Inflation and Rapid Expansion in a Variable G Model

Abstract

Cosmic inflation is considered assuming a cosmologically varying Newtonian gravitational constant, G. Utilizing two specific models for, G -1 (a), where, a, is the cosmic scale parameter, we find that the Hubble parameter, H , at inception of G -1 , may be as high as 7.56 E53 km/(s Mpc) for model A, or, 8.55 E53 km/(s Mpc) for model B, making these good candidates for inflation. The Hubble parameter is inextricably linked to G by Friedmanns’ equation, and if G did not exist prior to an inception temperature, then neither did expansion. The CBR temperatures at inception of G -1 are estimated to equal, 6.20 E21 Kelvin for model A, and 7.01 E21 for model B, somewhat lower than CBR temperatures usually associated with inflation. These temperatures would fix the size of Lemaitre universe in the vicinity of 3% of the Earths’ radius at the beginning of expansion, thus avoiding a singularity, as is the case in the ΛCDM model. In the later universe, a variable G model cannot be dismissed based on SNIa events. In fact, there is now some compelling astronomical evidence, using rise times and luminosity, which we discuss, where it could be argued that SNIa events can only be used as good standard candles if a variation in G is taken into account. Dark energy may have more to do with a weakening G with increasing cosmological time, versus an unanticipated acceleration of the universe, in the late stage of cosmic evolution.