arXiv subjects

Sang-Jin Sin

Publications and source records attributed to Sang-Jin Sin.

At least 109 records · Page 6Linked to original sources

arXiv2010

Magnetic conductivity and Chern-Simons Term in Holographic Hydrodynamics of Charged AdS Black Hole

We study the effects of the Chern-Simons term in the hydrodynamics of the five-dimensional Reissner-Nordstrom-AdS background. We work out the decoupling problem of the equations of motion and calculate the retarded Green functions explicitly. We then find that the Chern-Simons term induces the magnetic conductivity caused by the anomaly effect. It is increasing function of temperature running from a non-zero value at zero temperature to the twice the value at infinite temperature.

hep-th↗

arXiv2010

Acoustic black holes for relativistic fluids

We derive a new acoustic black hole metric from the Abelian Higgs model. In the non-relativistic limit, while the Abelian Higgs model becomes the Ginzburg-Landau model, the metric reduces to an ordinary Unruh type. We investigate the possibility of using (type I and II) superconductors as the acoustic black holes. We propose to realize experimental acoustic black holes by using spiral vortices solutions from the Navier-stokes equation in the non-relativistic classical fluids.

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arXiv2009

Holographic Hadrons in a Confining Finite Density Medium

We study a sector of the hadron spectrum in the presence of finite baryon density. We use a non-supersymmetric gravity dual to a confining guage theory which exhibits a running dilaton. The interaction of mesons with the finite density medium is encoded in the dual theory by a force balancing between flavor D7-branes and a baryon vertex provided by a wrapped D5-brane. When the current quark mass m_q is sufficiently large, the meson mass reduces, exhibiting an interesting spectral flow as we increase the baryon density while it has a more complicated behaviour for very small m_q.

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arXiv2009

Density driven symmetry breaking and Butterfly effect in holographic superconductors

We study the density driven symmetry breaking in holographic superconductors by considering the positive mass squared case. We show that even for the positive $m^2$, a scalar condensation still forms, provided the chemical potential is high enough. As $m^2$ increases, the phase space folds due to the non-linearity of the equations of motion, and two nearby points in the phase space can represent symmetry breaking and preserving configurations respectively. The phase space defined by the set of initial conditions of field variables at the horizon undergoes a non-linear radial evolution to result in the phase space folding, a characteristic phenomenon in a non-linear system. We then calculate the specific heat, which characterizes superconductors and has been measured in experiments.We observe a discontinuity in the specific heat at the transition point and compare our results with experimentally observed numbers. The electrical conductivity for various $m^2$ is also calculated.

hep-th↗

arXiv2009

Nuclear matter to strange matter transition in holographic QCD

We construct a simple holographic QCD model to study nuclear matter to strange matter transition. The interaction of dense medium and hadrons is taken care of by imposing the force balancing condition for stable D4/D6/D6 configuration. By considering the intermediate and light flavor branes interacting with baryon vertex homogeneously distributed along R^3 space and requesting the energy minimization, we find that there is a well defined transition density as a function of current quark mass. We also find that as density goes up very high, intermediate (or heavy) and light quarks populate equally as expected from the Pauli principle. In this sense, the effect of the Pauli principle is realized as dynamics of D-branes.

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arXiv2009

Holographic dual of Cold Trapped Fermions

We study cold fermionic atoms using the holographic principle. We note that current atomic experiments with massive fermions trapped in a harmonic potential in the unitarity limit behave as massless fermions thanks to the Thomas-Fermi approximation. We map the thermodynamics of strongly correlated massless fermion to that of the charged black hole and study the thermodynamics and transport properties of cold fermions at strong coupling at finite temperature and density. In cold limit, the specific heat of charged black hole is linear in $T$ independent of the dimensionality, which is reminiscent of Fermi liquids. The shear viscosity per particle is shown to be finite as a consequence of the non-vanishing of the entropy. We show that our holographic results compare favorably with most of the current atomic data.

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arXiv2009

The effect of gluon condensate on holographic heavy quark potential

The gluon condensate is very sensitive to the QCD deconfinement transition since its value changes drastically with the deconfinement transition. We calculate the gluon condensate dependence of the heavy quark potential in AdS/CFT to study how the property of the heavy quarkonium is affected by a relic of the deconfinement transition. We observe that the heavy quark potential becomes deeper as the value of the gluon condensate decreases. We interpret this as a dropping of the heavy quarkonium mass just above the deconfinement transition, which is similar to the results obtained from QCD sum rule and from a bottom-up AdS/QCD model.

hep-th↗

arXiv2009

Holographic melting of Heavy Baryons in Plasma with Gluon Condensation

We propose a Dirac-Born-Infeld (DBI) D5 vertex brane plus N_c fundamental strings configuration to describe a baryon probe in strongly coupled gauge theory with gluon condensation at finite temperature via AdS/CFT correspondence. We investigate properties of this configuration in a dilaton deformed AdS_5\times S^5 background, in which IIB string theroy is dual to super Yang-Mills thery in a state with a constant self-dual gauge field (F_{mn}=F^*_{mn}) background. We find that for most values of temperature T and gluon condensation parameter q (q = π^2 ), there always exists a screening length L_s. The relation L_s\sim{1\ov T} has been checked. We give the q dependence of L_s. We calculate the boost velocity v(v=-\tanhη) and angular velocity ωdependence of L_s for a baryon probe, and obtain L_s=L_0*(1-v^2)^{1/4} for large v and L_s\simω^{-1}, which are consistent with those dependence relations in the point brane plus strings case, and find that the usual relations have been modified by q. We also calculate the mass of baryon and find T dependence of baryon mass.

