Spherically symmetric wormholes in General Relativity and modified gravity with a Kalb-Ramond background

TL;DR

This paper investigates spherically symmetric wormhole solutions supported by the Kalb-Ramond field in General Relativity and modified gravity theories, analyzing their physical properties, stability, and the amount of exotic matter needed.

Contribution

It provides a comprehensive analysis of wormholes sourced by the Kalb-Ramond field in GR, $f(R)$, and $f(R,T)$ gravity, including stability and energy condition evaluations.

Findings

Stable wormholes in GR and $f(R,T)$ gravity.

Unstable wormholes in power-law $f(R)$ gravity.

Reduced exotic matter requirements for certain solutions.

Abstract

Among the several modified/extended gravity paradigms, the concept of antisymmetric connections leading to space-time torsion can be traced back to Cartan. More recently, developments in string theory have suggested the existence of a rank-2 self-interacting tensor field called the Kalb-Ramond field with similar outcomes, the field strength of which can support analytic wormhole-like solutions. However, detailed analyses of the physical properties of interest of such solutions are lacking. In this study, we comprehensively probe the properties of traversable Morris-Thorne like wormhole solutions sourced by the Kalb-Ramond field strength in both General Relativity (GR) and $f(R)$ and $f(R,T)$ modified gravity. We also analyze the coupling of the field strength in GR via a novel non-minimal interaction term in the action. Using suitable parametric constraints in all cases, we evaluate wormhole shape functions, numerically analyze the energy conditions near the throat, check the stability using the generalized Tolman-Oppenheimer-Volkov equation, and demonstrate the possibility of minimum exotic matter by estimating the volume integral quantifier. Our results show the existence of stable wormhole solutions in GR and a simple $f(R,T)$ gravity model, and unstable ones in a power-law type $f(R)$ gravity model.