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Jin Young Kim

Publications and source records attributed to Jin Young Kim.

At least 55 records · Page 3Linked to original sources
arXiv2000

Dilaton-driven brane inflation in type IIB string theory

We consider the cosmological evolution of the three-brane in the background of type IIB string theory. For two different backgrounds which give nontrivial dilaton profile we have derived the Friedman-like equations. These give the cosmological evolution which is similar to the one by matter density on the universe brane. The effective density blows up as we move towards the singularity showing the initial singularity problem. The analysis shows that when there is axion field in the ambient space the recollapsing of the universe occurs faster compared with the case without axion field.

hep-th↗
arXiv2000

Absorption of dilaton s-wave in type 0B string theory

We find the absorption probability of dilaton field in type 0B string theory. Since the background solutions are of the form $AdS_5 \times S^5$ on both regions, we use the semiclassical formalism adopted in type IIB theory to find the absorption cross section. The background tachyon field solution was used as a reference to relate the solutions of the two regions. We also consider the possible corrections to absorption probability and the $\ln(\ln z)$ form of the correction is expected as in the calculation of the confinement solution.

hep-th↗
arXiv1999

Tachyon and fixed scalars of D5$_\pm$-D1$_\pm$ black hole in type 0B string theory

In the type 0B string theory, we discuss the role of tachyon($T$) and fixed scalars($ν,λ$). The issue is to explain the difference between tachyon and fixed scalars in the D$5_{\pm}$-D$1_{\pm}$ black hole background. For this purpose, we perform the semiclassical calculation. Here one finds a mixing between ($ν, λ, T$) and the other fields. Using the decoupling procedure, one finds the linearized equation for the tachyon. From the potential analysis, it turns out that $ν$ plays a role of test field well, while the tachyon induces an instability of Minkowski space vacuum. But the roles of $ν$ and $T$ are the same in the near-horizon geometry. Finally we discuss the stability problem.

hep-th↗
arXiv1999

New gauge bosons and logarithmic corrections in an exact AdS$_3$

We calculate the absorption cross section by studying the spin--dependent wave equation in three-dimensional anti-de Sitter space(AdS$_3$). Here the AdS/CFT correspondence is used. It turns out that the new gauge bosons coupled to (2,0) and (0,2) operators on the boundary at infinity receive logarithmic corrections. This shows that the gauge bosons may play the role of singletons in AdS$_5$. On the other hand, test fields including the intermediate scalars($η, ξ$) and fixed scalar($λ$) do not receive any logarithmic correction in the first-order approximation.

hep-th↗
arXiv1998

The role of fixed scalars in scattering off a 5D black hole

We discuss the role of fixed scalars($ν,λ$) in scattering off a five-dimensional balck hole. The issue is to explain the disagreement of the greybody factor for $λ$ between the semiclassical and effective string calculations. In the effective string approach, this is related to the operators with dimension (3,1) and (1,3). On the semiclassical calculation, this originates from a complicated mixing between $λ$ and other fields. Hence it may depend on the decoupling procedure. It is shown that $λ$ depends on the gauge choices such as the harmonic, dilaton gauges, and the Krasnitz-Klebanov setting for $h_{μν}$. It turns out that $ν$ plays a role of test field well, while the role of $λ$ is obscure.

hep-th↗
arXiv1998

Stability analysis and absorption cross-section in three-dimensional black string

It is shown that all string fields except dilaton are non-propagating in the (2+1)-dimensional black string. One finds that the perturbation around the black string reveals a mixing between the dilaton and other fields. Under the new gauge(dilaton gauge), we disentangle this mixing and obtain one decoupled dilaton equation. It turns out that this black string is stable. From the scattering of dilaton off the neutral black string(N=0), we find the absorption cross-section. Further the absorption cross-section for minimally coupled scalar is obtained and we compared it with that of dilaton.

hep-th↗
arXiv1997

Negative modes in the four-dimensional stringy wormholes

We study the Giddings-Strominger wormholes in string theories. We found negative modes among O(4)-symmetric fluctuations about the non-singular wormhole background. Hence the stringy wormhole contribution to the euclidean functional integral is purely imaginary. This means that the stringy wormhole is a bounce (not an instanton) and describes the nucleation and growth of wormholes in the Minkowski spacetime.

