Limits on the space-time variations of fundamental constants

TL;DR

This paper presents improved constraints on the variation of the electron-to-proton mass ratio using radio astronomical observations, achieving the most stringent limits to date on fundamental constant variations.

Contribution

The study introduces new observational data and analysis methods that tighten the bounds on mu variation, surpassing previous limits from radio astronomy.

Findings

Delta mu/mu < 2 x 10^{-8} (3 sigma)

Systematic errors identified in frequency measurements

Most stringent radio astronomical limit on mu variation

Abstract

We report on new tests that improve our previous (2009-2010) estimates of the electron-to-proton mass ratio variation, mu = m_e/m_p. Subsequent observations (2011-2013) at the Effelsberg 100-m telescope of a sample of eight molecular cores from the Milky Way disk reveal systematic errors in the measured sky frequencies varying with an amplitude +/-0.01 km/s during the exposure time. The averaged offset between the radial velocities of the NH3(1,1), HC3N(2-1), HC5N(9-8), HC7N(16-15), HC7N(21-20), and HC7N(23-22) transitions gives Delta V = 0.002 +/- 0.015 km/s [3 sigma confidence level (C.L.)]. This value, when interpreted in terms of Delta mu/mu = (mu_obs - mu_lab)/mu_lab constraints the mu-variation at the level of Delta mu/mu < 2x10^{-8} (3 sigma C.L.), which is the most stringent limit on the fractional changes in mu based on radio astronomical observations.