Shinji Hirano — Page 4

arXiv1997

Scattering of Closed String States from a Quantized D-Particle

By developing an appropriate path-integral formalism, we compute, in bosonic string theory, the disk amplitude for the scattering of closed string states from a D-particle, in which the collective coordinate of the D-particle is fully quantized. As a consequence, the recoil of the D-particle is naturally taken into account. Our result can be readily factorized in the closed string channel to yield the boundary state describing the recoiling D-particle. This turned out to agree with the BRST invariant vertex recently proposed by Ishibashi to the leading order in the derivative expansion, but it will receive corrections in subsequent orders. The advantage of our formalism is that it is extendable to deal with more general processes involving multiple D-particles. A viewpoint regarding our work as describing a dynamical transition of CFT's is also discussed.

hep-th↗

arXiv1994

Topological Structure in ${\hat c}=1$ Fermionic String Theory

$\chat=1$ fermionic string theory, which is considered as a fermionic string theory in two dimension, is shown to decompose into two mutually independent parts, one of which can be viewed as a topological model and the other is irrelevant for the theory. The physical contents of the theory is largely governed by this topological structure, and the discrete physical spectrum of $\chat=1$ string theory is naturally explained as the physical spectrum of the topological model. This topological structure turns out to be related with a novel hidden $N=2$ superconformal algebra (SCA) in the enveloping algebra of the $N=3$ SCA in fermionic string theories.

hep-th↗