Speed of sound from fundamental physical constants.

Trachenko, K; Monserrat, B; Pickard, C J; Brazhkin, V V · Sci Adv · 2020

basic_science · Level V

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Abstract

Two dimensionless fundamental physical constants, the fine structure constant α and the proton-to-electron mass ratio [Formula: see text], are attributed a particular importance from the point of view of nuclear synthesis, formation of heavy elements, planets, and life-supporting structures. Here, we show that a combination of these two constants results in a new dimensionless constant that provides the upper bound for the speed of sound in condensed phases, <i>v<sub>u</sub></i> We find that [Formula: see text], where <i>c</i> is the speed of light in vacuum. We support this result by a large set of experimental data and first-principles computations for atomic hydrogen. Our result expands the current understanding of how fundamental constants can impose new bounds on important physical properties.