1 research outputs found
The virial theorem and the dark matter problem in hybrid metric-Palatini gravity
Hybrid metric-Palatini gravity is a recently proposed theory, consisting of
the superposition of the metric Einstein-Hilbert Lagrangian with an
term constructed \`{a} la Palatini. The theory predicts the existence of a
long-range scalar field, which passes the Solar System observational
constraints, even if the scalar field is very light, and modifies the
cosmological and galactic dynamics. Thus, the theory opens new possibilities to
approach, in the same theoretical framework, the problems of both dark energy
and dark matter. In this work, we consider the generalized virial theorem in
the scalar-tensor representation of the hybrid metric-Palatini gravity. More
specifically, taking into account the relativistic collisionless Boltzmann
equation, we show that the supplementary geometric terms in the gravitational
field equations provide an effective contribution to the gravitational
potential energy. We show that the total virial mass is proportional to the
effective mass associated with the new terms generated by the effective scalar
field, and the baryonic mass. This shows that the geometric origin in the
generalized virial theorem may account for the well-known virial theorem mass
discrepancy in clusters of galaxies. In addition to this, we also consider
astrophysical applications of the model and show that the model predicts that
the mass associated to the scalar field and its effects extend beyond the
virial radius of the clusters of galaxies. In the context of the galaxy cluster
velocity dispersion profiles predicted by the hybrid metric-Palatini model, the
generalized virial theorem can be an efficient tool in observationally testing
the viability of this class of generalized gravity models.Comment: 11 pages, no figures; minor modifications, accepted for publication
In JCA