Model-independent confirmation of a constant speed of light over cosmological distances. (arXiv:2312.09458v1 [astro-ph.CO])
<a href="http://arxiv.org/find/astro-ph/1/au:+Melia_F/0/1/0/all/0/1">Fulvio Melia</a>
Recent attempts at measuring the variation of $c$ using an assortment of
standard candles and the redshift-dependent Hubble expansion rate inferred from
the currently available catalog of cosmic chronometers have tended to show that
the speed of light appears to be constant, at least up to $zsim 2$. A notable
exception is the use of high-redshift UV $+$ X-ray quasars, whose Hubble
diagram seems to indicate a $sim 2.7sigma$ deviation of c from its value
$c_0$ ($equiv 2.99792458 times 10^{10}$ cm s$^{-1}$) on Earth. We show in
this paper, however, that this anomaly is due to an error in the derived
relation between the luminosity distance, $D_L$, and $H(z)$ when $c$ is allowed
to vary with redshift, and an imprecise calibration of the quasar catalog. When
these deficiences are addressed correctly, one finds that $c/c_0=0.95 pm 0.14$
in the redshift range $0lesssim zlesssim 2$, fully consistent with zero
variation within the measurement errors.
Recent attempts at measuring the variation of $c$ using an assortment of
standard candles and the redshift-dependent Hubble expansion rate inferred from
the currently available catalog of cosmic chronometers have tended to show that
the speed of light appears to be constant, at least up to $zsim 2$. A notable
exception is the use of high-redshift UV $+$ X-ray quasars, whose Hubble
diagram seems to indicate a $sim 2.7sigma$ deviation of c from its value
$c_0$ ($equiv 2.99792458 times 10^{10}$ cm s$^{-1}$) on Earth. We show in
this paper, however, that this anomaly is due to an error in the derived
relation between the luminosity distance, $D_L$, and $H(z)$ when $c$ is allowed
to vary with redshift, and an imprecise calibration of the quasar catalog. When
these deficiences are addressed correctly, one finds that $c/c_0=0.95 pm 0.14$
in the redshift range $0lesssim zlesssim 2$, fully consistent with zero
variation within the measurement errors.
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