arXiv subjects

Youngjai Kiem

Publications and source records attributed to Youngjai Kiem.

31 records · Page 2Linked to original sources

arXiv1998

Effective Action for Membrane Dynamics in DLCQ $M$ theory on a Two-torus

The effective action for the membrane dynamics on the background geometry of the $N$-sector DLCQ $M$ theory compactified on a two-torus is computed via supergravity. We compare it to the effective action obtained from the matrix theory, i.e., the (2+1)-dimensional supersymmetric Yang-Mills (SYM) theory, including the one-loop perturbative and full non-perturbative instanton effects. Consistent with the DLCQ prescription of $M$ theory {\em a la} Susskind, we find the precise agreement for the finite $N$-sector (off-conformal regime), as well as for the large $N$ limit (conformal regime), providing us with a concrete example of the correspondence between the matrix theory and the DLCQ $M$ theory. Non-perturbative instanton effects in the SYM theory conspire to yield the eleven-dimensionally covariant effective action.

hep-th↗

arXiv1998

Thermodynamics of doubly charged CGHS model and D1-D5-KK black holes of IIB supergravity

We study the doubly charged Callan-Giddings-Harvey-Strominger (CGHS) model, which has black hole solutions that were found to be U-dual to the D1-D5-KK black holes of the IIB supergravity. We derive the action of the model via a spontaneous compactification on S^3 of the IIB supergravity on S^1*T^4 and obtain the general static solutions including black holes corresponding to certain non-asymptotically flat black holes in the IIB supergravity. Thermodynamics of them is established by computing the entropy, temperature, chemical potentials, and mass in the two-dimensional setup, and the first law of thermodynamics is explicitly verified. The entropy is in precise agreement with that of the D1-D5-KK black holes, and the mass turns out to be consistent with the infinite Lorentz boost along the M theory circle that is a part of the aforementioned U-dual chain.

hep-th↗

arXiv1998

Background geometry of DLCQ M theory on a p-torus and holography

Via supergravity, we argue that the infinite Lorentz boost along the M theory circle a la Seiberg toward the DLCQ M theory compactified on a p-torus (p<5) implies the holographic description of the microscopic theory. This argument lets us identify the background geometries of DLCQ $M$ theory on a p-torus; for p=0 (p=1), the background geometry turns out to be eleven-dimensional (ten-dimensional) flat Minkowski space-time, respectively. Holography for these cases results from the localization of the light-cone momentum. For p = 2,3,4, the background geometries are the tensor products of an Anti de Sitter space and a sphere, which, according to the AdS/CFT correspondence, have the holographic conformal field theory description. These holographic descriptions are compatible to the microscopic theory of Seiberg based on $\tilde{M}$ theory on a spatial circle with the rescaled Planck length, giving an understanding of the validity of the AdS/CFT correspondence.

hep-th↗

arXiv1997

Infinite Lorentz boost along the M-theory circle and non-asymptotically flat solutions in supergravities

Certain non-asymptotically flat but supersymmetric classical solution of the type IIA supergravity can be interpreted as the infinitely-boosted version of the D-particle solution along the M-theory circle. By a chain of T-dual transformations, this analysis also applies to yield non-asymptotically flat solutions from the asymptotically flat and (non)-extremal solutions with intersecting D-strings and D five-branes of the type IIB supergravity compactified on a five-torus. Under S-duality, the non-asymptotically flat solutions in this context can in particular be used to describe the (1+1)-dimensional CGHS type black holes via spontaneous compactifications.

hep-th↗

arXiv1997

S-wave sector of type IIB supergravity on S^1 \times T^4

We consider the type IIB supergravity in ten dimensions compactified on S^1 \times T^4, with intersecting one and five D-branes in the compact dimensions. By imposing the spherical symmetry in the resulting five dimensional theory, we further reduce the s-wave sector of the theory to a two dimensional dilaton gravity. Via this construction, the techniques developed for the general two dimensional dilaton gravities are applicable in this context. Specifically, we obtain the bosonic sector general static solutions. In addition to the well-known asymptotically flat black hole solutions, they include solutions with naked singularities and non-asymptotically flat black holes.

hep-th↗

arXiv1996

General Static Spherical Solutions of d-dimensional Charged Dilaton Gravity Theories

We get the general static, spherically symmetric solutions of the d-dimensional Einstein-Maxwell-Dilaton theories by dimensionally reducing them to a class of 2-dimensional dilaton gravity theories. By studying the symmetries of the actions for the static equations of motion, we find field redefinitions that nearly reduce these theories to the d-dimensional Einstein-Maxwell-Scalar theories, and therefore enable us to get the exact solutions. We do not make any assumption about the asymptotic space-time structure. As a result, our 4-dimensional solutions contain the asymptotically flat Garfinkle-Horowitz-Strominger (GHS) solutions and the non-asymptotically flat Chan-Horne-Mann (CHM) solutions. Besides, we find some new solutions with a finite range of allowed radius of the transversal sphere. These results generalize to an arbitrary space-time dimension d (d>3).

