Two Dimensional Stringy Black Holes with One Asymptotically Flat Domain

TL;DR

This paper studies a 2D string theory black hole with a single asymptotically flat domain obtained via orbifolding, revealing a duality with open string theories and confinement of open string states to the singularity.

Contribution

It introduces a new orbifolded black hole model with one flat domain and explores its physical properties and dualities.

Findings

The orbifold procedure removes the second asymptotic domain.

Open string states are confined to the orbifold singularity.

The model is dual to a conventional open string theory in the black hole background.

Abstract

The exact black hole solution of 2D closed string theory has, as any other maximally extended Schwarzschild-like geometry, two asymptotically flat spacetime domains. One can get rid of the second domain by gauging the discrete symmetry on the SL(2,R)/U(1) coset that interchanges the two asymptotic domains and preserves the Kruskal time orientation everywhere in the Kruskal plane. Here it is shown that upon performing this orbifold procedure, we obtain a theory of unoriented open and closed strings in a black hole background, with just one asymptotically flat domain and a time-like orbifold singularity at the origin. All of the open string states of the model are confined to the orbifold singularity. We also discuss various physical aspects of the truncated black hole, in particular its target duality -- the model is dual to a conventional open string theory in the black hole geometry.