On the Evolution of Cosmological Type IA Supernovae and the Gravitational Constant

Abstract

There are at least three ways in which a varying gravitational constant G could affect the interpretation of the recent high-redhisft Type Ia supernovae results. If the local value of G at the space-time location of distant supernovae is different, it would change both the thermonuclear energy release and the time scale of the supernova outburst. In both cases the effect is related to a change in the Chandrasekhar mass M Ch ∝ G −3/2 . Moreover the integrated variation of G with time would also affect cosmic evolution and therefore the luminosity distance relation. Here we investigate in a consistent way how these different effects of a varying G could change the current interpretation of the Hubble diagram of Type Ia supernovae. We parametrize the variation of G using scalar-tensor theories of gravity, such as the Jordan-Brans-Dicke theory or its extensions. It is remarkable that Dirac's hypothesis that G should decrease with time can qualitatively explain the observed ∆m 0.2 mag decrease at z 0.5 (with respect to a decelerating universe) and, at the same time, reduce the duration of the risetimes of distant Type Ia supernovae as recently reported.

Current observational constraints to the holographic dark energy model with a new infrared cutoff via the Markov chain Monte Carlo method

“…which coincides to (A6) up to a constant, is often used in the likelihood analysis [48,50,51], and thus in this case the results will not be affected by a flat M ′ distribution.…”

Observational constraints on holographic dark energy with varying gravitational constant

“…which coincides to (A.4) up to a constant, is often used in the likelihood analysis [33,35,36], and thus in this case the results will not be affected by a flat M ′ distribution.…”

“…Following [33,34], one can obtain the corresponding constraints by fitting the distance modulus µ(z) as…”

Evolving Newton’s constant, extended gravity theories, and SnIa data analysis

“…This evolution induces special effects to the physics of SnIa [15,16,17,18]. The observed magnitude redshift relation of SnIa can be translated to luminosity distance-redshift relation (which leads to the expansion history H(z)) only under the assumption that SnIa behave as standard candles.…”