Entropic constraint on cosmic variation of Planck mass and the Boltzmann constant

Abstract

In cosmology, cosmic variations of fundamental constraints are constrained by the arrow of time of astrophysical black holes, given the Bekenstein–Hawking entropy S∼kBM/mp2 of their event horizon parameterized by black hole mass M and the Planck mass mp=ħc/G, given Planck’s constant ħ, Newton’s constant G, Boltzmann’s constant kB and the velocity of light c. By their large evaporation time of N≃7M⊙/mpM/M⊙3 times the Hubble time, S is effectively non-decreasing with cosmic time by the second law of thermodynamics. It poses a stringent entropic constraint on the evolution of kB and mp with cosmic time, that rules out explaining the JWST “Impossible galaxies” by stretching time in the early Universe. More likely, JWST points to anomalously fast galaxy formation on a conventional matter-dominated cosmological background.

Keywords

• Cosmology – fundamental constants