scholarly journals Analytical warm dark matter power spectrum on small scales

2021 ◽  
Vol 2021 (11) ◽  
pp. 062
Author(s):  
G. Pordeus-da-Silva ◽  
R.C. Batista ◽  
L.G. Medeiros
Keyword(s):  
Dark Matter ◽  
Power Spectrum ◽  
Sound Speed ◽  
System Of Equations ◽  
Matter Power Spectrum ◽  
Cosmological Context ◽  
Small Scales ◽  
Analytical Development ◽  
Relativistic Gas ◽  
The Ideal

Abstract Using the Reduced Relativistic Gas (RRG) model, we analytically determine the matter power spectrum for Warm Dark Matter (WDM) on small scales, k > 1 h/Mpc. The RRG is a simplified model for the ideal relativistic gas, but very accurate in the cosmological context. In another work, we have shown that, for typical allowed masses for dark matter particles, m>5 keV, the higher order multipoles, ℓ ≥ 2, in the Einstein-Boltzmann system of equations are negligible on scales k < 10 h/Mpc. Hence, we can follow the perturbations of WDM using the ideal fluid framework, with equation of state and sound speed of perturbations given by the RRG model. We derive a Mészáros-like equation for WDM and solve it analytically in radiation, matter and dark energy dominated eras. Joining these solutions, we get an expression that determines the value of WDM perturbations as a function of redshift and wavenumber. Then we construct the matter power spectrum and transfer function of WDM on small scales and compare it to some results coming from Lyman-α forest observations. Besides being a clear and pedagogical analytical development to understand the evolution of WDM perturbations, our power spectrum results are consistent with the observations considered and the other determinations of the degree of warmness of dark matter particles.

scholarly journals Analytical treatment of small scales matter power spectrum in coupled scalar field (CSF) cosmology

2020 ◽  
Vol 240 ◽  
pp. 02003
Author(s):  
Fargiza A. M. Mulki ◽  
Hesti Wulandari
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Scalar Field ◽  
Power Spectrum ◽  
Cosmological Model ◽  
Baryonic Matter ◽  
Coupling Constant ◽  
Analytical Treatment ◽  
Matter Power Spectrum ◽  
Small Scales

In this paper, we reconstruct matter power spectrum of a cosmological model in which coupled scalar field acts as dark energy. The coupled scalar field (CSF) dark energy we propose here is a generalized model of quintessence, k-essence or phantom coupled to dark matter (non-baryonic matter) via a coupling constant. The existence of coupling between dark energy and matter allows energy to transfer between them, which may give rise to different observational signatures, especially at perturbation level, including matter power spectrum. In this work, through analytical exploration we studied that possible signature in matter power spectrum that maybe induced by this mode.

scholarly journals ETHOS – an effective theory of structure formation: formation of the first haloes and their stars

2019 ◽  
Vol 485 (4) ◽  
pp. 5474-5489 ◽  
Author(s):  
Mark R Lovell ◽  
Jesús Zavala ◽  
Mark Vogelsberger
Keyword(s):  
Dark Matter ◽  
Power Spectrum ◽  
Galaxy Formation ◽  
Cold Dark Matter ◽  
Dwarf Galaxy ◽  
Mass Scale ◽  
Effective Theory ◽  
Matter Power Spectrum ◽  
Hydrodynamical Simulations ◽  
Stellar Masses

Abstract A cut-off in the linear matter power spectrum at dwarf galaxy scales has been shown to affect the abundance, formation mechanism and age of dwarf haloes, and their galaxies at high and low redshifts. We use hydrodynamical simulations of galaxy formation within the ETHOS framework in a benchmark model that has such a cut-off and that has been shown to be an alternative to the cold dark matter (CDM) model that alleviates its dwarf-scale challenges. We show how galaxies in this model form differently to CDM, on a halo-by-halo basis, at redshifts z ≥ 6. We show that when CDM haloes with masses around the ETHOS half-mode mass scale are resimulated with the ETHOS matter power spectrum, they form with 50 per cent less mass than their CDM counterparts due to their later formation times, yet they retain more of their gas reservoir due to the different behaviour of gas and dark matter during the monolithic collapse of the first haloes in models with a galactic-scale cut-off. As a result, galaxies in ETHOS haloes near the cut-off scale grow rapidly between z = 10 and 6 and by z = 6 end up having very similar stellar masses, higher gas fractions and higher star formation rates relative to their CDM counterparts. We highlight these differences by making predictions for how the number of galaxies with old stellar populations is suppressed in ETHOS for both z = 6 galaxies and for gas-poor Local Group fossil galaxies. Interestingly, we find an age gradient in ETHOS between galaxies that form in high- and low-density environments.

