Spatial and temporal variations of fundamental constants

TL;DR

This study investigates potential spatial and temporal variations in fundamental constants, using radio astronomical observations and quasar spectra, to test models predicting such variations related to dark energy and scalar fields.

Contribution

It provides new constraints on the variation of the electron-to-proton mass ratio and fine-structure constant in different environments, and reviews existing data on cosmological alpha variation.

Findings

Measured Delta mu/mu = (22 +/- 4_stat +/- 3_sys) x 10^{-9} in low-density environments.

Established an upper limit of |Delta alpha/alpha| < 1.1 x 10^{-7} from astronomical observations.

Found no statistically significant evidence for cosmological variation of alpha at the 10^{-6} level.

Abstract

Spatial and temporal variations in the electron-to-proton mass ratio, mu, and in the fine-structure constant, alpha, are predicted in non-Standard models aimed to explain the nature of dark energy. Among them the so-called chameleon-like scalar field models predict strong dependence of masses and coupling constants on the local matter density. To explore such models we estimated the parameters Delta mu/mu = (mu_obs - mu_lab)/mu_lab and Delta alpha/alpha = (alpha_obs - alpha_lab)/alpha_lab in two essentially different environments, - terrestrial (high density) and interstellar (low density), - from radio astronomical observations of cold prestellar molecular cores in the disk of the Milky Way. We found that Delta mu/mu = (22 +/- 4_stat +/- 3_sys)x10^{-9}, and |Delta alpha/alpha| < 1.1x10^{-7}. If only a conservative upper limit is considered, then |Delta mu/mu| <= 3x10^{-8}. We also reviewed and re-analyzed the available data on the cosmological variation of alpha obtained from FeI and FeII systems in optical spectra of quasars. We show that statistically significant evidence for the changing alpha at the level of 10^{-6} has not been provided so far. The most stringent constraint on |Delta alpha/alpha| < 2x10^{-6} was found from the FeII system at z = 1.15 towards the bright quasar HE0515-4414. The limit of 2x10^{-6} corresponds to the utmost accuracy which can be reached with available to date optical facilities.