About the measure of the bare cosmological constant

TL;DR

This paper explores the distinction and interplay between the bare cosmological constant and vacuum energy, proposing that primordial gravitational wave signals could help measure the bare Lambda, offering new insights into fundamental cosmological parameters.

Contribution

It suggests a novel approach to constraining the bare cosmological constant through primordial gravitational wave observations, linking established physics with observational cosmology.

Findings

The bare cosmological constant is indirectly constrained by effective cosmological constant measurements.

Fine-tuning of large contributions could be a fundamental property of Nature.

Primordial gravitational waves may provide a way to measure the bare Lambda directly.

Abstract

I try to revive, and possibly reconcile, a debate started a few years ago, about the relative roles of a bare cosmological constant and of a vacuum energy, by taking the attitude to try to get the most from the physics now available as established. I notice that the bare cosmological constant of the Einstein equations, which is there ever since GR emerged, is actually constrained (if not measured) indirectly from the effective cosmological constant observed now, as given by Precision Cosmology and from the cumulative vacuum contribution of Standard Model particles, when this is evaluated using the well-established physics of Quantum Field Theory. Therefore the fine tuning, implied by the compensation to a small positive value of the two large contributions, could be seen as offered by Nature, which provides one more fundamental constant, the bare Lambda. The possibility is then discussed of constraining (measuring) directly such a bare cosmological constant by the features of primordial gravitational wave signals. A hint is briefly discussed for a possible bare Lambda inflation process.