Dark matter candidate induced by Horndeski theory: dark matter halo and cosmological evolution

TL;DR

This paper explores a scalar field within Horndeski theory that behaves as dark matter, explaining galaxy rotation curves and cosmic evolution through a two-fluid model with a pressure-less dark matter component.

Contribution

It introduces a novel scalar field model in Horndeski theory that naturally decomposes into dark matter and dark energy components, with dark matter exhibiting realistic astrophysical behavior.

Findings

Scalar field acts as pressure-less dark matter

Energy density follows inverse-square law

Model explains galaxy rotation curves

Abstract

We study spherically symmetric solutions with a scalar field in the shift-symmetric subclass of the Horndeski theory. Constructing an effective energy-momentum tensor of the scalar field based on the two-fluid model, we decompose the scalar field into two components: dark matter and dark energy.We find the dark-matter fluid is pressure-less, and its distribution of energy density obeys the inverse-square law. We show the scalar field dark matter can explain the galaxy rotation curve and discuss the time evolution of the dark matter in the cosmic background.