Testing feasibility of scalar-tensor gravity by scale dependent mass and coupling to matter

TL;DR

This paper explores the potential of a scale-dependent scalar-tensor gravity model to explain astrophysical phenomena without dark matter, fitting galaxy rotation curves and cluster profiles, but faces challenges with supernova data.

Contribution

It introduces a scalar field with a density-dependent mass and coupling, demonstrating its ability to replicate galaxy and cluster observations without dark matter.

Findings

Good fit to low surface brightness galaxy rotation curves using visible matter

Scalar field reproduces cluster mass profiles from X-ray data without dark matter

Difficulty in constraining scale-dependent scalar fields from supernova observations

Abstract

We investigate whether there are any cosmological evidences for a scalar field with a mass and coupling to matter which change accordingly to the properties of the astrophysical system it "lives in", without directly focusing on the underlying mechanism that drives the scalar field scale-dependent properties. We assume a Yukawa type of coupling between the field and matter and also that the scalar field mass grows with density, in order to overcome all gravity constraints within the solar system. We analyse three different gravitational systems assumed as "cosmological indicators": supernovae type Ia, low surface brightness spiral galaxies and clusters of galaxies. Results show that: a) a quite good fit to the rotation curves of low surface brightness galaxies only using visible stellar and gas mass components is obtained; b) a scalar field can fairly well reproduce the matter profile in clusters of galaxies, estimated by X-ray observations and without the need of any additional dark matter; c) there is an intrinsic difficulty in extracting information about the possibility of a scale-dependent massive scalar field (or more generally about a varying gravitational constant) from supernovae type Ia.