arXiv subjects

Kazuki Ohmori

Publications and source records attributed to Kazuki Ohmori.

8 recordsLinked to original sources

arXiv2003

Toward Open-Closed String Theoretical Description of Rolling Tachyon

We consider how the time-dependent decay process of an unstable D-brane should be described in the full (quantum) open-closed string theory. It is argued that the system, starting from the unstable D-brane configuration, will evolve in time into the time-independent open string tachyon vacuum configuration which we assume to be finite, with the total energy conserved. As a concrete realization of this idea, we construct a toy model describing the open and closed string tachyons which admits such a time-dependent solution. The structure of our model has some resemblance to that of open-closed string field theory.

hep-th↗

arXiv2003

Level-Expansion Analysis in NS Superstring Field Theory Revisited

We study the level-expansion structure of the NS string field theory actions, mainly focusing on the modified (i.e. 0-picture in the NS sector) cubic superstring field theory. This theory has a non-trivial structure already at the quadratic level due to presence of the picture-changing operator. It is explicitly shown how the usual Maxwell and tachyon actions can be obtained after integrating out the auxiliary fields. We then discuss the reality of the action in the CFT language for all of modified cubic, Witten's cubic and Berkovits' non-polynomial theories. The tachyon condensation problems in modified cubic theory are re-examined. We also carry out level truncation analysis in vacuum superstring field theory proposed in our previous paper, and find some difficulties in both of cubic and non-polynomial formulations.

hep-th↗

arXiv2002

On Ghost Structure of Vacuum Superstring Field Theory

After discussing the general form of the kinetic operator around the tachyon vacuum, we determine the specific form of the pure-ghost kinetic operator Q^ by requiring the twist invariance of the action. We obtain a novel result that the Grassmann-even piece Q_even of Q^ must act differently on GSO(+) sector and on GSO(-) sector to preserve the twist invariance, and show that this structure is crucial for gauge invariance of the action. With this choice of Q^, we construct a solution in an approximation scheme which is conjectured to correspond to a non-BPS D9-brane. We consider both 0-picture cubic and Berkovits' non-polynomial superstring field theories for the NS sector.

hep-th↗

arXiv2002

Comments on Solutions of Vacuum Superstring Field Theory

We study classical solutions of vacuum version of Berkovits' superstring field theory, focusing on the (super)ghost sector. We first argue that the supersliver state which is annihilated by eta_0, though it has the correct quantum numbers and solves the equation of motion, is actually non-perturbatively pure-gauge, and hence it fails to describe a D-brane. As a step toward the construction of non-trivial solutions, we calculate e^{-Phi}Qe^{Phi} for twisted superslivers. As a by-product, we find that the bc-twisted sliver solution in bosonic VSFT can, at least formally, also be written as a pure-gauge configuration.

hep-th↗

arXiv2002

CFT Description of Identity String Field: Toward Derivation of the VSFT Action

We concretely define the identity string field as a surface state and deal with it consistently in terms of conformal field theory language, never using its formal properties nor oscillator representation of it. The generalized gluing and resmoothing theorem provides us with a powerful computational tool which fits into our framework. Among others, we can prove that in some situations the identity state defined this way actually behaves itself like an identity element under the *-product. We use these CFT techniques to give an explicit expression of the classical solution in the ordinary cubic string field theory having the property that the conjectured vacuum string field theory action arises when the cubic action is expanded around it.

hep-th↗

arXiv2001

Survey of the Tachyonic Lump in Bosonic String Field Theory

We study some properties of the tachyonic lumps in the level truncation scheme of bosonic cubic string field theory. We find that several gauges work well and that the size of the lump as well as its tension is approximately independent of these gauge choices at level (2,4). We also examine the fluctuation spectrum around the lump solution, and find that a tachyon with m^2=-0.96 and some massive scalars appear on the lump world-volume. This result strongly supports the conjecture that a codimension 1 lump solution is identified with a D-brane of one lower dimension within the framework of bosonic cubic string field theory.

hep-th↗

arXiv2001

A Review on Tachyon Condensation in Open String Field Theories

We review the recent studies of tachyon condensation in string field theory. After introducing the open string field theory both for bosonic string and for superstring, we use them to examine the conjecture that the unstable configurations of the D-brane will decay into the `closed string vacuum' through the tachyon condensation. And we describe the attemps to construct a lower dimensional bosonic D-brane as an unstable lump solution of the string field equation. We obtain exact results from another formulation, background independent open string field theory. We also discuss some other topics which are related to tachyon condensation in string theory, such as the construction of a D-brane as a noncommutative soliton and some field theory models. This paper is based on my master's thesis submitted to Department of Physics, Faculty of Science, University of Tokyo on January 2001.

hep-th↗

arXiv2001

Tachyonic Kink and Lump-like Solutions in Superstring Field Theory

We construct a kink solution on a non-BPS D-brane using Berkovits' formulation of superstring field theory in the level truncation scheme. The tension of the kink reproduces 95% of the expected BPS D-brane tension. We also find a lump-like solution which is interpreted as a kink--antikink pair, and investigate some of its properties. These results may be considered as successful tests of Berkovits' superstring field theory combined with the modified level truncation scheme.

hep-th↗