Phantom Matter and the Cosmological Constant

TL;DR

This paper explores scalar fields with negative kinetic energy in gravity, revealing solutions with continuous matter creation and anti-gravitating behaviors, which could impact models of dark energy and higher-derivative gravity theories.

Contribution

It demonstrates that solutions with negative kinetic energy scalar fields can produce steady states with matter creation and anti-gravity effects, expanding the understanding of dark energy models.

Findings

Solutions with negative kinetic energy scalar fields can mimic cosmological constant effects.

Existence of anti-gravitating solutions that can chase matter or black holes.

Potential applications to gravity theories with higher derivatives.

Abstract

Motivated by some recent speculative attempts to model the dark energy, scalar fields with negative kinetic energy coupled to gravity without a cosmological constant are considered. It is shown that in the presence of an ordinary fluid, any solution of the vacuum Einstein equations with cosmological constant is a solution provided $\rho-P={\Lambda \over 4 \pi G}$. The solutions can be interpreted as a steady state in which matter or entropy is being continuously created (or destroyed). The motion of the matter is not determined by the background Einstein spacetime, many different matter flows can be found giving rise to the same metric. Solutions without ordinary matter are also considered. Anti-gravitating multi-solutions and repulsive solutions which can chase ordinary matter or black holes are exhibited. These results may also have applications to gravity theories with higher derivatives.