scholarly journals Intensity mapping as a probe of axion dark matter

2020 ◽  
Vol 500 (3) ◽  
pp. 3162-3177
Author(s):  
Jurek B Bauer ◽  
David J E Marsh ◽  
Renée Hložek ◽  
Hamsa Padmanabhan ◽  
Alex Laguë
Keyword(s):  
Dark Matter ◽  
Power Spectrum ◽  
Neutral Hydrogen ◽  
Matrix Formalism ◽  
Intensity Mapping ◽  
Matter Power Spectrum ◽  
Wide Range ◽  
Non Linear ◽  
Order Of Magnitude ◽  
Magnitude Improvement

ABSTRACT We consider intensity mapping (IM) of neutral hydrogen (H i) in the redshift range 0 ≲ z ≲ 3 employing a halo model approach where H i is assumed to follow the distribution of dark matter (DM) haloes. If a portion of the DM is composed of ultralight axions, then the abundance of haloes is changed compared to cold DM below the axion Jeans mass. With fixed total H i density, $\Omega _{\rm H\, \rm {\small I}}$, assumed to reside entirely in haloes, this effect introduces a scale-independent increase in the H i power spectrum on scales above the axion Jeans scale, which our model predicts consistent with N-body simulations. Lighter axions introduce a scale-dependent feature even on linear scales due to its suppression of the matter power spectrum near the Jeans scale. We use the Fisher matrix formalism to forecast the ability of future H i surveys to constrain the axion fraction of DM and marginalize over astrophysical and model uncertainties. We find that a HIRAX-like survey is a very reliable IM survey configuration, being affected minimally by uncertainties due to non-linear scales, while the SKA1MID configuration is the most constraining as it is sensitive to non-linear scales. Including non-linear scales and combining a SKA1MID-like IM survey with the Simons Observatory CMB, the benchmark ‘fuzzy DM’ model with ma = 10−22 eV can be constrained at few per cent. This is almost an order of magnitude improvement over current limits from the Ly α forest. For lighter ULAs, this limit improves below 1 per cent, and allows the possibility to test the connection between axion models and the grand unification scale across a wide range of masses.

scholarly journals The halo mass function in alternative dark matter models

2020 ◽  
Vol 493 (1) ◽  
pp. L11-L15 ◽  
Author(s):  
M R Lovell
Keyword(s):  
Dark Matter ◽  
Power Spectrum ◽  
Particle Physics ◽  
Mass Function ◽  
Small Scale ◽  
Acoustic Oscillations ◽  
Sterile Neutrinos ◽  
Matter Power Spectrum ◽  
Alternative Approach ◽  
Good Agreement

ABSTRACT The claimed detection of large amounts of substructure in lensing flux anomalies, and in Milky Way stellar stream gap statistics, has led to a step change in constraints on simple warm dark matter models. In this study, we compute predictions for the halo mass function both for these simple models and for comprehensive particle physics models of sterile neutrinos and dark acoustic oscillations. We show that the mass function fit of Lovell et al. underestimates the number of haloes less massive than the half-mode mass, $M_\mathrm {hm}$, by a factor of 2, relative to the extended Press–Schechter (EPS) method. The alternative approach of applying EPS to the Viel et al. matter power spectrum fit instead suggests good agreement at $M_\mathrm {hm}$ relative to the comprehensive model matter power spectrum results, although the number of haloes with mass $\rm{\lt} M_\mathrm {hm}$ is still suppressed due to the absence of small-scale power in the fitting function. Overall, we find that the number of dark matter haloes with masses $\rm{\lt} 10^{8}{\, \rm M_\odot }$ predicted by competitive particle physics models is underestimated by a factor of ∼2 when applying popular fitting functions, although careful studies that follow the stripping and destruction of subhaloes will be required in order to draw robust conclusions.

scholarly journals Signatures of self-interacting dark matter in the matter power spectrum and the CMB

2018 ◽  
Vol 783 ◽  
pp. 76-81 ◽  
Author(s):  
Ran Huo ◽  
Manoj Kaplinghat ◽  
Zhen Pan ◽  
Hai-Bo Yu
Keyword(s):  
Dark Matter ◽  
Power Spectrum ◽  
Matter Power Spectrum

f(R) COSMOLOGY AND MASSIVE NEUTRINOS

2012 ◽  
Vol 10 ◽  
pp. 35-42 ◽  
Author(s):  
HAYATO MOTOHASHI ◽  
ALEXEI A. STAROBINSKY ◽  
JUN'ICHI YOKOYAMA
Keyword(s):  
Equation Of State ◽  
Power Spectrum ◽  
State Parameter ◽  
Density Fluctuations ◽  
Matter Power Spectrum ◽  
Small Scales ◽  
Λcdm Model ◽  
Equation Of State Parameter ◽  
Massive Neutrinos ◽  
Anomalous Growth

f(R) gravity provides viable cosmology alternative to the ΛCDM model. We discuss the effect of massive neutrinos on matter power spectrum in this theory, to show that the anomalous growth of density fluctuations on small scales due to the scalaron force can be compensated by free streaming of neutrinos. As a result, models which predict observable deviation of the equation-of-state parameter w DE from w DE = -1 may be reconciled with observations of matter clustering if the total neutrino mass is O(0.5 eV ).

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