Stabilizing Traversable Wormholes via Quantum Backreaction in Scalar–Gauss–Bonnet Gravity

Traversable wormholes in classical general relativity typically require exotic matter that violates the Null Energy Condition (NEC), making them physically implausible. In contrast, certain modified gravity theories such as scalar–Gauss–Bonnet (sGB) gravity admit wormhole solutions that avoid NEC violation at the classical level. However, the influence of quantum effects on such configurations remains less explored. In this work, we investigate whether quantum backreaction from a conformally coupled scalar field can support a static, spherically symmetric traversable wormhole in sGB gravity without violating the NEC. We adopt a quadratic coupling between the scalar field and the Gauss–Bonnet invariant and compute the renormalized stress-energy tensor using a local curvature expansion in the semiclassical regime. Our results show that the quantum correction contributes positively to the effective energy-momentum tensor. Consequently, the combined classical and quantum stress-energy components satisfy the NEC throughout the spacetime, including at the wormhole throat. This suggests that semiclassical effects can provide a physically consistent mechanism for wormhole stability without requiring exotic matter. Potential observational implications include deviations from standard compact objects or distinctive gravitational lensing signatures.