Branching Universes

TL;DR

This paper explores a multiverse model where our universe is one of many branches, using modified gravitational wave dispersion relations within a vector field framework, and shows it aligns with current gravitational tests.

Contribution

It introduces a novel multiverse-inspired framework with spatially constrained vector fields that modify gravitational wave behavior without adding new propagating modes.

Findings

Tensor perturbations differ from general relativity

Stealth black hole solutions exist in the theory

Weak gravitational potentials are recovered, passing solar system tests

Abstract

We propose the idea that our Universe is a realization among different possible branches, which can be observationally tested through the modified dispersion relation of the gravitational waves. We achieve this through a framework of spatially constrained vector fields. We show that the simplest realizations of such theories in flat and cosmological spacetimes do not introduce new propagating modes, but they give rise to tensor perturbations that differ from those of standard general relativity. We further show that such theories admit stealth black hole solutions, and we recover weak gravitational potentials, thus passing the solar system experiments. Finally, we discuss the implications of such theories and propose further generalizations.