Stable soliton dark matter wormhole in non-minimally coupled $f({\cal Q},{\cal T})$ gravity

TL;DR

This paper demonstrates that non-minimal matter-geometry coupling in $f({ m Q},{ m T})$ gravity can produce stable, traversable wormholes without exotic matter, using dark matter density profiles and analyzing their stability.

Contribution

It introduces a novel approach to constructing stable wormholes in modified gravity models with matter-geometry coupling, avoiding the need for exotic matter.

Findings

Wormhole solutions satisfy flaring-out and asymptotic flatness conditions.

NEC can be satisfied at the throat for large positive or negative coupling within bounds.

Stable wormholes are achievable via modified TOV equations considering matter-geometry effects.

Abstract

We show that non-minimal coupling between matter and geometry can indeed help in constructing stable, traversable, wormholes (WHs) without requiring exotic matter under certain conditions. In models like $f({\cal Q},{\cal T})={\cal Q}+\beta {\cal T}$ gravity, where ${\cal Q}$ is the non-metricity scalar, and ${\cal T}$ is the trace of the energy-momentum tensor, the coupling between matter and geometry introduces additional degrees of freedom in terms of the parameter $\beta$. These can mimic the effects of exotic matter or even replace it entirely under specific parameter choice. The analysis involves deriving WH shape functions based on two dark matter (DM) density profiles: a solitonic core at the center of DM halos, and the outer halo follows the universal Navarro-Frenk-White (NFW) density profile of cold DM (CDM). The wormhole solutions derived in these models satisfy important geometric conditions like: Flaring-out condition (necessary for traversability) and asymptotic flatness condition. For large positive coupling parameter, the null energy condition (NEC) can be satisfied at the wormhole throat, meaning exotic matter is not needed, while the wormhole is no longer Lorentzian and the flaring-out condition is broken. However, for large negative coupling parameter, the NEC can be satisfied, allowing for healthy wormholes without exotic matter, provided the coupling strength remains within certain bounds. In the latter case, the NEC is broken only effectively. We investigate the stability of the obtained wormhole solutions by virtue of a modified version of Tolman-Oppenheimer-Volkoff (TOV) equation, which includes a new force due to matter-geometry non-minimal, showing that these wormholes can be dynamically stable.