Traversable wormholes from a smoothed string fluid in 4D Einstein-Gauss-Bonnet gravity

TL;DR

This paper demonstrates that in 4D Einstein-Gauss-Bonnet gravity, a smoothed string fluid can support traversable wormholes with regular geometry, satisfying energy conditions and reducing exotic matter through higher-curvature effects.

Contribution

It introduces a novel framework where the same string fluid source can produce both regular black holes and traversable wormholes, influenced by Gauss-Bonnet coupling strength.

Findings

Null energy condition is satisfied near the throat for certain parameters.

Higher Gauss-Bonnet coupling reduces exotic matter and gravitational complexity.

Solutions remain globally regular with finite curvature invariants.

Abstract

We investigate traversable wormhole solutions in four-dimensional Einstein-Gauss-Bonnet (EGB) gravity sourced by a smoothed string fluid. Originally proposed to model regular black holes, this energy density profile is adapted here to sustain wormhole geometries by allowing for a radially varying equation of state. We obtain zero-tidal-force solutions that satisfy all traversability criteria and remain globally regular. The Gauss-Bonnet (GB) coupling $\alpha$ plays a central role in shaping the throat geometry. We identify a parameter region ($\alpha \geq 1$, $\varepsilon \leq 0.1$) in which the null energy condition is satisfied in the vicinity of the throat, representing a significant improvement over general relativistic counterparts. The interplay between the smoothing scale $a$ and the string density $\varepsilon$ ensures finite curvature invariants while reducing the violation of energy conditions. An analysis of the volume integral quantifier and the complexity factor further shows that strong EGB coupling simultaneously suppresses gravitational complexity and the total amount of exotic matter. These results establish a unified framework in which the same string fluid source can generate both regular black holes and stable traversable wormholes, depending on the strength of higher-curvature corrections.