Comments on D-Instantons in c<1 Strings

TL;DR

This paper proposes a new interpretation of the boundary cosmological constant in c<1 string theory as a target space coordinate, constructs D-instanton analogues, and demonstrates their effects match known nonperturbative string effects.

Contribution

It introduces a novel geometric viewpoint for boundary cosmological constants and constructs explicit D-instanton analogues in c<1 string theory, linking operator formalism with nonperturbative effects.

Findings

D-instanton effects match exact string solutions

Boundary cosmological constant as target space coordinate

Operator formalism effectively evaluates nonperturbative effects

Abstract

We suggest that the boundary cosmological constant \zeta in c<1 unitary string theory be regarded as the one-dimensional complex coordinate of the target space on which the boundaries of world-sheets can live. From this viewpoint we explicitly construct analogues of D-instantons which satisfy Polchinski's ``combinatorics of boundaries.'' We further show that our operator formalism developed in the preceding articles is powerful in evaluating D-instanton effects, and also demonstrate for simple cases that these effects exactly coincide with the stringy nonperturbative effects found in the exact solutions of string equations.