hep-th↗

arXiv1996

Magnetically charged solutions via an analog of the electric-magnetic duality in (2+1)-dimensional gravity theories

We find an analog of the electric-magnetic duality, which is a $Z_2$ transformation between magnetic and electric sectors of the static and rotationally symmetric solutions in a class of (2+1)-dimensional Einstein-Maxwell-Dilaton gravity theories. The theories in our consideration include, in particular, one parameter class of theories continuously connecting the Banados-Teitelboim-Zanelli (BTZ) gravity and the low energy string effective theory. When there is no $U(1)$ charge, we have $O(2)$ or $O(1,1)$ symmetry, depending on a parameter that specifies each theory. Via the $Z_2$ transformation, we obtain exact magnetically charged solutions from the known electrically charged solutions. We explain the relationship between the $Z_2$ transformation and $O(2,Z)$ symmetry, and comment on the $T$-duality of the string theory.

hep-th↗

arXiv1996

Particle dynamics in a class of 2-dimensional gravity theories

We provide a method to determine the motion of a classical massive particle in a background geometry of 2-dimensional gravity theories, for which the Birkhoff theorem holds. In particular, we get the particle trajectory in a continuous class of 2-dimensional dilaton gravity theories that includes the Callan-Giddings-Harvey-Strominger (CGHS) model, the Jackiw-Teitelboim (JT) model, and the $d$-dimensional $s$-wave Einstein gravity. The explicit trajectory expressions for these theories are given along with the discussions on the results.

gr-qc↗

arXiv1996

General Static Solutions of 2-dimensional Einstein-Dilaton-Maxwell-Scalar Theories

General static solutions of effectively 2-dimensional Einstein-Dilaton-Maxwell-Scalar theories are obtained. Our model action includes a class of 2-d dilaton gravity theories coupled with a $U(1)$ gauge field and a massless scalar field. Therefore it also describes the spherically symmetric reduction of $d$-dimensional Einstein-Scalar-Maxwell theories. The properties of the analytic solutions are briefly discussed.

hep-th↗

arXiv1995

Black Hole Horizons and Complementarity

We investigate the effect of gravitational back-reaction on the black hole evaporation process. The standard derivation of Hawking radiation is re-examined and extended by including gravitational interactions between the infalling matter and the outgoing radiation. We find that these interactions lead to substantial effects. In particular, as seen by an outside observer, they lead to a fast growing uncertainty in the position of the infalling matter as it approaches the horizon. We argue that this result supports the idea of black hole complementarity, which states that, in the description of the black hole system appropriate to outside observers, the region behind the horizon does not establish itself as a classical region of space-time. We also give a new formulation of this complementarity principle, which does not make any specific reference to the location of the black hole horizon.

hep-th↗

arXiv1995

Static and Dynamic Analysis of a Massless Scalar Field Coupled with a Class of Gravity Theories

General static solutions for a massless scalar field coupled to a class of effectively 2-d gravity theories continuously connecting spherically symmetric $d$-dimensional Einstein gravity ($d >3$) and the CGHS model are analytically obtained. They include black holes and point scalar charge solutions with naked singularities, and are used to give an analytic proof of no-hair theorem. Exact scattering solutions in $s$-wave 4-d Einstein gravity are constructed as a generalization of corresponding static solutions. They show the existence of black hole formation threshold for square pulse type incoming stress-energy flux, above which trapped surfaces are dynamically formed. The relationship between this behavior and the numerically studied phase transition in this system \cite{choptuik} is discussed.

hep-th↗

arXiv1994

Phase Transition in Spherically Symmetric Gravitational Collapse of a Massless Scalar Field

Phase transition in spherically symmetric collapse of a massless scalar field is studied in 4-d Einstein gravity. A class of exact solutions that show the evolution of a constant incoming energy flux turned on at a point in the past null infinity are constructed to serve as an explicit example. The recently discovered phase transition in this system via numerical methods \cite{choptuik} is manifest; above a threshold value of the incooming energy flux, a black hole is dynamically formed and below that, the incoming flux is reflected forward into the future null infinity. The critical exponent is evaluated and discussed using the solutions.

hep-th↗

arXiv1993

An extension of Birkhoff's theorem to a class of 2-d gravity theories containing black holes

A class of 2-dimensional models including 2-d dilaton gravity, spherically symmetric reduction of d-dimensional Einstein gravity and other related theories are classically analyzed. The general analytic solutions in the absence of matter fields other than a U(1) gauge field are obtained under a new gauge choice and recast in the conventional conformal gauge. These solutions imply that Birkhoff's theorem, originally applied to spherically symmetric 4-d Einstein gravity, can be applied to all models we consider. Some issues related to the coupling of massless scalar fields and the quantization are briefly discussed.

hep-th↗