arXiv subjects

Takesi Saito

Publications and source records attributed to Takesi Saito.

28 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↗

arXiv1998

Grand Unification from Gauge Theory on $M_4 \times Z_N$

The SU(5) grand unified theory (GUT) is derived from the geometrical point of view of gauge theory on three-sheeted space-time, i.e., $M_4 \times Z_3$ manifold without recourse to noncommutative geometry. A derivation of SO(10) GUT is also discussed in the same point of view.

hep-th↗

arXiv1997

Geodesic flows for the Neumann-Rosochatius systems

The Relationship between the Neumann system and the Jacobi system in arbitrary dimensions is elucidated from the point of view of constrained Hamiltonian systems. Dirac brackets for canonical variables of both systems are derived from the constrained Hamiltonians. The geodesic equations corresponding to the Rosochatius system are studied as an application of our method. As a consequence a new class of nonlinear integrable equations is derived along with their conserved quantities.

math-ph↗

arXiv1997

Parallel Transport in Gauge Theory on $M_4 \times Z_2$ Geometry

We apply the gauge theory on $M_4\times Z_2$ geometry previously proposed by Konisi and Saito to the Weinberg-Salam model for electroweak interactions, especially in order to clarify the geometrical meaning of curvatures in this geometry. Considering the Higgs field to be a gauge field along $Z_2$ direction, we also discuss the BRST invariant gauge fixing in this theory.

hep-th↗

arXiv1997

Scalar-Tensor Theory of Gravity on $M_4\times Z_{2}$ Geometry

In the Brans-Dicke(BD) theory on $M_{4}\times Z_{2}$ geometry the geometrical meaning of the torsion is clarified. The BD theory on $M_{4}\times Z_{2}$ is rederived by taking into account of a new isometry condition.

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↗

arXiv1996

$N=2$ and $4$ Super Yang-Mills Theories on $M_4 \times Z_2 \times Z_2$ Geometry

We derive the $N=2$ and $4$ super Yang-Mills theories from the viewpoint of the $M_4\times Z_2\times Z_2$ gauge theory. Scalars and pseudoscalars appearing in the theories are regarded as gauge fields along the directions on $Z_2\times Z_2$ discrete space.

hep-th↗

arXiv1994

Gravity and Discrete Symmetry

Using the differential calculus on discrete group, we study the general relativity in the space-time which is the product of a four dimensional manifold by a two-point space. We generalize the usual concept of frame and connection in our space-time, and from the generalized torsion free condition we obtain an action of a scalar field coupled to Einstein gravity, which may be related to the Jordan-Brans-Dicke theory.

hep-th↗