Hartle-Hawking no-boundary proposal in dRGT massive gravity: Making inflation exponentially more probable

TL;DR

This paper demonstrates that in dRGT massive gravity, the probability of inflation with many e-folds can be exponentially increased, making inflation more likely in quantum cosmology models.

Contribution

It shows that the massive gravity sector can significantly enhance inflation probability, especially with a large mass parameter, offering new insights into quantum cosmology.

Findings

Massive gravity can boost inflation probability exponentially.

Large mass parameter $m_g geq 10^{12}$ GeV enhances inflation likelihood.

Models can be constructed with large early-universe mass and small present-day mass.

Abstract

It is known that the no-boundary proposal in the traditional Einstein gravity does not prefer inflation, that is, the probability of realizing a large number of e-folds is exponentially suppressed. This situation may be changed drastically in a class of nonlinear massive gravity theories recently proposed by deRham, Gabadadze and Tolley, called dRGT massive gravity. We show that the contribution from the massive gravity sector can enhance the probability of a large number of e-folds substantially for a sufficiently large mass parameter mg comparable to the Hubble parameter during inflation, say $m_g \gtrsim 10^{12}$ GeV. We illustrate possible models to trigger such a large mass parameter in the early universe while it is negligibly small in the present universe. This opens a new window to explore the inflationary scenario in the context of quantum cosmology.