Speaker
Description
Cosmological and astronomical observations indicate that the majority
of mass and energy density of fields in the universe are in a form
which interacts extremely weakly, if at all, with light. The standard
interpretation is the existence of dark matter, commonly thought to be
in the form of particles not part of the standard model of particle
physics. At present a firm detection of such a particle is lacking,
and moreover, all these observations concern a mismatch between the
observed dynamics of visible matter with its gravitational influence.
Hence, a less explored interpretation is that the underlying theory of
gravity may not be General Relativity. A hint that this may be the
case is the observation by Milgrom that discrepancies concerning
galaxies are controlled by a single, seemingly universal, acceleration
scale.
In this talk, I will discuss this possibility and focus on a
particular relativistic realization constructed to reproduce Milgrom’s
Modified Newtonian Dynamics law at the scale of galaxies. I will show
that this proposal leads to (i) correct gravitational lensing on
galactic scales, (ii) tensor modes propagating at the speed of light,
and (iii) cosmological evolution in line with observations of the
Cosmic Microwave Background anisotropies and the large-scale structure
power spectrum.
