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Won Tae Kim

Publications and source records attributed to Won Tae Kim.

At least 37 records · Page 2Linked to original sources
arXiv2000

BFT embedding of noncommutative D-brane system

We study noncommutative geometry in the framework of the Batalin-Fradkin-Tyutin(BFT) scheme, which converts second class constraint system into first class one. In an open string theory noncommutative geometry appears due to the mixed boundary conditions having second class constraints, which arise in string theory with $D$-branes under a constant Neveu-Schwarz $B$-field. Introduction of a new coordinate $y$ on $D$-brane through BFT analysis allows us to obtain the commutative geometry with the help of the first class constraints, and the resulting action corresponding to the first class Hamiltonian in the BFT Hamiltonian formalism has a new local symmetry.

hep-th↗
arXiv2000

Global embeddings of scalar-tensor theories in (2+1)-dimensions

We obtain (3+3)- or (3+2)-dimensional global flat embeddings of four uncharged and charged scalar-tensor theories with the parameters B or L in the (2+1)-dimensions, which are the non-trivially modified versions of the Banados-Teitelboim-Zanelli (BTZ) black holes. The limiting cases B=0 or L=0 exactly are reduced to the Global Embedding Minkowski Space (GEMS) solution of the BTZ black holes.

gr-qc↗
arXiv1999

Noncommutative open strings from Dirac quantization

We study Dirac commutators of canonical variables on D-branes with a constant Neveu-Schwarz 2-form field by using the Dirac constraint quantization method, and point out some subtleties appearing in previous works in analyzing constraint structure of the brane system. Overcoming some ad hoc procedures, we obtain desirable noncommutative coordinates exactly compatible with the result of the conformal field theory in recent literatures. Furthermore, we find interesting commutator relations of other canonical variables.

hep-th↗
arXiv1999

Massless vs. Massive Hawking Radiation in AdS$_2$ Spacetime

We study massless and massive Hawking radiations on a two-dimensional AdS spacetime. For the massless case, the quantum stress-energy tensor of a massless scalar field on the AdS background is calculated, and the expected null radiation is obtained. However, for the massive case, the scattering analysis is performed in order to calculate the absorption and reflection coefficients which are related to statistical Hawking temperature. On the contrary to the massless case, we obtain a nonvanishing massive radiation.

hep-th↗
arXiv1999

Improved BFT quantization of O(3) nonlinear sigma model

We newly apply the improved Batalin-Fradkin-Tyutin(BFT) Hamiltonian method to the O(3) nonlinear sigma model, and directly obtain the compact form of nontrivial first class Hamiltonian by introducing the BFT physical fields. Furthermore, following the BFV formalism, we derive the BRST invariant gauge fixed Lagrangian through the standard path-integral procedure. Finally, by introducing collective coordinates, we also study a semi-classical quantization of soliton background to conclude that the spectrum of zero modes are unchanged through the BFT procedure.

hep-th↗
arXiv1999

Dilaton driven Hawking radiation in AdS$_2$ black hole

A recent study shows that Hawking radiation of the massless scalar field does not appear on the two-dimensional AdS$_2$ black hole background. We study this issue by investigating absorption and reflection coefficients under dilaton coupling with the matter field. If the scalar field does not couple to the dilaton, then it is fully absorbed into the black hole without any outgoing mode. On the other hand, once it couples to the dilaton field, the outgoing mode of the massless scalar field exists and the nontrivial Hawking radiation is obtained. Finally, we comment on this dilaton dependence of Hawking radiation in connection with a three-dimensional black hole.

hep-th↗
arXiv1999

AdS_2 and quantum stability in the CGHS model

The two-dimensional anti-de Sitter space(AdS_2) is constructed in terms of the CGHS model. The geometric solutions are composed of the AdS vacuum and the AdS black hole which are locally equivalent but distinguishable by their mass. The infalling classical fields do not play any role but the quantum back reaction is crucial in the formation of the AdS vacuum and AdS black hole. In the presence of the AdS black hole, there does not exist any radiation, which is consistent with the constraint equations. Therefore the transition from the AdS black hole to the AdS vacuum is impossible, and they are quantum mechanically stable . We discuss the reason why the vanishing Hawking radiation appears in the AdS_2 black hole in contrast to asymptotically flat black holes.

hep-th↗
arXiv1999

Statistical Entropy and AdS/CFT Correspondence in BTZ Black Holes

We study AdS/CFT correspondence in the case of AdS3. We obtain the statistical entropy of the BTZ black hole in terms of the correct central charge and the conformal dimensions for the states corresponding to the BTZ black hole. We point out the difference between our method and the old fashioned approaches based on SL(2,R) Wess-Zumino-Witten model or Liouville theory.

