Models with a Step-Like Initial Power Spectrum

2006 ◽  
pp. 296-298
Author(s):  
Mirt Gramann ◽  
Gert Hütsi
Keyword(s):  
Power Spectrum ◽  
Initial Power

scholarly journals Thermal Sunyaev–Zel’dovich Effect in the IGM due to Primordial Magnetic Fields

Galaxies ◽  
2018 ◽  
Vol 6 (4) ◽  
pp. 143 ◽  
Author(s):  
Teppei Minoda ◽  
Kenji Hasegawa ◽  
Hiroyuki Tashiro ◽  
Kiyotomo Ichiki ◽  
Naoshi Sugiyama
Keyword(s):  
Magnetic Fields ◽  
Power Spectrum ◽  
Mass Density ◽  
Temperature Anisotropy ◽  
Angular Power Spectrum ◽  
Stringent Constraint ◽  
Small Scales ◽  
Sunyaev Zel'dovich Effect ◽  
Primordial Magnetic Fields ◽  
Initial Power

In the present universe, magnetic fields exist with various strengths and on various scales. One possible origin of these cosmic magnetic fields is the primordial magnetic fields (PMFs) generated in the early universe. PMFs are considered to contribute to matter density evolution via Lorentz force and the thermal history of intergalactic medium (IGM) gas due to ambipolar diffusion. Therefore, information about PMFs should be included in the temperature anisotropy of the Cosmic Microwave Background through the thermal Sunyaev–Zel’dovich (tSZ) effect in IGM. In this article, given an initial power spectrum of PMFs, we show the spatial fluctuation of mass density and temperature of the IGM and tSZ angular power spectrum created by the PMFs. Finally, we find that the tSZ angular power spectrum induced by PMFs becomes significant on small scales, even with PMFs below the observational upper limit. Therefore, we conclude that the measurement of tSZ anisotropy on small scales will provide the most stringent constraint on PMFs.

scholarly journals Modified initial power spectrum and too big to fail problem

2020 ◽  
Vol 494 (4) ◽  
pp. 4907-4913 ◽  
Author(s):  
Hamed Kameli ◽  
Shant Baghram
Keyword(s):  
Dark Matter ◽  
Standard Model ◽  
Power Spectrum ◽  
Initial Conditions ◽  
Dark Matter Halo ◽  
Current Status ◽  
Number Density ◽  
Too Big To Fail ◽  
Standard Case ◽  
Initial Power

ABSTRACT The galactic scale challenges of dark matter such as ‘missing satellite’ problem and ‘too big to fail’ problem are the main caveats of standard model of cosmology. These challenges could be solved either by implementing the complicated baryonic physics or it could be considered as an indication to a new physics beyond the standard model of cosmology. The modification of collisionless dark matter models or the standard initial conditions are two promising venues for study. In this work, we investigate the effects of the deviations from scale invariant initial curvature power spectrum on number density of dark matter haloes. We develop the non-Markov extension of the excursion set theory to calculate the number density of dark matter substructures and dark matter halo progenitor mass distribution. We show that the plausible solution to ‘too big to fail’ problem could be obtained by a Gaussian excess in initial power in the scales of k* ∼ 3 h Mpc−1 that is related to the mass scale of M* ∼ 1011 M⊙. We show that this deviation leads to the decrement of dark matter subhaloes in galactic scale, which is consistent with the current status of the non-linear power spectrum. Our proposal also has a prediction that the number density of Milky Way-type galaxies must be higher than the standard case.

Cosmic Data Fusion

2005 ◽  
Vol 201 ◽  
pp. 368-376
Author(s):  
S. L. Bridle
Keyword(s):  
Power Spectrum ◽  
Large Scale ◽  
Cosmological Parameters ◽  
Big Bang ◽  
Joint Analysis ◽  
Data Sets ◽  
Cluster Number ◽  
Scale Invariant ◽  
Peculiar Velocities ◽  
Initial Power

We compare and combine likelihood functions of the cosmological parameters Ωm, h and σ8 from the CMB, type Ia supernovae and from probes of large scale structure. We include the recent results from the CMB experiments BOOMERANG and MAXIMA-1. Our analysis assumes a flat ACDM cosmology with a scale-invariant adiabatic initial power spectrum. First we consider three data sets that directly probe the mass in the Universe, without the need to relate the galaxy distribution to the underlying mass via a “biasing” relation: peculiar velocities, CMB and supernovae. We assume a baryonic fraction as inferred from Big-Bang Nucleosynthesis and find that all three data sets agree well, overlapping significantly at the 2σ level. This therefore justifies a joint analysis, in which we find a joint best fit point and 95% confidence limits of Ωm = 0.28 (0.17, 0.39), h = 0.74 (0.64, 0.86), and σ8 = 1.17 (0.98,1.37). Secondly we extend our earlier work on combining CMB, supernovae, cluster number counts, IRAS galaxy redshift survey data to include BOOMERANG and MAXIMA-1 data and to allow a free Ωbh2. We find that, given our assumption of a scale invariant initial power spectrum (n = 1), we obtain the robust result of Ωbh2 = 0.031 ± 0.03, which is dominated by the CMB constraint.

scholarly journals Cold versus Warm Dark Matter Simulations of a Galaxy Group

2013 ◽  
Vol 30 ◽  
Author(s):  
Noam I. Libeskind ◽  
Arianna Di Cintio ◽  
Alexander Knebe ◽  
Gustavo Yepes ◽  
Stefan Gottlöber ◽  
...  
Keyword(s):  
Dark Matter ◽  
Power Spectrum ◽  
Cold Dark Matter ◽  
Local Group ◽  
Initial Conditions ◽  
Dark Matter Particle ◽  
Local Environment ◽  
Small Scale ◽  
The Real ◽  
Initial Power

AbstractThe differences between cold dark matter (CDM) and warm dark matter (WDM) in the formation of a group of galaxies are examined by running two identical simulations, where in the WDM case the initial power spectrum has been altered to mimic a 1-keV dark matter particle. The CDM initial conditions were constrained to reproduce at z = 0 the correct local environment within which a ‘Local Group’ (LG) of galaxies may form. Two significant differences between the two simulations are found. While in the CDM case a group of galaxies that resembles the real LG forms, the WDM run fails to reproduce a viable LG, instead forming a diffuse group which is still expanding at z = 0. This is surprising since, due to the suppression of small-scale power in its power spectrum, WDM is naively expected to only affect the collapse of small haloes and not necessarily the dynamics on a scale of a group of galaxies. Furthermore, the concentration of baryons in halo centre is greater in CDM than in WDM and the properties of the discs differ.

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