2 research outputs found
An alternative approach to the galactic dark matter problem
We discuss scenarios in which the galactic dark matter in spiral galaxies is
described by a long range coherent field which settles in a stationary
configuration that might account for the features of the galactic rotation
curves. The simplest possibility is to consider scalar fields, so we discuss in
particular, two mechanisms that would account for the settlement of the scalar
field in a non-trivial configuration in the absence of a direct coupling of the
field with ordinary matter: topological defects, and spontaneous scalarization.Comment: 36 pages, 12 figures, Revtex, a brief discussion added, accepted for
publication in PR
Local Constraints on the Oscillating G Model
We analyze the observational constraints on the effective Brans-Dicke
parameter and on the temporal variation of the effective gravitational constant
within the context of the oscillating G model, a cosmological model based on a
massive scalar field non-minimally coupled to gravity. We show that these local
constraints cannot be satisfied simultaneously once the values of the free
parameters entering the model become fixed by the global attributes of our
Universe. In particular, we show that the lower observational bound for the
effective Brans-Dicke parameter and the upper bound of the variation of the
effective gravitational constant lead to a specific value of the oscillation
amplitude which lies well below the value required to explain the periodicity
of 128 Mpc h^{-1} in the galaxy distribution observed in the pencil beam
surveys.Comment: PRD, subm., 12 pages, 1 figur