Verlinde's emergent gravity versus MOND and the case of dwarf
  spheroidals
  In a recent paper, Erik Verlinde has developed the interesting possibility
that spacetime and gravity may emerge from the entangled structure of an
underlying microscopic theory. In this picture, dark matter arises as a
response to the standard model of particle physics from the delocalized degrees
of freedom that build up the dark energy component of the Universe. Dark matter
physics is then regulated by a characteristic acceleration scale $a_0$,
identified with the radius of the (quasi)-de Sitter universe we inhabit. For a
point particle matter source, or outside an extended spherically symmetric
object, MOND's empirical fitting formula is recovered. However, Verlinde's
theory critically departs from MOND when considering the inner structure of
galaxies, differing by a factor of 2 at the centre of a regular massive body.
For illustration, we use the eight classical dwarf spheroidal satellites of the
Milky Way. These objects are perfect testbeds for the model given their
approximate spherical symmetry, measured kinematics, and identified missing
mass. We show that, without the assumption of a maximal deformation, Verlinde's
theory can fit the velocity dispersion profile in dwarf spheroidals with no
further need of an extra dark particle component. If a maximal deformation is
considered, the theory leads to mass-to-light ratios that are marginally larger
than expected from stellar population and formation history studies. We also
compare our results with the recent phenomenological interpolating MOND
function of McGaugh {\it et al}, and find a departure that, for these galaxies,
is consistent with the scatter in current observations.
