Absence of a fundamental acceleration scale in galaxies
  The Radial Acceleration Relation confirms that a nontrivial acceleration
scale can be found in the average internal dynamics of galaxies. The existence
of such a scale is not obvious as far as the standard cosmological model is
concerned, and it has been interpreted as a possible sign of modified gravity.
The implications could be profound: it could in principle explain galactic
dynamics without large amounts of yet-undetected dark matter and address issues
that the standard cosmological model faces at galactic scales. Here, we
consider 193 disk galaxies from the SPARC and THINGS databases and, using
Bayesian inference, we show that the probability of existence of a fundamental
acceleration that is common to all the galaxies is essentially zero: the
$p$-value is smaller than $10^{-20}$ or, equivalently, the null hypothesis is
rejected at more than 10$\sigma$. We conclude that the acceleration scale
unveiled by the Radial Acceleration Relation is of emergent nature, possibly
caused by a complex interplay between baryons and dark matter. In particular,
the MOND theory, or any other theory that behaves like it at galactic scales,
is ruled out as a fundamental theory for galaxies at more than 10$\sigma$.
