Keiji Kikkawa

Casimir effects in superstring theories

Abstract Compactification of the space in superstring theories is studied by calculating the one-loop effective potential provided that the supersymmetry is softly broken by some mechanism. The Casimir energy of closed string modes is shown to compactify the ten-dimensional Minkowski space M10 into a stable Md×T10−d(1⩽d a i = α′ R i =1 , where α′ and Ri are the Regge slope and the ith radius of the torus T10−d, respectively. In the SST-I model, although the closed string (gravity) sector decouples from the open string (Yang-Mills) sector in α′ → 0 limit, the former functions as an initiator as well as a stabilizer of the compactification.

Quantum theory of collective motions and an application to theory of extended hadrons

Abstract It is shown that the theory of collective motions can be reduced to a gauge problem in Diracs generalized Hamiltonian formalism. As an example, we study the φ4 theory in two-dimensional space-time by using our formalism.

Gauge invariant values of gluon masses at high temperature

Abstract Both electric and magnetic gluon masses in the high temperature QCD plasma are evaluated up to of order g 3 2 . Gauge covariance is always kept in each step of calculations by taking account of the Ward-Takahashi identity. The magnetic mass is shown to vanish up to O (g 3 2 T) .

Spontaneous compactification in generalized Candelas-Weinberg models

Abstract In their recent work on the dimensional reduction, Candelas and Weinberg considered a model which is compactified into a direct product space of the Minkowski space (M4) and an N-dimensional sphere (SN). In the present paper we investigate generalized models of their type which are compactified into M4 × SM × SN and M4 × SM × CP2. The compactification is caused by the quantum loop effect due to a large number of matter fields. The conditions for the vacuum stability are studied. Numerical computation of the loop effect is undertaken, and it is shown that some of the models of the type M4 × SM × SN admit a stable solution which has finite circumferences of both of the extra spaces and positive coupling constants of the Einstein-Yang-Mills theory in four dimensions.

String field theory in curved space

Abstract The purely cubic action in the string field theory is shown to provide a set of equations of motion for background fields which agree to those obtained by the vanishing condition of s-functions in the non-linear sigma model. Using the sigma model as an auxiliary tool, a systematic method for solving the string field theory in curved space is proposed.

Stability of self-consistent dimensional reduction

Abstract The model of Candelas and Weinberg for the dimensional reduction is generalized and analyzed in detail. Considered here is a system of gravity plus a large number of matter fields compactifying due to quantum loop effects into M 4 × S M × S N , M 4 × CP 2 × S N and variations thereof. Stability conditions of the vacuum are inspected. The positivity of the gauge coupling as well as the gravitational constants is examined. Numerical analysis of the loop effect shows that the model M 4 × S 7 × S 4 admits a stable solution with finite circumferences of both extra spaces.

A possible origin of gauge invariance in low energt physics

Abstract It is pointed out that a part of the gauge invariance in the low energy region, say, lower than the GUT or the Planck energy could be an induced symmetry describable with the Berry phase potential due to partial compactification of a higher dimensional space-time. A model lagrangian with a U (1) gauge symmetry in six dimensions is shown to double the symmetry in four dimensions to enjoy U (1) X U (1) in a limit where the compactification mass scale is sent to infinity. The generalization to non-abelian theories is discussed.

Cancellation of the Lorentz anomaly of string field theory in light-cone gauge

Abstract We study the path-integral measure of string fields in the bosonic open-closed interacting string field theory in light-cone gauge. The Lorentz anomaly of the path-integral measure cancels the Lorentz non-invariant terms of the classical string field action. Thus the theory is shown to be Lorentz invariant at the one-loop level. The one-loop divergent amplitude of the planar open string needs some modified counter-term, which is however not discussed here.

DYNAMICAL GAUGE FIELD INDUCED BY THE BERRY PHASE MECHANISM

Some part of the local gauge symmetries in the low energy region, say, lower than GUT or the Planck energy, can be an induced symmetry that can be described with the holonomy fields associated with a topologically nontrivial structure of partially compactified space. In the case where a six-dimensional space is compactified by the Kaluza-Klein mechanism into a product of the four-dimensional Minkowski space M4 and a two-dimensional Riemann surface with the genus g, Σg, we show that, in a limit where the compactification mass scale is sent to infinity, a model Lagrangian with a U(1) gauge symmetry produces the dynamical gauge fields in M4 with a product of g U(1)s symmetry, i.e. U(1)×···×U(1). These fields are induced by a Berry phase mechanism, not by the Kaluza—Klein mechanism. The dynamical degrees of freedom of the induced fields are shown to come from the holonomies, or the solenoid potentials, associated with the cycles of Σg. The production mechanism of kinetic energy terms for the induced fields i...

Meson mass spectra in the quark-string model

Abstract Old and new meson spectra are studied from a unified view point based on the quark-string lagrangian which has been derived from a continuum limit of the lattice gauge theory. Calculated values for c c states agree with observed values within a few percent error. The ψ → η c γ process is discussed.