scholarly journals Cosmological constraints on matter density perturbations amplitude, neutrino mass and number of relativistic species

2018 ◽  
Vol 191 ◽  
pp. 01009
Author(s):  
Rodion Burenin
Keyword(s):  
Neutrino Mass ◽  
Large Scale ◽  
Hubble Constant ◽  
Density Perturbation ◽  
Matter Density ◽  
Temperature Anisotropy ◽  
Perturbation Amplitude ◽  
High Multipoles ◽  
Density Perturbations ◽  
Cmb Temperature

It is shown that Planck CMB temperature anisotropy data at high multipoles, ℓ > 1000, produce the measurement of matter density perturbations amplitude that contradict to all other constraints obtained both from remaining Planck CMB anisotropy data and from other cosmological data, at about 3:7σ significance level. With the exception of Planck CMB temperature anisotropy data at high multipoles, all other measurements of density perturbation amplitude are in good agreement between each other and give the following measurements of linear density perturbation amplitude: σ8 = 0:792 ± 0:006, mean density of the Universe: Ωm = 0:287 ± 0:007, and Hubble constant: H0 = 69:4 ± 0:6 km s-1 Mpc-1. Therefore, in this case the tensions in H0 constraints between Planck+BAO data and direct H0 measurements are weaken, and the tensions in σ8 measurements between Planck CMB data and large scale structure data disappear completely. Taking in account the data on baryon acoustic oscillations and (or) direct measurements of the Hubble constant, one can obtain different constraints on sum of neutrino mass and number of relativistic species.

scholarly journals The Fractal Turbulence and the Origin of Large Scale Structure

1988 ◽  
Vol 130 ◽  
pp. 553-553
Author(s):  
Y.-Z. Liu ◽  
Z.-G. Deng
Keyword(s):  
Early Universe ◽  
Large Scale ◽  
Hubble Constant ◽  
Large Scale Structure ◽  
Thomson Scattering ◽  
Scale Structure ◽  
Scale Free ◽  
Density Perturbations ◽  
Reynold’S Number ◽  
The Universe

We have suggested a scenario of fractal turbulence which might explain the origin of galaxies and the observed large scale structure of the universe (Liu and Deng, 1987). Under the condition of the early universe, the cosmic fluid can be regarded as incompressible. If we assume that the density perturbations in the early universe are adiabatic and have the scale-free Zeldovich spectrum, we may obtain the spectrum of the velocity perturbations. Perturbations with scales less than horizon will undergo dissipative process by Thomson scattering. So, the cosmic fluid can be considered as a viscous fluid (Peebles, 1971). We can find the largest and smallest scale of the perturbations in the cosmic fluid by taking account of the Reynold's number on given scale and the scale of horizon. Using the present values of Hubble constant and the mean density of matter, we have found that on the scale of horizon the Reynold's number is just the order of 102. This result shows that perturbations with scale a little smaller than horizon may produce Karman vortices before recombination and the vortices might form fractal turbulence due to Thomson drag.

scholarly journals Λ-INFLATION AND CMB ANISOTROPY

2000 ◽  
Vol 15 (24) ◽  
pp. 3783-3804
Author(s):  
V. N. LUKASH ◽  
E. V. MIKHEEVA
Keyword(s):  
Gravitational Waves ◽  
Large Scale ◽  
High Efficiency ◽  
Broad Class ◽  
Power Spectra ◽  
Temperature Anisotropy ◽  
Simple Estimate ◽  
Density Perturbations ◽  
Physical Cosmology ◽  
Hubble Parameters

We explore a broad class of three-parameter inflationary models of the very early Universe, called the Λ-inflation, and its observational predictions: high abundance of cosmic gravitational waves consistent with the Harrison–Zel'dovich spectrum of primordial cosmological perturbations, the non-power-law winglike spectrum of matter density perturbations, and others. High efficiency of these models to meet observational tests is briefly discussed. We show that a parity contribution of the gravitational waves and adiabatic density perturbations into the large-scale temperature anisotropy, T/S~1, is a common feature of Λ-inflation; the maximum values of T/S (basically not larger than 10) are reached in models where (i) the local spectrum shape of density perturbations is flat or slightly red (nS≲1), and (ii) the residual potential energy of the inflaton is near the GUT scale [Formula: see text]. The conditions to get large T/S in the inflationary paradigm and the relation of T/S to the ratio of the power spectra, r, and to the inflationary γ and Hubble parameters, are discussed. We argue that a simple estimate, [Formula: see text], is valid for most known inflationary solutions and allows to relate straightforwardly the important parameters of observational and physical cosmology.

