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Akira Kokado

Publications and source records attributed to Akira Kokado.

23 records · Page 2Linked to original sources
arXiv2002

NS Open Strings with B Field and Their Interactions with NS Closed Strings

We consider interactions of a NS open string with first important states of a NS closed string, i.e., a closed-string tachyon and a graviton, where both ends of the NS open string are attached on a D-brane, and a constant background B field is lying along directions parallel to the D-brane world volume. Contrary to general expectations, there are no constraints on these vertex operators coming from the B field. However, we point out that these vertex operators have singularities at both ends of the NS open string when external momenta take some values. These kinds of singularities essentially come from the Dirichlet boundary conditions along directions transverse to the D-brane world volume.

hep-th↗
arXiv2001

Interaction between Noncommutative Open String and Closed-String Tachyon

We construct a vertex operator which describes an emission of the ground-state tachyon of the closed string out of the noncommutative open string. Such a vertex operator is shown to exist only when the momentum of the closed-string tachyon is subject to some constraints coming from the background $B$ field. The vertex operator has a multiplicative coupling constant $g(σ)$ which depends on $σ$ as $g(σ)=\sin^2 σ$ in $0 \le σ\le π$. This behavior is the same as in the ordinary B=0 case.

hep-th↗
arXiv2000

Constrained Quantization of Charged Strings in Background B Field and g-Factors

The Dirac quantization is performed for the constrained system of the open string with different charges located at both ends in the constant background B field. Noncommutativity reveals to commutators [X, X], [P, P] and also [X,P] at both ends of the string. We consider a dependence on the change of the "cyclotron frequency" of the charged string. The g-factor of the charged string is also calculated in the framework of our formulation.

hep-th↗
arXiv1996

Brans-Dicke Theory on $M_4\times Z_2$ Geometry

The gauge theory on $M_4\times Z_2$ geometry is applied to the Brans-Dicke(BD) theory, where $M_4$ is the four dimensional space-time and $Z_2$ is a discrete space with two points. This approach had been previously proposed by Konisi and Saito without recourse to noncommutative geometry(NCG). Since our approach is geometrically simpler and clearer than NCG, one can see more directly the effect of the $Z_2$ space in obtaining the BD theory.

hep-th↗