18583938
Boundary state description of tachyon condensation
We construct the explicit boundary state description of the vortex-type (codimension two) tachyon condensation in brane-antibrane systems generalizing the known result of the kink-type (Frau et al. hep-th/9903123). In this description we show how the RR-charge of the lower-dimensional D-branes emerges. We also investigate the tachyon condensation in 4/2 orbifold and find that the twisted sector can be treated almost in the same way as the untwisted sector from the viewpoint of the boundary state. Further we discuss the higher codimension cases.
8088094
D-branes in Melvin background
In this paper we discuss D-branes in the Melvin background and its supersymmetric generalizations. In particular we determine the D-brane spectra in these backgrounds by constructing their boundary states explicitly, where some of the D-branes are supersymmetric. The results sensitively depend on whether the value of magnetic flux in the Melvin background is rational or irrational. For the rational case the D-branes are regarded as the generalizations of fractional D-branes in abelian orbifolds n/N of type-II or type-0 string theory. For the irrational case we found a very limited spectrum. Since the background includes the non-trivial H-flux, the D-branes will provide interesting examples from the viewpoint of the non-commutative geometry.
15121439
Orbifolds as Melvin geometry
In this paper we explicitly show that the various non-compact abelian orbifolds are realized as special limits of parameters in type-II (NSNS) Melvin background and its higher-dimensional generalizations. As a result the supersymmetric ALE spaces (A-type 2/N) and non-supersymmetric orbifolds in type-II and type-0 theory are all connected with each other by the exactly marginal deformation. Our results provide new examples of the duality between type-II and type-0 string theory. We also discuss the decay of unstable backgrounds in this model which include closed string tachyons.
119075487
Worldsheet Description of Tachyon Condensation in Open String Theory
In this thesis we review the fundamental framework of boundary string field theory (BSFT) and apply it to the tachyon condensation on non-BPS systems in the superstring theory. The boundary string field theory can be regarded as a natural extension of the nonlinear sigma model. By using this theory we can describe the tachyon condensation exactly and also obtain the effective actions on non-BPS systems consisting of the Dirac-Born-Infeld type action and the Wess-Zumino type action. Especially the Wess-Zumino action is written by superconnection and coincides with the mathematical argument by K-theory. Moreover we also discuss the tachyon condensation keeping the conformal invariance (on-shell). The exact argument by using the boundary state formalism gives a good support to the conjecture of the tachyon condensation and it is also consistent with boundary string field theory.
15149590
Brane-antibrane action from boundary string field theory
In this paper we give the boundary string field theory description of brane-antibrane systems. From the world-sheet action of brane-antibrane systems we obtain the tachyon potential and discuss the tachyon condensation exactly. We also find the world-volume action including the gauge fields. Moreover we determine RR-couplings exactly for non-BPS branes and brane-antibranes. These couplings are written by superconnections and correspond to K1(M) and K0(M) for the non-BPS branes and brane-antibranes, respectively. We also show that Myers terms appear if we include the transverse scalars in the boundary sigma model action.
123634066
BEAM STUDY OF FFAG ACCELERATOR AT KURRI
In Kyoto University Research Reactor Institute (KURRI), The FFAG accelerator complex for accelerator driven sub-critical reactor (ADSR) project has been already constructed and world first ADSR experiment has been done at March, 2009. In the main ring, proton beams of 11.5MeV are injected and accelerated up to 100MeV. During the acceleration, two different types of beam loss have been observed. To investigate these beam losses, betatron tune and synchrotron oscillation phase have been measured experimentally. The details of measurements will be described in this presentation.
135200451
Beam loading in JHF 50 GeV proton synchrotron