Yukio Kikuchi

Heterotic string modifications of Einstein's and Yang-Mills' actions

Abstract We derive the quartic curvature and quartic gauge field modifications to the low-energy effective action in the heterotic string theory by studying tree level four-point scattering amplitudes. The results provide further constraints on compactification of the ten-dimensional spacetime; in particular, it appears that Calabi-Yau manifolds do not provide consistent compactification of the heterotic string.

Modular invariance in closed superstrings

Abstract Previous explicit results for open superstrings are employed to prove modular invariance and hence finiteness of the pentagon diagram (probably extensible to higher-point one-loop diagrams) in several closed superstring theories: type II, the heterotic string, and the generalizations of the heterotic string due to Narain.

One Parameter Extension of SU(3) Kac-Moody Algebra and Screening Currents

It is known that free-field realization of Kac-Moody algebra is not unique. By taking the explicit example of one parameter extension of SU (3), that is, the generalization of the well-known Wakimoto representation, we make some remarks on the relation between Kac-Moody currents and screening currents. Corresponding SU (3) parafermions are also considered. A general procedure is outlined to obtain the general parameter extension of the Wakimoto representation of KM algebras with free fields.

COVARIANT DERIVATIVE EXPANSION FOR NON-LINEAR σ-MODEL WITH TWO MULTIPLETS

The covariant derivative expansion is generalized to the case of two multiplets in the non-linear σ-model.

Dimensional reduction through generalized OSp-symmetry and higher-derivative theories

Abstract The generalized OSp-invariant model in the extended superspace is formulated. A remarkable relation is pointed out between some higher-derivative theories and corresponding theories in the lower-dimensional ordinary space-time.