Non-BPS D0-brane instanton effects in type I string theory

We investigate the instanton effects of non-BPS D0-brane in type I string theory. We argue the general properties of these instanton effects and consider these on $R^9\times S^1$ as a simple example using the effective action of D0-brane.Comment: LaTex, 12 pages, no figures, Some incorrect sentences in section 2 are corrected or removed, 1 reference added, minor correction

Comments on Solutions for Nonsingular Currents in Open String Field Theories

We investigate analytic solutions to Witten's bosonic string field theory and Berkovits' WZW-type superstring field theory. We construct solutions with parameters out of simpler ones, using a commutative monoid that includes the family of wedge states. Our solutions are generalizations of solutions for marginal deformations by nonsingular currents, and can also reproduce Schnabl's tachyon vacuum solution in bosonic string field theory. This implies that such known solutions are generated from simple solutions which are based on the identity state. We also discuss gauge transformations and induced field redefinitions for our solutions in both bosonic and super string field theory.Comment: 23 pages; v2: PTPTeX, typos correcte

Towards the Ground State of the Supermembrane

The explicit, near the origin, form of the ground state of the SU(2) supermembrane matrix model is studied. We evaluate the 2nd order terms of the Taylor expansion of the wave-function, which together with the 0th and the 1st order terms can be used to determine other terms by recurrence equations coming from the Schroedinger equation.Comment: 17 pages, v2. published in Nucl. Phys.

D0-branes in SO(32)×\timesSO(32) open type 0 string theory

We construct D0-branes in SO(32)$\times$SO(32) open type 0 string theory using the same method as the one used to construct non-BPS D0-brane in type I string theory. It has been proposed that this theory is S-dual to bosonic string theory compactified on SO(32) lattice, which has SO(32)$\times$SO(32) spinor states as excited states of fundamental string. One of these states seems to correspond to the D0-brane, and by the requirement that other states which do not have corresponding states must be removed, we can determine the way of truncation of the spectrum. This result supports the conjecture.Comment: 7 pages, Latex, The description about the truncation is modifie

Comments on D-branes on general group manifolds

We investigate D-branes with maximal symmetry on general group manifolds in terms of boundary states and effective actions. We show that in large $k$ limit boundary states with an suitable Wilson line form boundary states of the other types of D-branes, extending the known fact in SU(2) case. We also show that fluctuation mass spectrum around D-brane solutions of the effective action agrees with that of boundary CFT in large $k$ limit.Comment: LaTeX, 14 pages, no figures v2:minor correction and reference added v3:minor chang