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Y. S. Myung

Publications and source records attributed to Y. S. Myung.

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

Greybody factor for D3-branes in B field

We calculate the effect of noncommutative spacetime on the greybody factor on the supergravity side. For this purpose we introduce a system of D3-branes with a constant NS $B$-field along their world volume directions ($x_2, x_3$). Considering the propagation of minimally coupled scalar with non-zero momentum along($x_2, x_3$), we derive an exact form of the greybody factor in $B$ field. It turns out that $σ^{B\ne0}_l > σ^{B=0}_l$. This means that the presence of $B$-field (the noncommutativity) suppresses the potential barrier surrounding the black hole. As a result, it comes out the increase of greybody factor.

hep-th↗
arXiv2000

Comment on "Metric Fluctuations in Brane Worlds"

Recently, Ivanov and Volovich (hep-th/9912242) claimed that the perturbation of $h_{μν}$ with nonvanishing transverse components $h_{5μ}$ is not localized on the brane because $h_{μν}$ depends on the fifth coordinate $z$ linearly. Consequently, it may indicate that the effective theory is unstable. However, we point out that such linear dependence on $z$ can be {\it gauged away}. Hence the solution does not belong to the physical one. Therefore, even if one includes $h_{5μ}$, Randall and Sundrum's argument for the localized gravity on the brane remains correct.

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arXiv1999

Noncommutative spacetime and the fractional quantum Hall effect

We propose the two formalisms for obtaining the noncommutative spacetime in a magnetic field. One is the first-order formalism and the other is the second-order formalism. Although the noncommutative spacetime is realized manifestly in the first-order formalism, the second-order formalism would be more useful for calculating the physical quantities in the noncommutative geometry than the first-order one. Several interesting points for string theory and fractional quantum Hall effect are discussed. In particular, we point out that the noncommutative geometry is closely related to the fractional quantum Hall effect(FQHE).

hep-th↗
arXiv1999

Scattering from an AdS_3 bubble and an exact AdS_3

We investigate the close relationship between the potential and absorption cross section for test fields in an AdS$_3$ bubble(a 5D black hole) and an exact AdS$_3$. There are two solutions in type IIB string theory: an AdS$_3$ bubble corresponds to the dilatonic solution, while an exact AdS$_3$ is the non-dilatonic solution. In order to obtain the cross section for an AdS$_3$ bubble, we introduce the \{out\}-state scattering picture with the AdS$_3$-AFS matching procedure. For an exact AdS$_3$, one considers the \{in\}-state scattering picture with the AdS$_3$-AdS$_3$ matching. Here the non-normalizable modes are crucially taken into account for the matching procedure. It turns out that the cross sections for the test fields in an AdS$_3$ bubble take the same forms as those in an exact AdS$_3$. This suggests that in the dilute gas and the low energy limits, the S-matrix for an AdS$_3$ bubble can be derived from an exact AdS$_3$ space.

hep-th↗
arXiv1999

Dilaton test of connection between AdS_3 X S^3 and 5D black hole

A 5D black hole(M$_5$) is investigated in the type IIB superstring theory compactified on S$^1 \times $T$^4$. This corresponds to AdS$_3 \times $S$^3 \times $T$^4$ in the near horizon with asymptotically flat space. Here the harmonic gauge is introduced to decouple the mixing between the dilaton and others. On the other hand we obtain the BTZ balck hole(AdS$_3\times$S$^3\times$T$^4$) as the non-dilatonic solution. We calculate the greybody factor of the dilaton as a test scalar both for a 5D black hole(M$_5 \times $S$^1 \times $T$^4$) and the BTZ black hole(AdS$_3 \times $S$^3 \times $T$^4$). The result of the BTZ black hole agrees with the greybody factor of the dilaton in the dilute gas approximation of a 5D black hole.

hep-th↗
arXiv1999

Noncommutative Geometry and Anyonic Field Theory in the Magnetic Field

We consider an easy way to get the noncommutative spacetime in Minkowski space. This corresponds to introducing a magnetic field ${\rm\bf B} = B \hat {\rm\bf k}$ in the plane. We construct a green's function in coordinate space which includes a Moyal phase factor. The projection to the lowest Landau level(LLL) is necessary for a simple calculation. Using this green's function and a second quantized formalism, we study the thermodynamic property of the anyons on the noncommutative geometry. It turns out that the Moyal phase factors contribute to the thermodynamic potential $Ω$ as opposed to the free-particle nature.

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arXiv1999

Gauge bosons and the AdS_3/LCFT_2 correspondence

We study the relationship between the gauge boson coupled to spin 2 operator and the singleton in three-dimensional anti-de Sitter space(AdS$_3$). The singleton can be expressed in terms of a pair of dipole ghost fields $A$ and $B$ which couple to $D$ and $C$ operators on the boundary of AdS$_3$. These operators form the logarithmic conformal field theory(LCFT$_2$). Using the correlation function for logarithmic pair, we calculate the greybody factor for the singleton. In the low temperature limit of $ω\gg T_{\pm}$, this is compared with the result of the bulk AdS$_3$ calculation of the gauge boson. We find that the gauge boson cannot be realized as a model of the AdS$_3$/LCFT$_2$ correspondence.

