Gauge Theory and a Dirac Operator on a Noncommutative Space

As a tool to carry out the quantization of gauge theory on a noncommutative space, we present a Dirac operator that behaves as a line element of the canonical noncommutative space. Utilizing this operator, we construct the Dixmier trace, which is the regularized trace for infinite-dimensional matrices. We propose the possibility of solving the cosmological constant problem by applying our gauge theory on the noncommutative space.Comment: 2 figures, final versio

Supersymmetric Field Theories on Noncommutative Spaces

Supersymmetric field theories on noncommutative spaces are constructed. We present two different representations of noncommutative space, but we can obtain supersymmetry algebla and supersymmetric Yang-Mills action independent of its representation. As a result, we will see that the action has a close relationship with IIB matrix model

Unitary-Matrix Integration on 2D Yang-Mills Action

Using the idea of Itzykson-Zuber integral, unitary-matrix integration of 2D Yang-Mills action is presented. The uniqueness of the solution of heat equation enables us to integrate out the unitary-matrix parts of hermite matrices and to obtain the expression of integration over vectors, also in this case.Comment: 8 page

Cyclic Universe \`{a} la string theory

We shall present a model of the "cyclic universe" that can be constructed only by assuming a minimal set of properties of string theory. We clarify our viewpoint of the cyclic universe and show some attempts to mateliarize the idea as field theoretical manner.Comment: Proceeding of International Workshop "Frontier of Quantum Physics" February 17(Thu.)-19(Sat.) 200

Dirac Sea and Hole Theory for Bosons II -- Renormalization Approach --

In bosonic formulation of the negative energy sea, so called Dirac sea presented in the preceding paper [arXiv:hep-th/0603242], one of the crucial points is how to construct a positive definite inner product in the negative energy states, since naive attempts would lead to non-positive definite ones. In the preceding paper the non-local method is used to define the positive definite inner product. In the present article we make use of a kind of $\epsilon$-regularization and renormalization method which may clarify transparently the analytical properties of our formulation.Comment: 10 pages, 2 figures; Section 4 is inserte