Constraints on the electron-to-proton mass ratio variation at the epoch of reionization

TL;DR

This study uses far infrared and rotational transitions of interstellar molecules to set the most stringent constraints on the variation of the electron-to-proton mass ratio mu during the epoch of reionization, suggesting possible dynamical dark energy.

Contribution

It provides the tightest high-redshift limit on mu variation and introduces a regression model describing mu's evolution from recombination to reionization.

Findings

Most stringent limit on Delta mu/mu at z > 6

Regression curve for Delta mu/mu over redshift

Implication for dynamical dark energy

Abstract

Far infrared fine-structure transitions of CI and CII and rotational transitions of CO are used to probe hypothetical variations of the electron-to-proton mass ratio mu = m_e/m_p at the epoch of reionization (z > 6). A constraint on Delta mu/mu = (mu_obs - mu_lab)/mu_lab = (0.7 +/- 1.2)x10^-5 (1sigma) obtained at <z> = 6.31 is the most stringent up-to-date limit on the variation of mu at such high redshift. For all available estimates of Delta mu/mu ranging between z = 0 and z = 1100, - the epoch of recombination, - a regression curve Delta mu/mu = k_mu (1+z)^p, with k_mu = (1.6 +/- 0.3) x10^-8 and p = 2.00 +/- 0.03, is deduced. If confirmed, this would imply a dynamical nature of dark matter/dark energy.