We report strong cosmological constraints on the Brans-Dicke (BD) theory of gravity using cosmic microwave background data from Planck. We consider two types of models. First, the initial condition of the scalar field is fixed to give the same effective gravitational strength Geff today as the one measured on Earth, GN. In this case, the BD parameter ω is constrained to ω>692 at the 99% confidence level, an order of magnitude improvement over previous constraints. In the second type, the initial condition for the scalar is a free parameter leading to a somewhat stronger constraint of ω>890, while Geff is constrained to 0.981

We derive a general energy balance equation for a self-interacting boson gas at vanishing temperature in a curved spacetime. This represents a first step towards a formulation of the first law of thermodynamics for a scalar field in general relativity. By using a 3 + 1 foliation of the spacetime and performing a Madelung transformation, we rewrite the Klein-Gordon-Maxwell equations in a general curved spacetime into its hydrodynamic version where we can identify the different energy contributions of the system and separate them into kinetic, quantum, electromagnetic, and gravitational.

Density profiles of ultralight Bose-Condensate dark matter inferred from numerical simulations of structure formation, ruled by the Gross-Pitaevskii-Poisson (GPP) system of equations, have a coretail structure. Multi-state equilibrium configurations of the GPP system on the other hand, have a similar core-tail density profile. We now submit these multi-state configurations to highly dynamical scenarios and show their potential as providers of appropriate density profiles of structures. What we do is to present the simulation of head-on collisions between two equilibrium configurations of the GPP system of equations, including the collision of ground state with multi-state configurations. We study the regimes of solitonic and merger behavior, and show generic properties of the dynamics of the system, including the relaxation process and attractor density profiles. We show the merger of multi-state configurations have the potential to produce core-tail density profiles, with the core dominated by the ground state and a halo dominated by an additional states.

Several observations suggest the existence of super-massive black holes (SMBH) at the centers of giant galaxies. However the mechanism under which these objects form remains non completely understood. In this work we review an alternative mechanism of formation of galactic SMBHs. This is, the collapse of ultra-light scalar field configurations playing the role of dark matter halos. Several works have studied this scenario and investigated its plausibility. They demonstrate, by different techniques that a scalar field configuration with masses larger than 0.6 m 2 P l /m φ is able to form a black hole ( configurations made of ultra-light bosons with mass m φ ∼ 10 −22 eV /c 2 has a critical mass of collapse of 10 13 M ). I has been shown that the collapse into a SMBH occurs at a very slow rate, whilst the remaining forms the galactic halo and it is described by quasi-resonant solutions with cosmic lifetime. The theory of collapse of scalar field configurations into compact objects has been extensively studied in a full theoretical way mostly regarding to boson stars. In this work we extrapolate such results for models of galactic halos hosting central SMBHs. We construct the simplest setup of an ultralight scalar field configuration laying in a Schwarzschild space-time for modeling a galactic system with a SMBH in the quasi-static limit. This model is applicable to systems either out of their accretion-phase at late times or either for those undergoing into a very slow accretionphase, such as some early-type giant elliptic galaxies and bulges. On the other hand, very recent direct observation of Sagittarius A by the Event Horizon Telescope Ricarte & Dexter (2015) will open an era of explorations of the deep-inner galactic region of the Milky Way that will possible to test and distinguish various dark matter models. Thus we use our model to give a very first step towards that direction. We derive the stellar kinematics induced by this sort dark matter to obtain information of the black hole's influence into the observable features of the velocity field of visible matter deep inside the galaxy. Thus we compute the radial velocity, acceleration and velocity dispersion densities for some realistic cases.

In this work we study some features of head-on mergers of equilibrium solutions of the Gross-Pitaevskii-Poisson system that rules the dynamics of the ultralight bosonic dark matter model. The importance of equilibrium solutions is that they play the role of halo cores in structure formation simulations. We consider a given range of initial conditions in order to sample the parameter space in terms of mass ratio and head-on momentum. In each case we analyze the relaxation process induced by gravitational cooling in the high and low momentum regimes and estimate the relaxation time scales in each case. We detect a low frequency mode in the whole parameters space and it was found that the resulting configuration oscillates under this mode with amplitude that depends on the mass ratio and head-on momentum. In some cases the resulting configuration oscillates with changes in density of two orders of magnitude and with a matter distribution that is far from isotropic. These results could contribute to the collection of possible mass distributions considered in the reconstruction of mass profiles obtained in structure formation simulations.