Stringent null constraint on cosmological evolution of the proton-to-electron mass ratio

TL;DR

This study places a stringent limit on the possible variation of the proton-to-electron mass ratio over cosmic time by analyzing quasar spectra, improving measurement techniques and challenging previous claims of variation.

Contribution

The paper introduces an improved spectral calibration method and absorption profile fitting, providing more accurate constraints on mu variation compared to prior studies.

Findings

No significant variation in mu detected within measurement uncertainty.

Results are inconsistent with previous ~4 sigma claims of mu variation.

Supports the constancy of fundamental constants over cosmological timescales.

Abstract

We present a strong constraint on variation of the proton-to-electron mass ratio, mu, over cosmological time scales using molecular hydrogen transitions in optical quasar spectra. Using high quality spectra of quasars Q0405-443, Q0347-383 and Q0528-250, variation in mu relative to the present day value is limited to (Delta mu)/mu=(2.6 +/- 3.0) x 10^(-6). We reduce systematic errors compared to previous works by substantially improving the spectral wavelength calibration method and by fitting absorption profiles to the forest of hydrogen Lyman alpha transitions surrounding each H_2 transition. Our results are consistent with no variation, and inconsistent with a previous approx 4 sigma detection of mu variation involving Q0405-443 and Q0347-383. If the results of this work and those suggesting that alpha may be varying are both correct, then this would tend to disfavour certain grand unification models.