hep-th↗
arXiv1998

Batalin-Vilkovisky quantization of symmetric Chern-Simons theory

We study the manifestly covariant three-dimensional symmetric Chern-Simons action in terms of the Batalin-Vilkovisky quantization method. We find that the Lorentz covariant gauge fixed version of this action is reduced to the usual Chern-Simons type action after a proper field redefinition. Furthermore, the renormalizability of the symmetric Chern-Simons theory turns out to be the same as that of the original Chern-Simons theory.

hep-th↗
arXiv1998

Manifestly covariant action for symmetric Chern-Simons field theory

We study a three-dimensional symmetric Chern-Simons field theory with a general covariance and it turns out that the original Chern-Simons theory is just a gauge fixed action of the symmetric Chern-Simons theory whose constraint algebra belongs to fully first class constraint system. The Abelian Chern-Simons theory with matter coupling is studied for the construction of anyon operators without any ordering ambiguity with the help of this symmetric Chern-Simons action. Finally we shall discuss some connections between the present symmetric formulation of Chern-Simons theory and the Stükelberg mechanism.

hep-th↗
arXiv1998

Symplectic structure free Chern-Simons Theory

The second class constraints algebra of the abelian Chern-Simons theory is rigorously studied in terms of the Hamiltonian embedding in order to obtain the first class constraint system. The symplectic structure of fields due to the second class constraints disappears in the resulting system. Then we obtain a new type of Chern-Simons action which has an infinite set of the irreducible first class constraints and exhibits new extended local gauge symmetries implemented by these first class constraints.

hep-th↗
arXiv1998

Initial singularity free quantum cosmology in two-dimensional Brans-Dicke theory

We consider two-dimensional Brans-Dicke theory to study the initial singularity problem. It turns out that the initial curvature singularity can be finite for a certain Brans-Dicke constant $ω$ by considering the quantum back reaction of the geometry. For $ω=1$, the universe starts with the finite curvature scalar and evolves into the flat spacetime. Furthermore the divergent gravitational coupling at the initial time can be finite effectively with the help of quantum correction. The other type of universe is studied for the case of $0<ω<1$.

hep-th↗
arXiv1998

Remarks on self-dual formulation of Born-Infeld-Chern-Simons theory

We study the self-duality of Born-Infeld-Chern-Simons theory which can be interpreted as a massive D2 brane in IIA string theory and exhibit the self-dual formulation in terms of the gauge invariant master Lagrangian. The proposed master Lagrangian contains the nonlocal auxiliary field and approaches self-dual formulation of Maxwell-Chern-Simons theory in a point-particle limit with the weak string-coupling limit. The consistent canonical brackets of dual system are derived.

hep-th↗
arXiv1998

Duality of Quasilocal Black Hole Thermodynamics

We consider T-duality of the quasilocal black hole thermodynamics for the three-dimensional low energy effective string theory. Quasilocal thermodynamic variables in the first law are explicitly calculated on a general axisymmetric three-dimensional black hole solution and corresponding dual one. Physical meaning of the dual invariance of the black hole entropy is considered in terms of the Euclidean path integral formulation.

gr-qc↗
arXiv1997

Graceful exit problem and stress-energy-momentum tensors revisited in the two-dimensional string cosmology

We study the graceful exit problem and the role of the stress-energy-momentum tensors in the two-dimensional string cosmology. The one-loop quantum correction of conformal fields is incorporated in the arbitrary large $N$ limit to ensure exact quantum solvability. The only solution which gives the bounded curvature with the asymptotic flatness is restricted to the first branch under some conditions. However, even in this case, the accelerating expansion is forever. We show that the only nonvanishing quantum stress-momentum tensor is the pressure part($T_{xx}$) which is of relevance to the dynamical evolution of the universe in the comoving coordinate. The quantum energy part is zero since the negative contribution of the induced conformal matters always cancels the positive quantity of the induced dilaton part in terms of the constraint equation.

hep-th↗
arXiv1997

Entropy in the Kerr-Newman Black Hole

Entropy of the Kerr-Newman black hole is calculated via the brick wall method with maintaining careful attention to the contribution of superradiant scalar modes. It turns out that the nonsuperradinat and superradiant modes simultaneously contribute to the entropy with the same order in terms of the brick wall cutoff $ε$. In particular, the contribution of the superradiant modes to the entropy is negative. To avoid divergency in this method when the angular velocity tends to zero, we propose to intr oduce a lower bound of angular velocity and to treat the case of the angular momentum per unit mass $a=0$ separately. Moreover, from the lower bound of the angular velocity, we obtain the $θ$-dependence structure of the brick wall cutoff, which natu rally requires an angular cutoff $δ$. Finally, if the cutoff values, $ε$ and $δ$, satisfy a proper relation between them, the resulting entropy satisfies the area law.

gr-qc↗