M. A. Rodríguez-Meza

Potential–density pairs for spherical galaxies and bulges: the influence of scalar fields

A family of potential-density pairs has been found for spherical haloes and bulges of galaxies in the Newtonian limit of scalar-tensor theories of gravity. The scalar field is described by a Klein-Gordon equation with a source that is coupled to the standard Poisson equation of Newtonian gravity. The net gravitational force is given by two contributions: the standard Newtonian potential plus a term stemming from massive scalar fields. General solutions have been found for spherical systems. In particular, we compute potential-density pairs of spherical, galactic systems, and some other astrophysical quantities that are relevant to generate initial conditions for spherical galaxy simulations.

Spherical scalar-tensor galaxy model

We build a spherical halo model for galaxies using a general scalar-tensor theory of gravity in its Newtonian limit. The scalar field is described by a time-independent Klein-Gordon equation with a source that is coupled to the standard Poisson equation of Newtonian gravity. Our model, by construction, fits both the observed rotation velocities of stars in spirals and a typical luminosity profile. As a result, the form of the new Newtonian potential, the scalar field, and dark matter distribution in a galaxy are determined. Taking into account the constraints for the fundamental parameters of the theory

Potential-density pairs for axisymmetric galaxies: the influence of scalar fields

(\ensuremath{\lambda},\ensuremath{\alpha})

Cosmological simulations using a static scalar-tensor theory

, we analyze the influence of the scalar field in the dark matter distribution, resulting in shallow density profiles in galactic centers.

Flat rotation curves using scalar-tensor theories

We present a formulation for potential–density pairs to describe axi-symmetric galaxies in the Newtonian limit of scalar–tensor theories of gravity. The scalar field is described by a modified Helmholtz equation with a source that is coupled to the standard Poisson equation of Newtonian gravity. The net gravitational force is given by two contributions: the standard Newtonian potential plus a term stemming from massive scalar fields. General solutions have been found for axisymmetric systems and the multipole expansion of the Yukawa potential is given. In particular, we have computed potential–density pairs of galactic disks for an exponential profile and their rotation curves.

Symplectic Symmetry and the Ab Initio No-Core Shell Model

We present ?CDM N-body cosmological simulations in the framework of of a static general scalar-tensor theory of gravity. Due to the influence of the non-minimally coupled scalar field, the gravitational potential is modified by a Yukawa type term, yielding a new structure formation dynamics. We present some preliminary results and, in particular, we compute the density and velocity profiles of the most massive group.

NFW GALACTIC PROFILES IN THE NEWTONIAN LIMIT OF SCALAR–TENSOR THEORIES

We computed flat rotation curves from scalar-tensor theories in their weak field limit. Our model, by construction, fits a flat rotation profile for velocities of stars. As a result, the form of the scalar field potential and DM distribution in a galaxy are determined. By taking into account the constraints for the fundamental parameters of the theory (λ, α), it is possible to obtain analytical results for the density profiles. For positive and negative values of α, the DM matter profile is as cuspy as NFWs.