Juan Magaña

A brief Review of the Scalar Field Dark Matter model

In the last time the cold dark matter (CDM) model has suggested more and more that it is not able to describe all the properties of nearby galaxies that can be observed in great detail as well as that it has some problems in the mechanism by which matter is more rapidly gathered into large-scale structure such as galaxies and clusters of galaxies. In this work we revisit an alternative model, the scalar field dark matter (SFDM) model, which proposes that the galactic haloes form by condensation of a scalar field (SF) very early in the Universe, i.e., in this model the haloes of galaxies are astronomical Bose-Einstein Condensate drops of SF. On the other hand, large-scale structures like clusters or superclusters of galaxies form similar to the ACDM model, by hierarchy, thus all the predictions of the ACDM model at cosmological scales are reproduced by SFDM. This model predicts that all galaxy haloes must be very similar and exist for higher redshifts than in the ACDM model. In the first part of this review we revisit the cosmological evolution of SFDM model with a scalar potential m2Φ2/2 + λΦ4/4 with two different frameworks: the field and fluid approach. We derive the evolution equations of the SF in the linear regime of perturbations as well. The scalar fluctuations have an oscillating growing mode and therefore, this kind of dark matter could lead to the early formation of gravitational structures in the Universe. We also revisit how BEC dark matter haloes exhibit a natural cut of the mass power spectrum. In the second part, we study the core central density profiles of BEC dark matter haloes and fit high-resolution rotation curves, we show a sample of some low surface brightness galaxies. The mean value of the logarithmic inner density slopes is α = −0.27 ± 0.18. Using a model independent new definition of the core in the BEC density profile, we show that the recent observation of the constant dark matter central surface density can be reproduced. We conclude that in light of the difficulties that the ΛCDM model is currently facing the SFDM model can be a worthy alternative to keep exploring further.

Structure formation with scalar field dark matter: the field approach

We study the formation of structure in the Universe assuming that dark matter can be described by a scalar field with a potential V(Φ) = −22/2+λ4/4. We derive the evolution equations of the scalar field in the linear regime of perturbations. We investigate the symmetry breaking and possibly a phase transition of this scalar field in the early Universe. At low temperatures, the scalar perturbations have an oscillating growing mode and therefore, this kind of dark matter could lead to the formation of gravitational structures. In order to study the nonlinear regime, we use the spherical collapse model and show that, in the quadratic potential limit, this kind of dark matter can form virialized structures. The main difference with the traditional Cold Dark Matter paradigm is that the formation of structure in the scalar field model can occur at earlier times. Thus, if the dark matter behaves as a scalar field, large galaxies are expected to be formed already at high redshifts.

On the mass of ultra-light bosonic dark matter from galactic dynamics

We consider the hypothesis that galactic dark matter is composed of ultra-light scalar particles and use internal properties of dwarf spheroidal galaxies to establish a preferred range for the mass m of these bosonic particles. We re-investigate the problem of the longevity of the cold clump in Ursa Minor and the problem of the rapid orbital decay of the globular clusters in Fornax and dwarf ellipticals. Treating the scalar field halo as a rigid background gravitational potential and using N-body simulations, we have explored how the dissolution timescale of the cold clump in Ursa Minor depends on m. It is demonstrated that for masses in the range 0.3 ? 10?22 eV < m < 1 ? 10?22 eV, scalar field dark halos without self-interaction would have cores large enough to explain the longevity of the cold clump in Ursa Minor and the wide distribution of globular clusters in Fornax, but small enough to make the mass of the dark halos compatible with dynamical limits. It is encouraging to see that this interval of m is consistent with that needed to suppress the overproduction of substructure in galactic halos and is compatible with the acoustic peaks of cosmic microwave radiation. On the other hand, for self-interacting scalar fields with coupling constant ?, values of m4/?0.55 ? 103 eV4 are required to account for the properties of the dark halos of these dwarf spheroidal galaxies.

φ2 as dark matter

In this paper we consider

\phi^2 as Dark Matter

\phi^2

ULTRA LIGHT BOSONIC DARK MATTER AND COSMIC MICROWAVE BACKGROUND

scalar field potential as a candidate to dark matter. If it is an ultralight boson particle, it condensates like a Bose-Einstein system at very early times and forms the basic structure of the Universe. Real scalar fields collapse in equilibrium configurations that oscillate in space-time (oscillatons).The cosmological behavior of the field equations are solved using the dynamical system formalism. We use the current cosmological parameters as constraints for the present value of the scalar field. We reproduce the cosmological predictions of the standard

Cosmic slowing down of acceleration for several dark energy parametrizations

\Lambda

On the fraction of dark matter in charged massive particles (CHAMPs)

CDM model with this model. Therefore, scalar field dark matter seems to be a good alternative to cold dark matter nature.

Braneworld model of dark matter: structure formation

In this paper we consider

Testing cosmic acceleration for w(z) parametrizations using fgas measurements in galaxy clusters

\phi^2