Neutron Stars constraints on a late G transition

It has been suggested recently that the Hubble tension could be eliminated by a sharp, ∼ 10 % increase of the effective gravitational constant at z ∼ 0.01 . This would decrease the luminosities of type 1a supernovae in just the needed amount to explain the larger value of the Hubble parameter. In the present paper we call attention to a dramatic effect of such transition on neutron stars. A neutron star that existed at z = 0.01 would contract, conserving the baryon mass but undergoing a mass reduction. We computed neutron star models, with a realistic equation of state, and obtained that this reduction is typically 0.04 M ⊙ . This amounts to an energy of 7 × 10 52 erg. The transition will affect all neutron stars that formed along the history of each galaxy prior to the transition. Given the large number of neutron stars per galaxy, the liberated energy is huge. An estimate of the expected fluxes of neutrinos and x-rays yields values exceeding observational upper limits, thus rendering the late G transition scenario non-viable.