Scalar field dark matter with a cosh potential, revisited

Abstract

Dark matter models in which the constituent particle is an ultra-light boson have become part of the mainstream discussion in cosmology and astrophysics. At the classical level, the models are represented by the dynamics of a (real or complex) scalar field endowed with a potential that contains its self-interactions, and for this reason are generically known as scalar field dark matter models. Here, we revisit the properties of such a model with a cosh potential and compare it with other known examples in the literature. Within the cosmological context, the self-interaction in the potential induces a radiation-like behavior at early times of the scalar field density, which is followed by a proper matter-like behavior at the onset of rapid field oscillations around the minimum of the potential. The solutions are found by numerical means, and from them we obtain information about the cosmological observables up to the level of linear density perturbations. We also study the general properties of selfgravitating objects in the non-relativistic limit and determine the role in them of the selfinteraction obtained from the cosh potential. An overall conclusion is that, for the range of values in its parameters allowed by different constraints, a cosh potential behaves almost indistinguishable from the simpler quadratic one, which also means that the two models suffer the same tight constraints from cosmological and astrophysical observations.

Generalized tracker quintessence models for dark energy

“…(A1) will only exist for certain combinations of the active parameters α so that the term inside the square brackets is positive definite and 0 < Ω φc < 1. For instance, it can be verified that in the case α 1 = 0 = α 2 we recover the standard expression of the scaling solution reported in the literature: Ω φc = −9γ tot /α 0 , which only exists for potentials with α 0 < 0 [19,20,27,42,43]. However, Eq.…”

“…Also, it must be stressed out that in general the evolution of quintessence density perturbations is driven by the effective wavenumber (7). A related definition of k ef f was firstly presented in [18] for an axion-like potential (for which, in our notation, y 2 = α 0 y, see also [27]), which served to explain the tachyonic instability of scalar field perturbations whenever k 2 ef f < 0. Here, Eq.…”

“…We have revised the case of tracker quintessence models of DE using the same formalism and parametrisation presented before in Refs. [15], but now also including the influence of linear perturbations of the quintessence field following the prescription in [16][17][18]27]. As discussed above, the new formalism allowed the identification of new tracker models which are able to have a behavior more similar to that of the cosmological constant of ΛCDM.…”

Constraints on the mass and self-coupling of Ultra-Light Scalar Field Dark Matter using observational limits on galactic central mass

“…Some recent studies which impose observational constraints on m and λ include [18] (which uses Cosmic Microwave Background anisotropies and large-scale structure data to obtain m > 10 −24 eV and λ < 10 −99 ), [19,20] (which argues for the existence of "minimum DM halo" and uses this to constrain both the mass m, 2.19 × 10 −22 eV < m < 2.92 × 10 −22 eV, and the scattering length, a s = mc λ 32π , for attractive interactions, they obtain −λ ≥ 10 −90 ), [21] (which uses structure formation), [22] (which uses nucleosynthesis constraints on relativistic degrees of freedom), [23] (which uses observed velocity rotation curves to obtain λ ∼ 10 −90 for m ∼ 10 −22 eV).…”

Could galactic magnetic fields be generated by charged ultra-light boson dark matter?

“…It seems that the cosmology is weak sensible to the scalar field potential. The only difference appears in details, like in the cosh potential, where the MPS has a sort of knee in its profile (see [45]). In SFDM, the scalar field at very early stages of the universe remains almost constant until its wave-length was smaller than the size of the horizon, at such point it underwent a phase transition and started to roll down a new minimum where the scalar behaves as dark energy.…”