Wormhole Solutions and Pre-inflationary Epoch in $F(R,T)$ Gravity with Axion Fields

Abstract

This study investigates axion-dilaton wormhole solutions within the framework of $F(R,T)$ gravity to resolve the issue of insufficient inflationary e-folds in the no-boundary proposal. By examining both Giddings-Strominger and expanding wormhole solutions in asymptotically flat Euclidean spacetime, we demonstrate that the matter-geometry coupling induces complex dynamical oscillations in the scale factor and the dilaton field. These complex oscillatory modes significantly reduce the Euclidean action compared to standard general relativity, consequently enhancing the nucleation probability. Furthermore, we extend this theoretical setup to a ``wineglass'' half-wormhole model in Euclidean Anti-de Sitter (EAdS) spacetime. Our analysis yields a specific constraint on the coupling parameter. This constraint introduces an unstable maximum in the potential and simultaneously decreases the action. The presence of this unstable maximum fundamentally alters the probability distribution of initial states, rendering the evolution of universes from high-potential regions far more probable. Consequently, this approach significantly increases the likelihood of long-lasting inflation, providing a theoretical pathway to reconcile the no-boundary proposal with astronomical observations requiring sustained cosmic expansion.

40 pages, 13 figures

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