Visible, invisible and trapped ghosts as sources of wormholes and black universes

TL;DR

This paper constructs explicit, regular solutions in general relativity featuring traversable wormholes and black universes supported by scalar and electromagnetic fields, introducing concepts of trapped and invisible ghosts to reconcile with physical observations.

Contribution

It presents new explicit solutions for regular black holes and wormholes using scalar fields with negative kinetic energy, including the novel ideas of trapped and invisible ghosts.

Findings

Existence of regular black holes and wormholes with various horizon structures.

Introduction of trapped and invisible ghost scalar fields.

Configurations with up to four Killing horizons.

Abstract

We construct explicit examples of globally regular static, spherically symmetric solutions in general relativity with scalar and electromagnetic fields, describing traversable wormholes with flat and AdS asymptotics and regular black holes, in particular, black universes. (A black universe is a regular black hole with an expanding, asymptotically isotropic space-time beyond the horizon.) Such objects exist in the presence of scalar fields with negative kinetic energy ("phantoms", or "ghosts"), which are not observed under usual physical conditions. To account for that, we consider what we call "trapped ghosts" (scalars whose kinetic energy is only negative in a strong-field region of space-time) and "invisible ghosts", i.e., phantom scalar fields sufficiently rapidly decaying in the weak-field region. The resulting configurations contain different numbers of Killing horizons, from zero to four.