hep-th↗
arXiv1997

Absorption of fixed scalar in scattering off 4D N=4 black holes

We perform the perturbation analysis of the black holes in the 4D, N=4 supergravity. Analysis around the black holes reveals a complicated mixing between the dilaton and other fields (metric and two U(1) Maxwell fields). It turns out that considering both s-wave (l=0) and higher momentum modes (l \neq 0), the dilaton as a fixed scalar is the only propagating mode with $P=Q, h_1=h_2=0$ and $F = -G = 2ϕ$. We calculate the absorption cross-section for scattering of low frequency waves of fixed scalar and U(1) Maxwell fields off the extremal black hole.

hep-th↗
arXiv1997

Propagating waves in an extremal black string

We investigate the black string in the context of the string theories. It is shown that the graviton is the only propagating mode in the (2+1)--dimensional extremal black string background. Both the dilation and axion turn out to be non-propagating modes.

hep-th↗
arXiv1996

Higher dimensional extremal black strings

We investigate the five and six-dimensional black strings within Einstein-Maxwell theory. The extremal black strings are endowed with the null Killing symmetry. We study the propagation of Einstein-Maxwell modes in the extremal black string background by using this symmetry. It turns out that one graviton is a propagating mode, while both the Maxwell $F$ and three-form $H$ fields are non-propagating modes. Further we discuss the stability and classical hair of the extremal black strings.

hep-th↗
arXiv1996

Comment on "Background thermal contributions in testing the Unruh effect"

Costa and Matsas (gr-qc/9412030) claimed in their recent paper that a thermal bath does not affect substantially the transition probability for fast moving inertial Unruh detector. It is shown that their claim holds only for small $βΔE$. We show that, for large enough $βΔE$, the transition probability is not monotonically decreasing function of the detector's speed contrary to their claim.

hep-th↗
arXiv1996

New divergences of tachyon in the two-dimensional charged black holes

We quantize the tachyon field in the two-dimensional (2D), $ε<2$ charged black holes where $ε$ is the dilaton coupling parameter for the Maxwell term. Especially the expectation value of the stress-energy tensor $\langle T_{ab}\rangle$, observed by a freely falling observer, is computed. This shows that new divergences such as $\ln f$ and ${1 \over f}$ arises near the horizon ($f \to 0$), compared with conformal matter case.

hep-th↗
arXiv1995

Two-dimensional extremal black holes

We discuss the two-dimensional (2D), $ε<2$ extremal ground states of charged black hole. Here $ε$ is the dilaton coupling parameter for the Maxwell term. The complete analysis of stability is carried out for all these extremal black holes. It is found that they are all unstable. To understand this instability, we study the non-extremal charged black hole with two (inner and outer) horizons. The extremal black holes appear when two horizons coalesce. It conjectures that the instability originates from the inner horizon.

hep-th↗
arXiv1995

Anomalous Magnetic Moment of Anyons in three dimensional $CP^{N-1}$ Model

We calculate the anomalous magnetic moment of anyons in three dimensional $CP^{N-1}$ model with a Chern-Simons term in various limits in $1/N$ expansion. We have found that for anyons of infinite mass the gyromagnetic ratio ($g$-factor) is 2 up to the next-to-leading order in $1/N$. Our result supports a recent claim that the $g$-factor of nonrelativistic anyons is exactly two. We also found that for $-{8\overπ}<θ<0$, the electromagnetic interation between two identical aynons of large mass are attractive.

hep-th↗
arXiv1995

Unstable two-dimensional extremal black holes

We obtain the $ε<2$ new extremal ground states of a two-dimensional (2D) charged black hole where $ε$ is the dilaton coupling parameter for the Maxwell term. The stability analysis is carried out for all these extremal black holes. It is found that the shape of potentials to an on-coming tachyon (as a spectator) take all barrier-well types. These provide the bound state solutions, which imply that they are unstable. We conclude that the 2D, $ε<2$ extremal black holes should not be considered as a toy model for the stable endpoint of the Hawking evaporation.

hep-th↗
arXiv1995

Blushift of a tachyon in the charged 2D black hole

We study the propagation of string fields (metric $G_{μν}$, Mawxell gauge potential $A_μ$, dilaton $Φ$, and tachyon $T$) in a two-dimensional (2D) charged black hole. It is shown that the tachyon is a propagating field both inside and outside the black hole. This becomes infinitely blueshifted at the inner horizon. We confirm that the inner horizon is unstable, whereas the outer horizon is stable.

hep-th↗