Lucas Lombriser - November 21, 2014

Cosmological and galactic signatures of a universally coupled scalar field

Scalar fields appear in the effective low-energy limit of fundamental theories
of gravity that attempt to unify general relativity with quantum field theory
and may serve as alternative to a cosmological constant driving cosmic
acceleration. In case of nonminimal coupling, the field modifies the
gravitational interactions. These modifications must, however, be suppressed in
the Solar System, where gravity is well tested. Hence, viable scalar-tensor
theories employ screening mechanisms, satisfying local constraints, but leaving
signatures on cosmological and galactic scales. I will discuss predictions from
screening effects on the large-scale structure and constraints that can be
obtained from observations. Then I will show how screening mechanisms can
influence the internal kinematics of dwarf spheroidals in the Milky Way and
cause cuspy matter distributions to appear core-like.