Cosmological variation of the proton-to-electron mass ratio constrained by strong gravitational fields

Exploring the cosmological variations of fundamental dimensionless constants, such as the fine-structure constant, Formula: see text, the proton-to-electron mass ratio, Formula: see text, and the gravitational constant, G, is essential for testing new phenomena beyond the standard cosmological models. This study focuses on investigating the potential variation of constants by analyzing strong gravitational fields associated with white dwarf stars. Utilizing the observed spectrum of G191-B2B, we present a new constraint on the cosmological variation of Formula: see text over extended time scales, Formula: see text, incorporating the gravitational redshift Formula: see text. This finding represents a new tool for checking the parameters for Grand Unified Theories (GUTs).