv2007

Non-Relativistic Superstring Theories

We construct a supersymmetric version of the ``critical'' non-relativistic bosonic string theory\cite{Kim:2007hb} with its manifest global symmetry. We introduce the anticommuting $bc$ CFT which is the super partner of the $βγ$ CFT. The conformal weights of the $b$ and $c$ fields are both 1/2. The action of the fermionic sector can be transformed into that of the relativistic superstring theory. We explicitly quantize the theory with manifest SO(8) symmetry and find that the spectrum is similar to that of Type IIB superstring theory. There is one notable difference: the fermions are non-chiral. We further consider ``noncritical'' generalizations of the supersymmetric theory using the superspace formulation. There is an infinite range of possible string theories similar to the supercritical string theories. We comment on the connection between the critical non-relativistic string theory and the lightlike Linear Dilaton theory.

hep-th↗
arXiv2007

World Sheet Commuting βγCFT and Non-Relativistic String Theories

We construct a sigma model in two dimensions with Galilean symmetry in flat target space similar to the sigma model of the critical string theory with Lorentz symmetry in 10 flat spacetime dimensions. This is motivated by the works of Gomis and Ooguri\cite{Gomis:2000bd} and Danielsson et. al. \cite{Danielsson:2000gi, Danielsson:2000mu}. Our theory is much simpler than their theory and does not assume a compact coordinate. This non-relativistic string theory has a bosonic matter $βγ$ CFT with the conformal weight of $β$ as 1. It is natural to identify time as a linear combination of $γ$ and $\barγ$ through an explicit realization of the Galilean boost symmetry. The angle between $γ$ and $\barγ$ parametrizes one parameter family of selection sectors. These selection sectors are responsible for having a non-relativistic dispersion relation without a nontrivial topology in the non-relativistic setup, which is one of the major differences from the previous works\cite{Gomis:2000bd, Danielsson:2000gi, Danielsson:2000mu}. This simple theory is the non-relativistic analogue of the critical string theory, and there are many different avenues ahead to be investigated. We mention a possible consistent generalization of this theory with different conformal weights for the $βγ$ CFT. We also mention supersymmetric generalizations of these theories.

hep-th↗
arXiv2007

Aspects of Puff Field Theory

We describe some features of the recently constructed "Puff Field Theory," and present arguments in favor of it being a field theory decoupled from gravity. We construct its supergravity dual and calculate the entropy of this theory in the limit of large 't Hooft coupling. We also determine the leading irrelevant operator that governs its deviation from N=4 super Yang-Mills theory.

hep-th↗
arXiv2005

A Deformation of Twistor Space and a Chiral Mass Term in N=4 Super Yang-Mills Theory

Super twistor space admits a certain (super) complex structure deformation that preserves the Poincare subgroup of the symmetry group PSL(4|4) and depends on 10 parameters. In a previous paper [hep-th/0502076], it was proposed that in twistor string theory this deformation corresponds to augmenting N=4 super Yang-Mills theory by a mass term for the left-chirality spinors. In this paper we analyze this proposal in more detail. We calculate 4-particle scattering amplitudes of fermions, gluons and scalars and show that they are supported on holomorphic curves in the deformed twistor space.

hep-th↗
arXiv2005

Massless and Massive Three Dimensional Super Yang-Mills Theory and Mini-Twistor String Theory

We propose various ways of adding mass terms to three-dimensional twistor string theory. We begin with a review of mini-twistor space--the reduction of D=4 twistor space to D=3. We adapt the two proposals for twistor string theory, Witten's and Berkovits's, to D=3 super Yang-Mills theory. In Berkovits's model, we identify the enhanced R-symmetry. We then construct B-model topological string theories that, we propose, correspond to D=3 Yang-Mills theory with massive spinors and massive and massless scalars in the adjoint representation of the gauge group. We also analyze the counterparts of these constructions in Berkovits's model. Some of our constructions can be lifted to D=4, where infinitesimal mass terms correspond to VEVs of certain superconformal gravity fields.

hep-th↗