arXiv subjects

Chanyong Park

Publications and source records attributed to Chanyong Park.

105 records · Page 6Linked to original sources

arXiv2007

Deconfinement phase transition in holographic QCD with matter

In the framework of a holographic QCD approach we study an influence of matters on the deconfinement temperature, $T_c$. We first consider quark flavor number ($N_f$) dependence of $T_c$. We observe that $T_c$ decreases with $N_f$, which is consistent with a lattice QCD result. We also delve into how the quark number density $ρ_q$ affects the value of $T_c$. We find that $T_c$ drops with increasing $ρ_q$. In both cases, we confirm that the contributions from quarks are suppressed by $1/N_c$, as it should be, compared to the ones from a gravitational action (pure Yang-Mills).

hep-ph↗

arXiv2007

Domain wall cosmology and multiple accelerations

We classify the cosmological behaviors of the domain wall under junctions between two spacetimes in terms of various parameters: cosmological constants of bulk spacetime, a tension of a domain wall, and mass parameters of the black hole-type metric. Especially, we consider the false-true vacuum type junctions and the domain wall connecting between an inner AdS space and an outer AdS Reissner-Nordstr${\rm \ddot{o}}$m black hole. We find that there exist a solution to the junction equations with an inflation at earlier times and an accelerating expansion at later times.

hep-th↗

arXiv2006

The false vacuum bubble nucleation due to a nonminimally coupled scalar field

We study the possibility of forming the false vacuum bubble nucleated within the true vacuum background via the true-to-false vacuum phase transition in curved spacetime. We consider a semiclassical Euclidean bubble in the Einstein theory of gravity with a nonminimally coupled scalar field. In this paper we present the numerical computations as well as the approximate analytical computations. We mention the evolution of the false vacuum bubble after nucleation.

hep-th↗

arXiv2005

More on supersymmetric D-branes in type IIB plane wave background

We extend the study on D-branes in the type IIB plane wave background to less supersymmetric configurations. We show that many new supersymmetric D-branes can be found by turning on electric as well as magnetic background fluxes, or constantly boosting D-branes.

hep-th↗

arXiv2005

Two Point Correlation Function of Sine-Liouville Theory

Exact two point correlation functions of sine-Liouville theory are presented for primary fields with U(1) charge neutral, which may either preserve or break winding number. Our result is checked with perturbative calculation and is also consistent with previous one which can be obtained by restricting the action parameters.

hep-th↗

arXiv2002

dS/CFT correspondence from the Brick Wall method

We research the entropy of a black hole in curved space-times by 't Hooft`s approach, so-called the brick wall method. One of these space-time, a asymptotically dS space-time has two physical horizons; one is a black hole horizon and the other is a cosmological horizon. The others have only one horizon, a black hole horizon. Using this model, we calculate all thermodynamic quantities containing the background geometric effect and show that entropy is proportional to area of each boundary. Furthermore, we show that the Cardy-Verlinde formula can be rederived from the physical quantities of the brick wall method and this fact becomes a evidence of the dS/CFT correspondence.

hep-th↗

arXiv2002

Radiative Correctionsin Noncommutative QED

We study the radiative corrections of the noncommutative QED at the one-loop level. A correction of the magnetic dipole moment due to the noncommutativity are evaluated. As in the ordinary QED, IR divergence is shown to vanish when we combine both the tree level Bremsstrahlung diagram and the one-loop electron vertex function.

hep-th↗

arXiv2000

Moving Domain Walls in $AdS_5$ and Graceful Exit from Inflation

We consider moving-brane-solutions in AdS type back ground. In the first Randall-Sundrum configuration, there are two branes at fixed points of the orbifold symmetry. We point out that if one brane is fixed and the other brane is moving, the configuration is still a solution provided the moving brane has a specific velocity determined by its tension and bulk cosmological constant. In the absence of the $\bf Z_2$ symmetry, we can construct multi-brane configurations by patching AdS-Schwarzshild solutions. In this case, we show that the 4-dimensional effective cosmological constant on the brane world is not well defined. We find a condition for a brane to be stationary. Using the brane scattering, we suggest a scenario of inflation on the brane universe during a finite time, i.e, a scenario of a graceful exit of inflation.

