arXiv subjects

Jae-Hyuk Oh

Publications and source records attributed to Jae-Hyuk Oh.

27 records · Page 2Linked to original sources

arXiv2013

Transport in non-conformal holographic fluids

We have considered non-conformal fluid dynamics whose gravity dual is a certain Einstein dilaton system with Liouville type dilaton potential, characterized by an intrinsic parameter $η$. We have discussed the Hawking-Page transition in this framework using hard-wall model and it turns out that the critical temperature of the Hawking-Page transition encapsulates a non-trivial dependence on $η$. We also obtained transport coefficients such as AC conductivity, shear viscosity and diffusion constant in the hydrodynamic limit, which show non-trivial $η$ dependent deviations from those in conformal fluids, although the ratio of the shear viscosity to entropy density is found to saturate the universal bound. Some of the retarded correlators are also computed in the high frequency limit for case study.

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arXiv2012

Stochastic quantization and holographic Wilsonian renormalization group

We study relation between stochastic quantization and holographic Wilsonian renormalization group flow. Considering stochastic quantization of the boundary on-shell actions with the Dirichlet boundary condition for certain $AdS$ bulk gravity theories, we find that the radial flows of double trace deformations in the boundary effective actions are completely captured by stochastic time evolution with identification of the $AdS$ radial coordinate `$r$' with the stochastic time '$t$' as $r=t$. More precisely, we investigate Langevin dynamics and find an exact relation between radial flow of the double trace couplings and 2-point correlation functions in stochastic quantization. We also show that the radial evolution of double trace deformations in the boundary effective action and the stochastic time evolution of the Fokker-Planck action are the same. We demonstrate this relation with a couple of examples: (minimally coupled)massless scalar fields in $AdS_2$ and U(1) vector fields in $AdS_4$.

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arXiv2012

Boundary conditions for SU(2) Yang-Mills on $AdS_4$

We consider SU(2) Yang-Mills theory on $AdS_4$ by imposing various boundary conditions, which correspond to non-trivial deformations of its boundary $CFT$. We obtain classical solutions of Yang-Mills fields up to the first subleading order correction by using small amplitude expansion of the gauge field without considering gravitational back reaction. We also consider SU(2) Yang-Mills instanton solution in $AdS_4$ bulk, and propose a boundary action. It turns out that the boundary theory is the Chern Simons theory with a non-local deformation which has the form similar to the Wilson line. In the limit of the deformation parameter $ρ\rightarrow \infty$, this non-local deformation is suppressed and the boundary theory becomes pure Chern Simons. For large but finite values of $ρ$, this non-local deformation can be treated perturbatively within the Chern-Simon theory.

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arXiv2012

Running Shear Viscosities in Anisotropic Holographic Superfluids

We have examined holographic renormalization group($RG$) flows of the shear viscosities in anisotropic holographic superfluids via their gravity duals, Einstein-SU(2) Yang-Mills system. In anisotropic phase, below the critical temperature $T_c$, the SO(3) isometry(spatial rotation) in the dual gravity system is broken down to the residual SO(2). The shear viscosities in the symmetry broken directions of the conformal fluids defined on $AdS$ boundary present non-universal values which depend on the chemical potential $μ$ and temperature $T$ of the system and also satisfy non-trivial holographic $RG$-flow equations. The shear viscosities flow down to the specific values in $IR$ region, in fact which are given by the ratios of the metric components in the symmetry unbroken direction to those in the broken directions, evaluated at the black brane horizon in the dual gravity system.

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arXiv2012

Analytic Approaches to anisotropic Holographic Superfluids

We construct an analytic solution of the Einstein-SU(2)-Yang-Mills system as the holographic dual of an anisotropic superfluid near its critical point, up to leading corrections in both the inverse Yang-Mills coupling and a symmetry breaking order parameter. We have also calculated the ratio of shear viscosity to entropy density in this background, and shown that the universality of this ratio is lost in the broken symmetry direction. The ratio displays a scaling behavior near the critical point with critical exponent $β=1$, at the leading order in the double expansion.

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arXiv2011

Annulus amplitude of FZZT branes revisited

We revisit the annulus amplitude of FZZT branes with general matter sectors (r,s) using the recent development of matrix model and minimal Liouville gravity. Following the boundary description of the 1-matrix model and bulk resonance transformation between primary operators we find the consistency of the brane decomposition into (1,1)-branes. We also investigate the corresponding results obtained directly from the minimal Liouville gravity and demonstrate the perfect agreement with the matrix results.

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arXiv2011

On Dumb Holes and their Gravity Duals

Inhomogeneous fluid flows which become supersonic are known to produce acoustic analogs of ergoregions and horizons. This leads to Hawking-like radiation of phonons with a temperature essentially given by the gradient of the velocity at the horizon. We find such acoustic dumb holes in charged conformal fluids and use the fluid-gravity correspondence to construct dual gravity solutions. A class of quasinormal modes around these gravitational backgrounds perceive a horizon. Upon quantization, this implies a thermal spectrum for these modes.

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arXiv2011

Small Amplitude Forced Fluid Dynamics from Gravity at T = 0

The usual derivative expansion of gravity duals of charged fluid dynamics is known to break down in the zero temperature limit. In this case, the fluid-gravity duality is not understood precisely. We explore this problem for a zero temperature charged fluid driven by a low frequency, small amplitude and spatially homogeneous external force. In the gravity dual, this corresponds to time dependent boundary value of the dilaton. We calculate the bulk solution for the dilaton and the leading backreaction to the metric and the gauge fields using the modified low frequency expansion of [11]. The resulting solutions are regular everywhere, establishing fluid-gravity duality to this order.

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arXiv2009

Slowly Varying Dilaton Cosmologies and their Field Theory Duals

We consider a deformation of the $AdS_5\times S^5$ solution of IIB supergravity obtained by taking the boundary value of the dilaton to be time dependent. The time dependence is taken to be slowly varying on the AdS scale thereby introducing a small parameter $ε$. The boundary dilaton has a profile which asymptotes to a constant in the far past and future and attains a minimum value at intermediate times. We construct the sugra solution to first non-trivial order in $ε$, and find that it is smooth, horizon free, and asymptotically $AdS_5\times S^5$ in the far future. When the intermediate values of the dilaton becomes small enough the curvature becomes of order the string scale and the sugra approximation breaks down. The resulting dynamics is analysed in the dual SU(N) gauge theory on $S^3$ with a time dependent coupling constant which varies slowly. When $N ε\ll 1$, we find that a quantum adiabatic approximation is applicable, and use it to argue that at late times the geometry becomes smooth $AdS_5\times S^5$ again. When $N ε\gg 1$, we formulate a classical adiabatic perturbation theory based on coherent states which arises in the large $N$ limit. For large values of the 'tHooft coupling this reproduces the supergravity results. For small 'tHooft coupling the coherent state calculations become involved and we cannot reach a definite conclusion. We argue that the final state should have a dual description which is mostly smooth $AdS_5$ space with the possible presence of a small black hole.

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