Satoshi Nagaoka

Recombination of intersecting D-branes by local tachyon condensation

We provide a simple low energy description of recombination of intersecting D-branes using super Yang-Mills theory. The recombination is realized by condensation of an off-diagonal tachyonic fluctuation localized at the intersecting point. The recombination process is equivalent to brane-antibrane annihilation, thus our result confirms Sens conjecture on tachyon condensation, although we work in the super Yang-Mills theory whose energy scale is much lower than ?. We also discuss the decay width of non-parallelly separated D-branes.

Realization of brane descent relations in effective theories

We examine Sens descent relations among (non-) Bogomolnyi-Prasad-Sommerfield (BPS) D-branes by using low-energy effective field theories of the

Time evolution viaS-branes

mathrm{D}pmathrm{D}ifmmodebarelsetextasciimacronfi{}p

Graviton propagators on fuzzy G/H

system. We find that the fluctuation around the kink solution reproduces the low-energy matter content on a non-BPS

Fluctuation Analysis of the Non-Abelian Born-Infeld Action in Background Intersecting D-Branes

mathrm{D}(pensuremath{-}1)

Graviton propagators in supergravity and noncommutative gauge theory

-brane. The effective action for these fluctuation modes turns out to be a generalization of the Minahan-Zwiebach model. In addition, it is shown that the fluctuations around the vortex solution consist of massless fields on a BPS

Higher dimensional recombination of intersecting D-branes

mathrm{D}(pensuremath{-}2)

Green-Schwarz superstring from type IIB matrix model

-brane and they are subject to the Dirac-Born-Infeld action. We find the universality that the above results do not refer to particular forms of the effective action.

Superstring vertex operators in type IIB matrix model

Using S(pacelike)-branes defined through rolling tachyon solutions, we show how the dynamical formation of D(irichlet)-branes and strings in tachyon condensation can be understood. Specifically we present solutions of S-brane actions illustrating the classical confinement of electric and magnetic flux into fundamental strings and D-branes. The role of S-branes in string theory is further clarified and their RR charges are discussed. In addition, by examining ``boosted S-branes, we find what appears to be a surprising dual S-brane description of strings and D-branes, which also indicates that the critical electric field can be considered as a self-dual point in string theory. We also introduce new tachyonic S-branes as Euclidean counterparts to non-BPS branes.

String coupling and interactions in type IIB matrix model

We describe closed string modes by open Wilson lines in noncommutative (NC) gauge theories on compact fuzzy G/H in IIB matrix model. In this construction the world sheet cut-off is related to the spacetime cut-off since the string bit of the symmetric traced Wilson line carries the minimum momentum on G/H. We show that the two point correlation functions of graviton type Wilson lines in 4 dimensional NC gauge theories behave as 1/(momentum)2. This result suggests that graviton is localized on D3-brane, so we can naturally interpret D3-branes as our universe. Our result is not limited to D3-brane system, and we generalize our analysis to other dimensions and even to any topology of D-brane worldvolume within fuzzy G/H.