Closed timelike curves in PT-symmetric wormholes

Abstract: We investigate a modified Einstein-Rosen wormhole model, made unidirectionally traversable through a bimetric geometry defined by two regular metrics, g(+) and g(-), and characterized by PT symmetry combining time reversal (t -> -t) and spatial inversion (x -> -x). In this framework, two distinct spacetime regions are identified at the wormhole throat (r = alpha) via PT symmetry, forming a single spacetime sheet. This model employs Eddington-Finkelstein coordinates to eliminate coordinate singularities at the throat, enabling traversability with a lightlike membrane of exotic matter at the junction to satisfy the Einstein field equations, similar to other traversable wormhole models. We extend this model by coupling two such wormholes to generate closed timelike curves (CTCs), made possible by the opposing causal orientations defined by the two metrics, while adhering to Novikov's self-consistency principle. An effective theory is developed for a scalar field crossing the wormhole, yielding PT-symmetric Klein-Gordon equations with a real energy spectrum ensured by pseudo-unitarity, consistent with quantum mechanical dynamics. These results open new avenues for exploring the effects of PT symmetry on causality and the quantization of scalar fields in traversable geometries.