hep-th↗

arXiv1999

The cosmology with the Dp-brane gas

We study the effect of the Dp-brane gas in string cosmology. When one kind of Dp-brane gas dominates, we find that the cosmology is equivalent to that of the Brans-Dicke theory with the perfect fluid type matter. We obtain $γ$, the equation of state parameter, in terms of p and the space-time dimension.

hep-th↗

arXiv1999

Oscillating Inflation with a non-minimally coupled scalar field

The oscillating inflation model recently proposed by Damour and Mukhanov is investigated with a non-minimal coupling. Numerical study confirms an inflationary behavior and the density perturbation is obtained. A successful inflation requires the gravity-dilaton coupling to be small.

hep-th↗

arXiv1999

Phases of Brans-Dicke cosmology(II):Matter from NS-NS sector

We study the cosmology of the Brans-Dicke(BD) theory coupled to perfect fluid type matter. In our previous works, the case where matter is coming from the Ramond-Ramond sector of the string theory was studied. Here, we study the case where matter is coming from the NS-NS sector. Exact solutions are found and the cosmology is classified according to the values of $γ$, the parameter of the equation of state and $ω$, Brans-Dicke parameter. We find taht, in string frame, there are solutions without singularity for some ranges of $γ$ and $ω$. In Einstein frame, however, all solutions are singular.

gr-qc↗

arXiv1999

Phases of the Brans-Dicke Cosmology with Matter

We study the cosmology of the Brans-Dicke theory with perfect fluid type matter. In our previous work, we found exact solutions for any Brans-Dicke parameter $ω$ and for general parameter $γ$ of equation of state. In this paper we further study the cosmology of these solutions by analyzing them according to their asymptotic behaviors. The cosmology is classified into 19 phases according to the values of $γ$ and $ω$. The effect of the cosmological constant to the Brans-Dicke theory is a particular case of our model. We give plot of time evolution of the scale factor by numerical investigations. We also give a comparison of the solutions for the theories with and without matter.

gr-qc↗

arXiv1998

Thermodynamic Properties of Generalized Exclusion Statistics

We analytically calculate some thermodynamic quantities of an ideal $g$-on gas obeying generalized exclusion statistics. We show that the specific heat of a $g$-on gas ($g \neq 0$) vanishes linearly in any dimension as $T \to 0$ when the particle number is conserved and exhibits an interesting dual symmetry that relates the particle-statistics at $g$ to the hole-statistics at $1/g$ at low temperatures. We derive the complete solution for the cluster coefficients $b_l(g)$ as a function of Haldane's statistical interaction $g$ in $D$ dimensions. We also find that the cluster coefficients $b_l(g)$ and the virial coefficients $a_l(g)$ are exactly mirror symmetric ($l$=odd) or antisymmetric ($l$=even) about $g=1/2$. In two dimensions, we completely determine the closed forms about the cluster and the virial coefficients of the generalized exclusion statistics, which exactly agree with the virial coefficients of an anyon gas of linear energies. We show that the $g$-on gas with zero chemical potential shows thermodynamic properties similar to the photon statistics. We discuss some physical implications of our results.

cond-mat↗

arXiv1998

Notes on D-instanton correction to $AdS_5 \times S^5$ geometry

We show that the D-instanton in the $AdS_5 \times S^5$ background is a wormhole connecting the background $AdS_5 \times S^5$ to the flat space $\bf R^{10}$ located at the position of the D-instanton. By a $SL(2,{\bf R})$ rotation of type IIB theory, we can make the {\it global} geometry flat in string frame. We also find that, due to the tight relation between the dilaton and the axion, there is no $SL(2,{\bf R})$ element that takes strong string coupling to weak one without making the axion ill defined. We also discuss the case of $AdS_3$ as well as the instanton gases. A subtlety on the D-instanton at the boundary or at the horizon is discussed.

hep-th↗

arXiv1998

p-Brane cosmology and phases of Brans-Dicke theory with matter

We study the effect of the solitonic degrees of freedom in string cosmology following the line of Rama. The gas of solitonic p-brane is treated as a perfect fluid in a Brans-Dicke type theory. In this paper, we find exact cosmological solutions for any Brans-Dicke parameter $ω$ and for general parameter $γ$ of equation of state and classify the cosmology of the solutions on a parameter space of $γ$ and $ω$.

hep-th↗