Scalar-Tensor Gravity Theory For Dynamical Light Velocity

TL;DR

This paper proposes a scalar-tensor gravity theory where the metric includes a scalar field contribution, potentially explaining cosmic acceleration without dark energy and predicting different propagation speeds for gravitational and non-gravitational waves.

Contribution

It introduces a novel gravity model with a scalar field modifying the metric, offering an alternative explanation for cosmic acceleration without negative pressure or cosmological constant.

Findings

Scalar field contribution can drive universe acceleration

Gravitational waves propagate at different speeds from light

Testable predictions for gravitational wave experiments

Abstract

A gravity theory is developed with the metric ${\hat g}_{\mu\nu}= {g}_{\mu\nu}+B\partial_\mu\phi\partial_\nu\phi$. In the present universe the additional contribution from the scalar field in the metric ${\hat g}_{\mu\nu}$ can generate an acceleration in the expansion of the universe, without negative pressure and with a zero cosmological constant. In this theory, gravitational waves will propagate at a different speed from non-gravitational waves. It is suggested that gravitational wave experiments could test this observational signature.