arXiv subjects
Publications and source records attributed to In-guy Koh.
A first order inflation model where a gauge coupling constant runs as the universe inflates is investigated. This model can solve the graceful-exit problem within Einstein gravity by varying the bubble formation rate. The sufficient expansion condition gives group theoretical constraints on the inflaton field, while the appropriate density perturbation requires an additional scalar field or cosmic strings.
An inflation model with inverse symmetry breaking of two scalar fields is proposed. Constraints on the parameters for a successful inflation are obtained. In general the inequality $λ_1\ll g <λ_2$ should be satisfied, where $λ_{1,2}$ and $g$ are the coupling constants for self interaction and mutual interaction of two scalar fields respectively. An example with $SU(5)$ GUTs phase transition and numerical study are presented. This model introduce a new mechanism for the onset of inflation.
We study fermion reflection at a phase wave which is formed during a bubble collision in a first order phase transition. We calculate the reflection and the transmission coefficients by solving the Dirac equation with the phase wave background. Using the results we analyze the damping and the velocity of the wave.
We investigate the boson star with the self-interacting scalar field as a model of galactic halos. The model has slightly increasing rotation curves and allows wider ranges of the mass($m$) and coupling($λ$) of the halo dark matter particle than the non-interacting model previously suggested(ref.\cite{sin1}). Two quantities are related by $λ^{\frac{1}{2}} (m_p/m)^2\st{>}{\sim} 10^{50}$.