Time-reversed information flow through a wormhole in scalar-tensor gravity

Abstract

This Letter aims to advance unexplored properties of a new class of Closed Timelike Curves recently discovered in scalar-tensor gravity, reported in Universe 9, 467 (2023) and Eur.Phys.J.C 83, 626 (2023). Therein, it was shown that when the Weak Energy Condition is violated, the topology of spacetime in scalar-tensor gravity is altered, enabling the formation of two-way traversable wormholes. Furthermore, each of these wormholes acts a gateway between two $\text{time-mirrored}$ worlds, where the two asymptotically flat sheets in the Kruskal-Szekeres diagram are glued antipodally along $\text{three}$ directions -- time $t$ and the polar and azimuth angles $(\theta ,\phi )$ of the 2-sphere -- to form a wormhole throat. This contrasts with the standard embedding diagram which typically glues the sheets only along the $\theta$ and $\phi$ directions. Crucially, due to the `gluing' along the $t$ direction, the wormhole becomes a portal connecting the two spacetime sheets with $\text{opposite}$ physical time flows, enabling the emergence of closed timelike loops which straddle the throat. We shall point out that this portal $\text{mathematically}$ permits the possibility of backward propagation of information $\text{against}$ time. This feature is ubiquitous for wormholes in scalar-tensor theories. In addition, we formulate the Feynman sum for transition amplitudes of microscopic particles in the proximity of a wormhole throat in which we account for timelike paths that experience time reversal.

arXiv commentTo appear in Phys. Lett. B; 6 pages, 5 figures; slight revisions for clarification, with references added

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