Myung Seok Yoon

Traversable wormhole construction in 2+1 dimensions

We have studied traversable Lorentzian wormholes by adding some matter source involving a dilaton field into the three-dimensional low-energy string theory. Through this experiment, it was shown that there were two types of wormhole solutions\char22{}the BTZ and black string wormholes\char22{}depending on the dilaton backgrounds, respectively. We are finally able to obtain desirable solutions that confine exotic matter near the throat of a wormhole by adjusting the NS charge.

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 \ensuremath{\omega} by considering the quantum back reaction of the geometry. For

Batalin-Fradkin-Tyutin embedding of a noncommutative D-brane system

\ensuremath{\omega}=1,

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

the universe starts with the finite curvature scalar and evolves into flat spacetime. Furthermore the divergent gravitational coupling at initial time can be finite effectively with the help of quantum correction. The other type of universe is studied for the case of

Positive Equation-of-State Parameter in the Accelerating Dilaton Cosmology

0l\ensuremath{\omega}l1.

Batalin-Fradkin-Tyutin embedding of noncommutative chiral bosons

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

Brane-World Black Holes in Randall-Sundrum Models

D

Manifestly covariant action for symmetric Chern-Simons field theory

-branes under a constant Neveu-Schwarz

Remarks on the wave function of the universe in the dilaton cosmology

B