Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userCan dark matter-dark energy interaction alleviate the Cosmic Coincidence Problem?
78
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
In this paper we study a model of interacting dark energy - dark matter where the ratio between these components is not constant, changing from early to late times in such a way that the model can solve or alleviate the cosmic coincidence problem (CP). The interaction arises from an assumed relation of the form $rho_xproptorho_d^alpha$, where $rho_x$ and $rho_d$ are the energy densities of dark energy and dark matter components, respectively, and $alpha$ is a free parameter. For a dark energy equation of state parameter $w=-1$ we found that, if $alpha=0$, the standard $Lambda$CDM model is recovered, where the coincidence problem is unsolved. For $0<alpha<1$, the CP would be alleviated and for $alphasim 1$, the CP would be solved. The dark energy component is analyzed with both $w=-1$ and $w eq -1$. Using Supernovae type Ia and Hubble parameter data constraints, in the case $w=-1$ we find $alpha=0.109^{+0.062}_{-0.072}$ at 68% C.L., and the CP is alleviated. This model is also slightly favoured against nonflat $Lambda$CDM model by using a Bayesian Information Criterion (BIC) analysis. For $w eq-1$, a degeneracy arises on the $w$ - $alpha$ plane. In order to break such degeneracy we add cosmic microwave background distance priors and baryonic acoustic oscillations data to the constraints, yielding $alpha=-0.075pm 0.046$ at 68% C.L.. In this case we find that the CP is not alleviated even for 2$sigma$ interval for $alpha$. Furthermore, this last model is discarded against nonflat $Lambda$CDM according to BIC analysis.
rate research
Read More
We consider a dark energy scenario driven by a scalar field $phi$ with a pseudo Nambu Goldstone boson (pNGB) type potential $V(phi)=mu^4 left( 1+ {rm cos}(phi/f) right)$. The pNGB originates out of breaking of spontaneous symmetry at a scale $f$ close to Planck mass $M_{rm{pl}}$. We consider two cases namely the quintessence dark energy and the other, where the standard pNGB action is modified by the terms related to Slotheon cosmology. We demonstrate that for this pNGB potential, high-$f$ problem is better addressed when interaction between dark matter and dark energy is taken into account and that Slotheon dark energy scenario works even better over quintessence in this respect. To this end, a mass limit for dark matter is also estimated.
Recently there has been much interest in light dark matter, especially ultra-light axions, as they may provide a solution to the core-cusp problem at the center of galaxies. Since very light bosons can have a de Broglie wavelength that is of astrophysical size, they can smooth out the centers of galaxies to produce a core, as opposed to vanilla dark matter models, and so it has been suggested that this solves the core-cusp problem. In this work, we critically examine this claim. While an ultra-light particle will indeed lead to a core, we examine whether the relationship between the density of the core and its radius matches the data over a range of galaxies. We first review data that shows the core density of a galaxy $rho_c$ varies as a function of the core radius $R_c$ as $rho_cpropto1/R_c^beta$ with $betaapprox1$. We then compare this to theoretical models. We examine a large class of light scalar dark matter models, governed by some potential $V$. For simplicity, we take the scalar to be complex with a global $U(1)$ symmetry in order to readily organize solutions by a conserved particle number. However, we expect our central conclusions to persist even for a real scalar, and furthermore, a complex scalar matches the behavior of a real scalar in the non-relativistic limit, which is the standard regime of interest. For any potential $V$, we find the relationship between $rho_c$ and $R_c$ for ground state solutions is always in one of the following regimes: (i) $betagg1$, or (ii) $betall1$, or (iii) unstable, and so it never matches the data. We also find similar conclusions for virialized dark matter, more general scalar field theories, degenerate fermion dark matter, superfluid dark matter, and general polytropes. We conclude that the solution to the core-cusp problem is more likely due to either complicated baryonic effects or some other type of dark matter interactions.
We study a class of early dark energy models which has substantial amount of dark energy in the early epoch of the universe. We examine the impact of the early dark energy fluctuations on the growth of structure and the CMB power spectrum in the linear approximation. Furthermore we investigate the influence of the interaction between the early dark energy and the dark matter and its effect on the structure growth and CMB. We finally constrain the early dark energy model parameters and the coupling between dark sectors by confronting to different observations.
We analyze the interaction between Dark Energy and Dark Matter from a thermodynamical perspective. By assuming they have different temperatures, we study the possibility of occurring a decay from Dark Matter into Dark Energy, characterized by a negative parameter $Q$. We find that, if at least one of the fluids has non vanishing chemical potential, for instance $mu_x<0$ and $mu_{dm}=0$ or $mu_x=0$ and $mu_{dm}>0$, the decay is possible, where $mu_x$ and $mu_{dm}$ are the chemical potentials of Dark Energy and Dark Matter, respectively. Using recent cosmological data, we find that, for a fairly simple interaction, the Dark Matter decay is favored with a probability of $sim 93%$ over the Dark Energy decay. This result comes from a likelihood analysis where only background evolution has been considered.
The observation of galaxy and gas distributions, as well as cosmological simulations in a $Lambda$CDM Universe, suggests that clusters of galaxies are still accreting mass and are not expected to be in equilibrium. In this work, we investigate the possibility to evaluate the departure from virial equilibrium in order to detect, in that balance, effects from a Dark Matter--Dark Energy interaction. We continue, from previous works, using a simple model of interacting dark sector, the Layzer--Irvine equation for dynamical virial evolution, and employ optical observations in order to obtain the mass profiles through weak lensing and X-ray observations giving the intracluster gas temperatures. Through a Monte Carlo method, we generate, for a set of clusters, measurements of observed virial ratios, interaction strength, rest virial ratio and departure from equilibrium factors. We found a compounded interaction strength of $-1.99^{+2.56}_{-16.00}$, compatible with no interaction, but also a compounded rest virial ratio of $-0.79 pm 0.13$, which would entail a $2sigma$ detection. We confirm quantitatively that clusters of galaxies are out of equilibrium but further investigation is needed to constrain a possible interaction in the dark sector.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
