The harmonic background paradigm, or why gravity is attractive

TL;DR

This paper introduces the Harmonic Background Paradigm, proposing a fundamental flat spacetime causality to explain why gravity is universally attractive, resolving previous debates on energy conditions and superluminal behavior.

Contribution

It presents a new interpretative framework for gravity, clarifying the relation between energy conditions and causality, and explaining gravity's attractiveness in weak-field regimes.

Findings

The VBL relation explains gravity's attractiveness in weak fields.

The paradigm distinguishes between different interpretative frameworks.

It resolves gauge dependence issues in energy condition relations.

Abstract

In a work by Visser, Bassett and Liberati (VBL) [Nucl. Phys. B (Proc. Suppl.) 88, 267 (2000)] a relation was suggested between a null energy condition and the censorship of superluminal behaviour. Their result was soon challenged by Gao and Wald [Class. Quantum Grav. 17, 4999, (2000)] who argued that this relation is gauge dependent and therefore lacks physical significance. In this paper, we clear up this controversy by showing that both papers are correct but need to be interpreted in distinct paradigms. In this context, we introduce a new paradigm to interpret gravitational phenomena, which we call the Harmonic Background Paradigm. This harmonic background paradigm starts from the idea that there exists a more fundamental background causality provided by a flat spacetime geometry. One of the consequences of this paradigm is that the VBL relation provides an explanation of why gravity is attractive in all standard weak-field situations.