scholarly journals DENSITY PERTURBATIONS, GRAVITY WAVES AND THE COSMIC MICROWAVE BACKGROUND

1992 ◽  
Vol 07 (38) ◽  
pp. 3541-3551 ◽  
Author(s):  
TARUN SOURADEEP ◽  
VARUN SAHNI
Keyword(s):  
Cosmic Microwave Background ◽  
Gravity Waves ◽  
Large Scale ◽  
Cold Dark Matter ◽  
Background Radiation ◽  
Density Perturbation ◽  
Microwave Background ◽  
Relative Contribution ◽  
Microwave Background Radiation ◽  
Density Perturbations

We assess the contribution to the observed large scale anisotropy of the cosmic microwave background radiation, arising from both gravity waves as well as adiabatic density perturbations, generated by a common inflationary mechanism in the early Universe. We find that for inflationary models predicting power law primordial spectra |δk|2∝kn, the relative contribution to the quadrupole anisotropy from gravity waves and scalar density perturbations, depends crucially upon n. For n<0.84, gravity waves perturb the CMBR by a larger amount than density perturbations, whereas for n>0.84 the reverse is true. Normalizing the amplitude of the density perturbation spectrum at large scales, using the observed value of the COBE quadrupole, we determine (δM/M)16-the rms density contrast on scales [Formula: see text] Mpc, for cosmological models with cold dark matter. We find that for n<0.75, a large amount of biasing is required in order to reconcile theory with observations. We also determine the value of the inflationary Hubble parameter and the COBE-normalized amplitude and spectrum of gravity waves from inflation.

scholarly journals Schrödinger–Newton Model with a Background

Symmetry ◽  
2021 ◽  
Vol 13 (6) ◽  
pp. 1007
Author(s):  
José Tito Mendonça
Keyword(s):  
Large Scale ◽  
Laboratory Experiments ◽  
Yukawa Potential ◽  
Matter Density ◽  
Radiation Environment ◽  
Photon Scattering ◽  
Radiation Background ◽  
Quantum Matter ◽  
New Directions ◽  
Density Perturbations

This paper considers the Schrödinger–Newton (SN) equation with a Yukawa potential, introducing the effect of locality. We also include the interaction of the self-gravitating quantum matter with a radiation background, describing the effects due to the environment. Matter and radiation are coupled by photon scattering processes and radiation pressure. We apply this extended SN model to the study of Jeans instability and gravitational collapse. We show that the instability thresholds and growth rates are modified by the presence of an environment. The Yukawa scale length is more relevant for large-scale density perturbations, while the quantum effects become more relevant at small scales. Furthermore, coupling with the radiation environment modifies the character of the instability and leads to the appearance of two distinct instability regimes: one, where both matter and radiation collapse together, and others where regions of larger radiation intensity coincide with regions of lower matter density. This could explain the formation of radiation bubbles and voids of matter. The present work extends the SN model in new directions and could be relevant to astrophysical and cosmological phenomena, as well as to laboratory experiments simulating quantum gravity.

scholarly journals An Accurate Reconstruction of CMB E Mode Signal over Large Angular Scales using Prior Information of CMB Covariance Matrix in ILC Algorithm

2020 ◽  
Author(s):  
Ujjal Purkayastha ◽  
Vipin Sudevan ◽  
Rajib Saha
Keyword(s):  
Power Spectrum ◽  
Linear Combination ◽  
Covariance Matrix ◽  
Large Scale ◽  
Prior Information ◽  
Future Generation ◽  
Temperature Anisotropy ◽  
Satellite Mission ◽  
Angular Power Spectrum ◽  
Accurate Reconstruction

Abstract Recently, the internal-linear-combination (ILC) method was investigated extensively in the context of reconstruction of Cosmic Microwave Background (CMB) temperature anisotropy signal using observations obtained by WMAP and Planck satellite missions. In this article, we, for the first time, apply the ILC method to reconstruct the large scale CMB E mode polarization signal, which could probe the ionization history, using simulated observations of 15 frequency CMB polarization maps of future generation Cosmic Origin Explorer (COrE) satellite mission. We find that the clean power spectra, from the usual ILC, are strongly biased due to non zero CMB-foregrounds chance correlations. In order to address the issues of bias and errors we extend and improve the usual ILC method for CMB E mode reconstruction by incorporating prior information of theoretical E mode angular power spectrum while estimating the weights for linear combination of input maps (Sudevan & Saha 2018b). Using the E mode covariance matrix effectively suppresses the CMB-foreground chance correlation power leading to an accurate reconstruction of cleaned CMB E mode map and its angular power spectrum. We compare the performance of the usual ILC and the new method over large angular scales and show that the later produces significantly statistically improved results than the former. The new E mode CMB angular power spectrum contains neither any significant negative bias at the low multipoles nor any positive foreground bias at relatively higher mutlipoles. The error estimates of the cleaned spectrum agree very well with the cosmic variance induced error.

