What if Newton’s Gravitational Constant Was Negative?

Abstract

In this work, we seek a cosmological mechanism that may define the sign of the effective gravitational coupling constant, G. To this end, we consider general scalar-tensor gravity theories as they provide the field theory natural framework for the variation of the gravitational coupling. We find that models with a quadratic potential naturally stabilize the value of G into the positive branch of the evolution and further, that de Sitter inflation and a relaxation to General Relativity is easily attained.

Non-minimal coupling inspires the Dirac cosmological model

“…Also, emergence of structures in a class of alternative theories of gravity has been reported in [73], where the authors considered a nonminimally coupled scalar field in addition to an induced negative gravitational constant and studied structure formation with repulsive gravitation on the large scale. In the framework of general scalar tensor-theories, a cosmological mechanism has been proposed in which it is possible for G to change sign from a positive branch (attracting) to a negative branch (repulsive gravity) and vice versa [74]. It is also worth mentioning that negative values of G have previously been reported in some other approaches studying the variations of G [16,23,24].…”

A Study in the Variation of <i>G</i>

“…This function can take on negative values before exponentially growing and approaching the horizontal asymptote. This can lead to modeling the universe where there is a transition from a negative to positive Newtonian gravitational parameter which has garnered some interest [31].…”

Scalar-tensor cosmologies in a minisuperspace formulation: a case study

“…We note that the possibility of Φ crossing zero is not analyzed here. It is however possible that dynamically, for certain classes of scalar-tensor theories, the effective gravitational constant becomes negative [72] when appropriate choice of initial conditions is made.…”