Dongsu Bak
Seoul National University
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Featured researches published by Dongsu Bak.
Journal of High Energy Physics | 2003
Dongsu Bak; Michael Gutperle; Shinji Hirano
We find a nonsupersymmetric dilatonic deformation of AdS5 geometry as an exact nonsingular solution of the type-IIB supergravity. The dual gauge theory has a different Yang-Mills coupling in each of the two halves of the boundary spacetime divided by a codimension one defect. We discuss the geometry of our solution in detail, emphasizing the structure of the boundary, and also study the string configurations corresponding to Wilson loops. We also show that the background is stable under small scalar perturbations.
Journal of High Energy Physics | 2007
Dongsu Bak; Andreas Karch; Laurence G. Yaffe
Using the AdS/CFT correspondence, we examine the behavior of correlators of Polyakov loops and other operators in = 4 supersymmetric Yang-Mills theory at non-zero temperature. The implications for Debye screening in this strongly coupled non-Abelian plasma, and comparisons with available results for thermal QCD, are discussed.
Physics Letters B | 2001
Dongsu Bak; Kimyeong Lee
Abstract We investigate supersymmetric tubular configurations in the matrix theory. We construct a host of BPS configurations of eight supersymmetries. They can be regarded as cylindrical D2 branes carrying nonvanishing angular momentum. For the simplest tube, the world volume can be described as noncommutative tube and the world volume dynamics can be identified as a noncommutative gauge theory. Among the BPS configurations, some describe excitations on the tube and others describe many parallel tubes of different size and center.
Journal of High Energy Physics | 2008
Dongsu Bak; Dongmin Gang; Soo-Jong Rey
= 6 superconformal Chern-Simons theory with gauge group U(M) × is dual to N M2-branes and (M−N) fractional M2-branes, equivalently, discrete 3-form holonomy at 4/k orbifold singularity. We show that, much like its regular counterpart of M = N, the theory at planar limit have integrability structure in the conformal dimension spectrum of single trace operators. We first revisit the Yang-Baxter equation for a spin chain system associated with the single trace operators. We show that the integrability by itself does not preclude parity symmetry breaking. We construct two-parameter family of parity non-invariant, alternating spin chain Hamiltonian involving three-site interactions between 4 and of SU(4)R. At weak `t Hooft coupling, we study the Chern-Simons theory perturbatively and calculate anomalous dimension of single trace operators up to two loops. The computation is essentially parallel to the regular case M = N. We find that resulting spin chain Hamiltonian matches with the Hamiltonian derived from Yang-Baxter equation, but to the one preserving parity symmetry. We give several intuitive explanations why the parity symmetry breaking is not detected in the Chern-Simons spin chain Hamiltonian at perturbative level. We suggest that open spin chain, associated with open string excitations on giant gravitons or dibaryons, can detect discrete flat holonomy and hence parity symmetry breaking through boundary field.
Nuclear Physics | 2002
Dongsu Bak; Andreas Karch
Abstract We find a class of flat supersymmetric brane–antibrane configurations. They follow from ordinary brane–antibrane systems by turning on a specific worldvolume background electric field, which corresponds to dissolved fundamental strings. We have clarified in detail how they arise and identified their constituent charges as well as the corresponding supergravity solutions. Adopting the matrix theory description, we construct the worldvolume gauge theories and prove the absence of any tachyonic degrees. We also study supersymmetric solitons of the worldvolume theories.
Nuclear Physics | 2005
Dongsu Bak; Yoshifumi Hyakutake; Seok Kim; Nobuyoshi Ohta
Abstract We give a geometric interpretation of the entropy of the supertubes with fixed conserved charges and angular momenta in two different approaches using the DBI action and the supermembrane theory. By counting the geometrically allowed microstates, it is shown that both the methods give consistent result on the entropy. In doing so, we make the connection to the gravity microstates clear.
Physics Letters B | 2002
Dongsu Bak; Nobuyoshi Ohta
Abstract We consider the flat supersymmetric D2 and anti-D2 system, which follows from ordinary noncommutative D2–anti-D2 branes by turning on an appropriate worldvolume electric field describing dissolved fundamental strings. We study the strings stretched between D2 and anti-D2 branes and show explicitly that the would-be tachyonic states become massless. We compute the string spectrum and clarify the induced noncommutativity on the worldvolume. The results are compared with the matrix theory description of the worldvolume gauge theories.
Physical Review Letters | 2001
Dongsu Bak; Kimyeong Lee; Jeong-Hyuck Park
We investigate U(N) Chern-Simons theories on the noncommutative plane. We show that for the theories to be consistent quantum mechanically, the coefficient of the Chern-Simons term should be quantized kappa = n/2pi with an integer n. This is a surprise for the U(1) gauge theory. When uniform background charge density rho(e) is present, the quantization rule changes to kappa+rho(e)straight theta = n/2pi with the noncommutative parameter straight theta. With the exact expression for the angular momentum, we argue in the U(1) theory that charged particles in the symmetric phase carry fractional spin 1/2n and vortices in the broken phase carry half-integer or integer spin -n/2.
Nuclear Physics | 2004
Dongsu Bak; Yoshifumi Hyakutake; Nobuyoshi Ohta
We study possible deformations of BPS supertubes keeping their conserved charges fixed. We show that there is no flat direction to closed supertubes of circular cross section with uniform electric and magnetic fields, and also to open planar supertubes. We also find that there are continuously infinite flat deformations to supertubes of general shape under certain conditions.
Physical Review D | 2003
Dongsu Bak
We consider the matrix model associated with pp-wave background and construct supersymmetric branes. In addition to the spherical membrane preserving 16 supersymmetries, one may construct rotating elliptic membranes preserving 8 supersymmetries. The other branch describes rotating 1/8 BPS hyperbolic branes in general. When the angular momentum vanishes in this branch, the hyperbolic brane becomes 1/4 BPS preserving 8 real supersymmetries. It may have the shape of hyperboloid of one or two sheets embedded in the flat three space. We study the spectrum of the worldvolume fields on the hyperbolic branes and show that there are no massless degrees. We also compute the spectrum of the 0-2 strings.