Jordan-Brans-Dicke Quantum Wormholes and Coleman's Mechanism

TL;DR

This paper explores quantum wormholes in Jordan-Brans-Dicke gravity, demonstrating solutions without matter and showing how Coleman's mechanism favors a universe with a zero cosmological constant and an infinite Brans-Dicke parameter, effectively recovering general relativity.

Contribution

It provides the first analysis of quantum wormholes in Jordan-Brans-Dicke theory and applies Coleman's mechanism to this scalar-tensor framework.

Findings

Quantum wormhole solutions exist without matter in Jordan-Brans-Dicke gravity.

Coleman's mechanism leads to a probability distribution peaked at zero cosmological constant.

The effective low-energy theory aligns with general relativity.

Abstract

We consider the quantum gravity and cosmology of a Jordan-Brans-Dicke theory, predicted by string effective actions. We study its canonical formalism and find that the constraint algebra is that of general relativity, as a consequence of the general covariance of scalar-tensor theories. We also analyze the problem of boundary conditions and propose that they must be imposed in the Jordan frame, in which particles satisfy the strong equivalence principle. Specifically, we discuss both Hartle-Hawking and wormhole boundary conditions in the context of quantum cosmology. We find quantum wormhole solutions for Jordan-Brans-Dicke gravity even in the absence of matter. Wormholes may affect the constants of nature and, in particular, the Brans-Dicke parameter. Following Coleman's mechanism, we find a probability distribution which is strongly peaked at zero cosmological constant and infinite Brans-Dicke parameter. That is, we recover general relativity as the effective low energy theory of gravity.