arXiv subjects

Atushi Ishikawa

Publications and source records attributed to Atushi Ishikawa.

25 records · Page 2Linked to original sources

arXiv2000

Splitting of Heterogeneous Boundaries in a System of the Tricritical Ising Model Coupled to 2-Dim Gravity

We study disk amplitudes whose boundaries have heterogeneous matter states in a system of $(4,5)$ conformal matter coupled to 2-dim gravity. They are analysed by using the 3-matrix chain model in the large $N$ limit. Each of the boundaries is composed of two or three parts with distinct matter states. From the obtained amplitudes, it turns out that each heterogeneous boundary loop splits into several loops and we can observe properties in the splitting phenomena that are common to each of them. We also discuss the relation to boundary operators.

hep-th↗

arXiv1997

Interaction of boundaries with heterogeneous matter states in matrix models

We study disk amplitudes whose boundary conditions on matter configurations are not restricted to homogeneous ones. They are examined in the two-matrix model as well as in the three-matrix model for the case of the tricritical Ising model. Comparing these amplitudes, we demonstrate relations between degrees of freedom of matter states in the two models. We also show that they have a simple geometrical interpretation in terms of interactions of the boundaries. It plays an important role that two parts of a boundary with different matter states stick each other. We also find two closed sets of Schwinger-Dyson equations which determine disk amplitudes in the three-matrix model.

hep-th↗

arXiv1997

The Relation between Mixed Boundary States in Two- and Three- Matrix Models

We discuss the relation among some disk amplitudes with non-trivial boundary conditions in two-dimensional quantum gravity. They are obtained by the two-matrix model as well as the three-matirx model for the case of the tricritical Ising model. We examine them for simple spin configurations, and find that a finite number of insertions of the different spin states cannot be observed in the continumm limit. We also find a closed set of eight Schwinger-Dyson equations which determines the disk amplitudes in the three-matrix model.

hep-th↗

arXiv1996

Osp(1|2) Chern-Simons gauge theory as 2D N=1 Induced Supergravity

We demonstrate the close relationship between Chern-Simons gauge theory with gauge group Osp(1|2) and N=1 induced supergravity in two dimensions. More precisely, the inner product of the physical states in the former yields the partition function of the latter evaluated in the Wess-Zumino supergauge. It is also shown that the moduli space of flat Osp(1|2) connections naturally includes super Teichmüller space of super Riemann surfaces.

hep-th↗

arXiv1993

Wheeler-DeWitt Equation in Two-dimensional Quantum Gravity with $c=1$ Conformal Matter Field

In the context of two-dimensional quantum cosmology, we consider the path-integral of a string on annulus which contains the Liouville field and conformal matter fields. We show that, in the transition amplitude of the string universe, the non-zero modes of the fields are all cancelled out only when we take the $c=1$ conformal matter field and impose the Neumann boundary condition on the system. The transition amplitude obtained obeys the minisuperspace Wheeler-DeWitt equation. In our treatment, the modular parameter on annulus plays the role of time variable to integrate out.

hep-th↗

arXiv1993

The Stability of the Minisuperspace

The stability of the minisuperspace model of the early universe is studied by solving the Wheeler-DeWitt equation numerically. We consider a system of Einstein gravity with a scalar field. When we solve the Wheeler-DeWitt equation, we pick up some inhomogeneous wave modes from the infinite number of modes adequately: degrees of freedom of the superspace are restricted to a finite one. We show that the minisuperspace is stable when a scale factor ($a$) of the universe is larger than a few times of the Planck length, while it becomes unstable when $a$ is comparable to the Planck length.

gr-qc↗

arXiv1992

The Wave Function of the Universe by the New Euclidean Path-integral Approach in Quantum Cosmology

The wave function of the universe is evaluated by using the Euclidean path integral approach. As is well known, the real Euclidean path integral diverges because the Einstein-Hilbert action is not positive definite. In order to obtain a finite wave function, we propose a new regularization method and calculate the wave function of the Friedmann- Robertson-Walker type minisuperspace model. We then consider a homogeneous but anisotropic type minisuperspace model, which is known as the Bianch type I model. The physical meaning of the wave function by this new regularization method is also examined.

gr-qc↗