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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.

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arXiv1999

6D black string as a model of the AdS/CFT correspondence

We discuss the entropy for the extremal BTZ black hole and the extremal EBTZ black hole. The EBTZ black hole means the BTZ black hole embedded in a five-dimensional(5D) black hole. The six-dimensional(6D) black string with traveling waves is introduced as a concrete model for realizing the AdS/CFT correspondence. The traveling waves carry the momentum distribution $p(u)$ which plays an important role in counting the entropy and establishing the correspondence. It turns out that the EBTZ black hole is consistent with the AdS/CFT correspondence.

hep-th↗
arXiv1998

BTZ black hole and quantum Hall effect in the bulk/boundary dynamics

We point out an interesting analogy between the BTZ black hole and QHE (Quantum Hall effect) in the (2+1)-dimensional bulk/boundary theories. It is shown that the Chern-Simons/Liouville(Chern-Simons/chiral boson) is an effective description for the BTZ black hole (QHE). Also the IR(bulk)-UV(boundary) connection for a black hole information bound is realized as the UV(low-lying excitations on bulk)-IR(long-range excitations on boundary) connection in the QHE. An inflow of conformal anomaly($c=1$ central charge) onto the timelike boundary of AdS$_3$ by the Noether current corresponds to an inflow of chiral anomaly onto the edge of disk by the Hall current.

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

Dynamical Behavior of the BTZ Black Hole

We study the dynamical behavior of the BTZ (Banados-Teitelboim-Zanelli) black hole with the low-energy string effective action. The perturbation analysis around the BTZ black hole reveals a mixing between the dilaton and other fields. Introducing the new gauge (dilaton gauge), we disentangle this mixing completely and obtain one decoupled dilaton equation. We obtain the decay rate $Γ$ of BTZ black hole.

hep-th↗
arXiv1998

Greybody factor for the BTZ black hole and a 5D black hole

We study the 5D black holes in the type IIB superstring theory compactified on $S^1 \times T^4$. Far from horizon, we have flat space-time. Near horizon, we have $AdS_3(BTZ black hole) \times S^3 \times T^4$. We calculate the greybody factor of a minimally coupled scalar by replacing the original geometry($M_5 \times S^1 \times T^4$) by $AdS_3 \times S^3 \times T^4$. In the low-energy scattering, it turns out that the result agrees with the greybody factor of the 5D black hole (or D1 + D5 branes)in the dilute gas approximation. This confirms that the $AdS$-theory($AdS_3 \times S^3 \times T^4$) contains the essential information about the bulk 5D black holes.

hep-th↗
arXiv1998

Entropy Problem in the AdS$_3$/CFT correspondence

We resolve the entropy problem in the AdS$_3$/CFT correspondence by introducing both the normalizable and non-normalizable bulk modes. On the boundary, the normalizable Liouville states gives us $c=1$ conformal field theory(CFT), whereas the non-normalizable Liouville states provide $c = {3 \ell \over 2 G}$ CFT. Such (boundary) non-normalizable modes come from non-normalizable bulk modes which serve as classical, non-fluctuating bulk background and encode the choice of local operator insertion on the boundary. Since the non-normalizable bulk modes can transfer information from bulk to boundary, it suggests that counting of non-normalizable states on the boundary at infinity leads to the entropy($S={2 πr_+ \over 4 G}$) of (2+1)-dimensional gravity with $ Λ= -1/\ell^2$.

hep-th↗
arXiv1998

Greybody Factors in the $AdS_3$/CFT Correspondence

We propose a new method to calculate the greybody factor in the $AdS_3$. This is based on both the non-normalizable modes of a test field($Φ_i$) and $AdS_3$/CFT correspondence. Such non-normalizable modes serve as classical, non-fluctuating background and encode the choice of operator insertion(${\cal O}^i$) in the boundary. Actually specifying the boundary condition at infinity of $AdS_3$ corresponds to turning on these non-normalizable modes. Hence we can calculate the greybody factor of test fields without the Dirichlet(or Neumann) boundary condition. The result is consistent with those of the boundary CFT and effective string calculations.

hep-th↗
arXiv1998

Potential analysis and absorption cross section in the D1-D5 brane system

We analyze the potentials which arise from the D1--D5 brane (5D black hole). In the sufficiently low energy ($ω\ll 1$), we can derive the Schrodinger-type equation with potential $V_N$ from the linearized equations. In this case one can understand the difference between absorption cross section for a free and two fixed scalars intuitively in terms of their potentials. In the low temperature limit ($ω\gg T_H$), one expects the logarithmic correction to the cross section of a free scalar. However, we cannot obtain the Schrodinger equation with potential for this case. Finally we comment on the stability of 5D black hole.

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