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arXiv2009

Comments on Baryon Melting in Quark Gluon Plasma with Gluon Condensation

We consider a black hole solution with a non-trivial dilaton from IIB super gravity which is expected to describe a strongly coupled hot gauge plasma with non-vanishing gluon condensation present. We construct a rotating and moving baryon to probe the screening and phases of the plasma. Melting of the baryons in hot plasma in this background had been studied previously, however, we show that baryons melt much lower temperature than has been suggested previously.

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arXiv2009

A Holographic model for Non-Relativistic Superconductor

We build a holographic description of non-relativistic system for superconductivity in strongly interacting condensed matter via gauge/gravity duality. We focus on the phase transition and give an example to show that a simple gravitational theory can provide a non-relativistic holographical dual description of a superconductor. There is also a critical temperature like the relativistic case, below which a charged condensation field appears by a second order phase transition and the (DC) conductivity becomes infinite. We also calculated the frequency dependent conductivity.

hep-th↗

arXiv2009

Dense QCD: a Holographic Dyonic Salt

Dense QCD at zero temperature with a large number of colors is a crystal. We show that in the holographic dual description, the crystal is made out of pairs of dyons with $e=g=\pm 1$ charges in a salt-like arrangement. We argue that with increasing density the dyon masses and topological charges equalize, turning the salt-like configuration to a bcc of half-instantons. The latter is dual to a cubic crystal of half-skyrmions. We estimate the transition from an fcc crystal of instantons to a bcc crystal of dyons to about 3 times nuclear matter density with a dyon binding energy of about 180 MeV.

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arXiv2009

Holographic QCD in medium: a bottom up approach

A holographic dual of hadrons at finite density is considered. We use the zero black-hole mass limit of Reisner-Nordstrom (RN) AdS background with hard wall to describe a confining background with finite quark density. We calculate density-dependence of meson masses and decay constants. In our model, pion decay constant and its velocity go down but all the meson masses go up as density grows.

hep-ph↗

arXiv2009

Shear viscosity and instability from third order Lovelock gravity

We calculate the ratio of shear viscosity to entropy density for charged black branes in third order Lovelock theory. For chargeless black branes, the result turns out to be consistent with the prediction made in $\rm arXiv:0808.3498[\rm hep-th] $. We find that, the third order Lovelock gravity term does not contribute to causality violation unlike the Gauss-Bonnet term. The stability of the black brane again requires the value of the Lovelock coupling constant to be bounded by 1/4 in the infinite dimensionality limit.

hep-th↗

arXiv2009

A Dual Geometry of the Hadron in Dense Matter

We identify the dual geometry of the hadron phase of dense nuclear matter and investigate the confinement/deconfinement phase transition. We suggest that the low temperature phase of the RN black hole with the full backreaction of the bulk gauge field is described by the zero mass limit of the RN black hole with hard wall. We calculated the density dependence of critical temperature and found that the phase diagram closes. We also study the density dependence of the rho meson mass.

hep-th↗

arXiv2009

Shear viscosity, instability and the upper bound of the Gauss-Bonnet coupling constant

We compute the dimensionality dependence of $η/s$ for charged black branes with Gauss-Bonnet correction. We find that both causality and stability constrain the value of Gauss-Bonnet coupling constant to be bounded by 1/4 in the infinite dimensionality limit. We further show that higher dimensionality stabilize the gravitational perturbation. The stabilization of the perturbation in higher dimensional space-time is a straightforward consequence of the Gauss-Bonnet coupling constant bound.

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arXiv2009

Sound Modes in Holographic Hydrodynamics for Charged AdS Black Hole

In the previous paper we studied the transport coefficients of Quark-Gluon Plasma in finite temperature and finite density in vector and tensor modes. In this paper, we extend it to the scalar modes. We work out the decoupling problem and hydrodynamic analysis for the sound mode in charged AdS black hole and calculate the sound velocity, the charge susceptibility and the electrical conductivity. We find that Einstein relation among the conductivity, the diffusion constant and the susceptibility holds exactly.

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arXiv2008

Hydrodynamics with conserved current from the gravity dual

We determine the structure of the hydrodynamics with conserved current, using the gauge/gravity duality of charged black-hole background. It turns out that even in the presence of the external electromagnetic field at the boundary, bulk Einstein equation is equivalent to the boundary conservation of energy momentum tensor and that of current. As a consequence, the thermal conductivity and electric conductivity are calculated in terms of the parameters of the fundamental theory. We find that Wiedermann-Franz law hold with Lorentz number $1/e^2$

hep-th↗

arXiv2008

Viscosity Bound, Causality Violation and Instability with Stringy Correction and Charge

Recently, it has been shown that if we consider the higher derivative correction, the viscosity bound conjectured to be $η/s=1/4π$ is violated and so is the causality. In this paper, we consider medium effect and the higher derivative correction simultaneously by adding charge and Gauss-Bonnet terms. We find that the viscosity bound violation is not changed by the charge. However, we find that two effects together create another instability for large momentum regime. We argue the presence of tachyonic modes and show it numerically. The stability of the black brane requires the Gauss-Bonnet coupling constant $λ$($=2α'/l^2$) to be smaller than 1/24. We draw a phase diagram relevant to the instability in charge-coupling space.

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