# Causal structures and dynamics of black-hole-like solutions in string theory

## TL;DR

This paper explores various spherically symmetric solutions in string theory, revealing complex causal structures, potential firewall scenarios, and implications for black hole information loss, by analyzing parameters like mass, dilaton, and two-form fields.

## Contribution

It provides a detailed classification of black-hole-like solutions in string theory, highlighting how different parameter regimes affect spacetime structure and stability.

## Key findings

- Solutions include singular null hypersurfaces when two-form field is non-zero.
- Near Schwarzschild solutions with altered horizon geometry occur when dilaton and two-form are small.
- Diverging dilaton fields lead to firewall-like or unstable quantum spacetime scenarios.

## Abstract

We investigate spherically symmetric solutions in string theory. Such solutions depend on three parameters, one of which corresponds to the asymptotic mass while the other two are the dilaton and two-form field amplitudes, respectively. If the two-form field amplitude is non-vanishing, then this solution represents a trajectory of a singular and null hypersurface. If the dilaton and two-form field amplitudes are non-vanishing but very close to zero, then the solution is asymptotically the same as the Schwarzschild solution, while only the near horizon geometry will be radically changed. If the dilaton field diverges toward the weak coupling regime, this demonstrates a firewall-like solution. If the dilaton field diverges toward the strong coupling limit, then as we consider quantum effects, this spacetime will emit too strong Hawking radiation to preserve semi-classical spacetime. However, if one considers a junction between the solution and the flat spacetime interior, this can allow a stable star-like solution with reasonable semi-classical properties. We discuss possible implications of these causal structures and connections with the information loss problem.