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Luminosity Evolution of Type 1a Supernovae in R=ct Cosmology

Presentation #312.01 in the session Cosmology II.

Published onJun 29, 2022
Luminosity Evolution of Type 1a Supernovae in R=ct Cosmology

Riess et al. 1998 and Perlmutter et al. 1999 first interpreted the unexpected dimness of the SN1a appearing in the Hubble residuals as evidence for cosmic acceleration by Dark Energy.

Recent investigations (Kelly et al. 2010; Kang et al. 2020; Lee et al. 2020) have found evidence for SN1a Luminosity evolution. This presents a problem for the cosmic acceleration and Dark Energy hypothesis, since the SN1a are assumed to be standard candles and any dimming beyond what is expected must come from another cause.

We present results of a non-accelerating model of the Hubble residual for Type 1a Supernovae (SN1a). Our model adopts a flat FLRW R=ct cosmology as a natural description of our universe (Melia & Shevchuk 2012; Melia 2013). We find that Friedmann’s equation is not satisfied unless the Gravitational constant evolves with redshift, G(z), and the evolving luminosity of SN1a goes as L(z) ~ E(z)3/2 / (1+z)3. Good agreement is found between model predictions of the Hubble residual and observations.

The most important implication of this work is that SN1a luminosity can mimic acceleration in a non-accelerating cosmology. Thus, the unexpected dimness first observed by Riess et al. (1998) & Perlmutter et al. (1999) is fundamentally driven by an evolving Gravitational constant G(z). Finally, the close agreement between the Hubble residual model and observation argues strongly for the form of G(z) derived and suggests that other interesting astrophysics where G is important may require an evolving Gravitational constant.


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