Effects of Dark Matter on the Spontaneous Scalarization in Neutron Stars

TL;DR

This study explores how dark matter influences spontaneous scalarization in neutron stars, demonstrating that dark matter pressure can either enhance or suppress scalar fields depending on the star's density, with implications for observed neutron star mergers.

Contribution

It introduces the first detailed analysis of dark matter effects on scalarization in neutron stars using observationally motivated dark matter equations of state.

Findings

Dark matter pressure affects scalarization in neutron stars.

Low-density stars show amplified scalar fields with increased dark matter pressure.

High-density stars exhibit suppressed scalar fields due to dark matter pressure.

Abstract

Dark matter, an important portion of compact objects, can influence different phenomena in neutron stars. The spontaneous scalarization in the scalar-tensor gravity has been proposed for neutron stars. Here, we investigate the spontaneous scalarization in dark matter admixed neutron stars. Applying the dark matter equations of state, we calculate the structure of scalarized neutron stars containing dark matter. The dark matter equations of state are based on observational data from the rotational curves of galaxies and the fermionic self-interacting dark matter. Our results verify that the spontaneous scalarization is affected by the dark matter pressure in neutron stars. Depending on the central density of scalarized dark matter admixed neutron stars, the dark matter pressure alters the central scalar field. The increase of dark matter pressure in low-density scalarized stars amplifies the central scalar field. However, the pressure of dark matter in high-density scalarized stars suppresses the central scalar field. Our calculations confirm that the stars in the merger event GW170817 and in the low-mass X-ray binary 4U 1820-30 can be scalarized dark matter admixed neutron stars.