Regular Instantons in the Eddington-inspired-Born-Infeld Gravity: Lorentzian Wormholes from Bubble Nucleations

TL;DR

This paper investigates regular instanton solutions in EiBI gravity, revealing how large scalar field kinetic energy affects tunneling probabilities and leads to Lorentzian wormhole geometries during bubble nucleation.

Contribution

It introduces new instanton solutions in EiBI gravity and demonstrates the emergence of Lorentzian wormholes from bubble nucleations, highlighting deviations from Einstein gravity.

Findings

Tunneling probability increases with the Born-Infeld coupling constant.

Large scalar field kinetic energy causes deviations from Einstein gravity.

A neck feature indicating Lorentzian wormholes appears in instanton solutions.

Abstract

The O(4)-symmetric regular instanton solutions are studied within the framework of the Eddington-inspired-Born-Infeld gravity (EiBI). We find that the behavior of the solution would deviate from that in Einstein gravity when the kinetic energy of the scalar field is sufficiently large. The tunneling probability is calculated numerically in different parameter space. We find that the tunneling probability would increase with the Born-Infeld coupling constant, which is assumed to be positive in this paper. Furthermore, we discover a neck feature in the physical instanton solutions when the kinetic energy of the scalar field is sufficiently large. This feature can be interpreted as a Lorentzian time-like wormhole geometry formed during the bubble materialization.