Analyzing Pantheon SNeIa data in the context of Barrow’s variable speed of light. (arXiv:2010.10292v1 [gr-qc])
<a href="http://arxiv.org/find/gr-qc/1/au:+Nguyen_H/0/1/0/all/0/1">Hoang Nguyen</a>
We analyze the Combined Pantheon Sample of Type Ia supernovae while allowing
the velocity of light to vary as a function of the scale factor $cpropto
a^{-zeta}$, as initiated by Barrow [1]. The variation in the velocity of light
creates an effect akin to the refraction phenomenon which occurs for a wave
traveling in a medium with varying speed of wave. We elucidate the role of the
local scale of gravitationally-bound regions in assisting the refraction effect
to manifest. The refraction effect alters the redshift formulae (Lemaitre,
distance-vs-z, luminosity distance-vs-z) and warrants a new analysis of the
Pantheon dataset. Upon a reformulation of the distance-redshift relations, we
achieve a high-quality fit of the Pantheon dataset to the variable light speed
approach; the fit is as robust as that obtained in the standard $Lambda CDM$
model. We find that the Pantheon dataset is consistent with the variable light
speed of the functional form: $apropto t^{mu}$ and $cpropto a^{1-1/mu}$
with (i) the cosmic age $t_{0}approx 13.9$ Gy as a free parameter, while $mu$
is unspecified; and (ii) a monotonic variation in the local scale for
gravitationally-bound objects (applicable to the emission sources and the Solar
System-based apparatus/observer). Due to the agent in (ii), the high-z portion
of the Pantheon dataset would produce an “effective” $H_{0}$ estimate which is
10 percent lower than the $H_{0}$ estimate obtained from the low-z portion of
the dataset. We offer an alternative interpretation of the accelerating
expansion by way of variable speed of light, and as a by-product of the agent
uncovered in (ii), a tentative suggestion toward “resolving” the ongoing
tension in the Hubble constant estimates.
[1] J.D. Barrow, Cosmologies with Varying Light-Speed, Phys. Rev. D 59,
043515 (1999); arXiv:astro-ph/9811022
We analyze the Combined Pantheon Sample of Type Ia supernovae while allowing
the velocity of light to vary as a function of the scale factor $cpropto
a^{-zeta}$, as initiated by Barrow [1]. The variation in the velocity of light
creates an effect akin to the refraction phenomenon which occurs for a wave
traveling in a medium with varying speed of wave. We elucidate the role of the
local scale of gravitationally-bound regions in assisting the refraction effect
to manifest. The refraction effect alters the redshift formulae (Lemaitre,
distance-vs-z, luminosity distance-vs-z) and warrants a new analysis of the
Pantheon dataset. Upon a reformulation of the distance-redshift relations, we
achieve a high-quality fit of the Pantheon dataset to the variable light speed
approach; the fit is as robust as that obtained in the standard $Lambda CDM$
model. We find that the Pantheon dataset is consistent with the variable light
speed of the functional form: $apropto t^{mu}$ and $cpropto a^{1-1/mu}$
with (i) the cosmic age $t_{0}approx 13.9$ Gy as a free parameter, while $mu$
is unspecified; and (ii) a monotonic variation in the local scale for
gravitationally-bound objects (applicable to the emission sources and the Solar
System-based apparatus/observer). Due to the agent in (ii), the high-z portion
of the Pantheon dataset would produce an “effective” $H_{0}$ estimate which is
10 percent lower than the $H_{0}$ estimate obtained from the low-z portion of
the dataset. We offer an alternative interpretation of the accelerating
expansion by way of variable speed of light, and as a by-product of the agent
uncovered in (ii), a tentative suggestion toward “resolving” the ongoing
tension in the Hubble constant estimates.
[1] J.D. Barrow, Cosmologies with Varying Light-Speed, Phys. Rev. D 59,
043515 (1999); arXiv:astro-ph/9811022
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