scholarly journals Anisotropy of the Microwave Background and Biased Galaxy Formation

1988 ◽  
Vol 130 ◽  
pp. 43-50
Author(s):  
Nick Kaiser
Keyword(s):  
Galaxy Formation ◽  
Large Scale ◽  
Microwave Background ◽  
Galaxy Clustering ◽  
Clear View ◽  
Hot Gas ◽  
Density Perturbations ◽  
The Universe ◽  
Theoretical Developments

Fluctuations in the microwave background will have been imprinted at z ≃ 1000, when the photons and the plasma decoupled. On angular scales greater than a few degrees these fluctuations provide a clear view of any primordial density perturbations, and therefore a clean test of theories which invoke such fluctuations from which to form the structure we see in the universe. On smaller angular scales the predictions are less certain: reionization of the gas may modify the spectrum of the primordial fluctuations, and secondary fluctuations may be generated.Here I shall review some recent theoretical developments. A brief survey is made of the currently popular theories for the primordial perturbations, with emphasis on the predictions for large scale anisotropy. One major uncetainty in the predictions arises from the normalisation of the fluctuations to e.g. galaxy clustering, and much attention is given to the question of ‘biased’ galaxy formation. The effect of reionization on the primordial fluctuations is discussed, as is the anisotropy generated from scattering off hot gas in clusters, groups and galaxies.

scholarly journals Decaying Dark Energy in Light of the Latest Cosmological Dataset

Symmetry ◽  
2018 ◽  
Vol 10 (9) ◽  
pp. 372 ◽  
Author(s):  
Ivan de Martino
Keyword(s):  
Dark Energy ◽  
Cosmic Microwave Background ◽  
Parameter Space ◽  
Hubble Constant ◽  
Two Dimensions ◽  
Matter Density ◽  
Microwave Background ◽  
Energy Models ◽  
Cosmic Microwave Background Temperature ◽  
Background Temperature

Decaying Dark Energy models modify the background evolution of the most common observables, such as the Hubble function, the luminosity distance and the Cosmic Microwave Background temperature–redshift scaling relation. We use the most recent observationally-determined datasets, including Supernovae Type Ia and Gamma Ray Bursts data, along with H ( z ) and Cosmic Microwave Background temperature versus z data and the reduced Cosmic Microwave Background parameters, to improve the previous constraints on these models. We perform a Monte Carlo Markov Chain analysis to constrain the parameter space, on the basis of two distinct methods. In view of the first method, the Hubble constant and the matter density are left to vary freely. In this case, our results are compatible with previous analyses associated with decaying Dark Energy models, as well as with the most recent description of the cosmological background. In view of the second method, we set the Hubble constant and the matter density to their best fit values obtained by the Planck satellite, reducing the parameter space to two dimensions, and improving the existent constraints on the model’s parameters. Our results suggest that the accelerated expansion of the Universe is well described by the cosmological constant, and we argue that forthcoming observations will play a determinant role to constrain/rule out decaying Dark Energy.

scholarly journals COSMOLOGICAL CONSTRAINTS FOR THE COSMIC DEFECT THEORY

2011 ◽  
Vol 20 (06) ◽  
pp. 1039-1051 ◽  
Author(s):  
NINFA RADICELLA ◽  
MAURO SERENO ◽  
ANGELO TARTAGLIA
Keyword(s):  
Large Scale ◽  
Hubble Constant ◽  
Big Bang ◽  
Nuclear Species ◽  
Type Ia ◽  
Species Abundances ◽  
Age Of The Universe ◽  
Ia Supernovae ◽  
The Big Bang ◽  
The Universe

The cosmic defect theory has been confronted with four observational constraints: primordial nuclear species abundances emerging from the big bang nucleosynthesis; large scale structure formation in the Universe; cosmic microwave background acoustic scale; luminosity distances of type Ia supernovae. The test has been based on a statistical analysis of the a posteriori probabilities for three parameters of the theory. The result has been quite satisfactory and such that the performance of the theory is not distinguishable from that of the ΛCDM theory. The use of the optimal values of the parameters for the calculation of the Hubble constant and the age of the Universe confirms the compatibility of the cosmic defect approach with observations.

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