scholarly journals The matter fluctuation amplitude inferred from the weak lensing power spectrum and correlation function in CFHTLenS data

2019 ◽  
Vol 490 (4) ◽  
pp. 5033-5042
Author(s):  
Tianhuan Lu ◽  
Zoltán Haiman
Keyword(s):  
Correlation Function ◽  
Power Spectrum ◽  
Systematic Errors ◽  
Small Scale ◽  
Microwave Background ◽  
Planck Data ◽  
Point Correlation ◽  
Point Correlation Function ◽  
Fluctuation Amplitude ◽  
Excess Power

ABSTRACT Based on the cosmic shear data from the Canada–France–Hawaii Telescope Lensing Survey (CFHTLenS), Kilbinger et al. obtained a constraint on the amplitude of matter fluctuations of σ8(Ωm/0.27)0.6 = 0.79 ± 0.03 from the two-point correlation function (2PCF). This is ≈3σ lower than the value 0.89 ± 0.01 derived from Planck data on cosmic microwave background (CMB) anisotropies. On the other hand, based on the same CFHTLenS data, but using the power spectrum, and performing a different analysis, Liu et al. obtained the higher value of $\sigma _8(\Omega _\mathrm{m}/0.27)^{0.64}=0.87^{+0.05}_{-0.06}$. We here investigate the origin of this difference, by performing a fair side-by-side comparison of the 2PCF and power spectrum analyses on CFHTLenS data. We find that these two statistics indeed deliver different results, even when applied to the same data in an otherwise identical procedure. We identify excess power in the data on small scales (ℓ > 5000) driving the larger values inferred from the power spectrum. We speculate on the possible origin of this excess small-scale power. More generally, our results highlight the utility of analysing the 2PCF and the power spectrum in tandem, to discover (and to help control) systematic errors.

scholarly journals Cosmological Spectrum of Two-Point Correlation Function from Vacuum Fluctuation of Stringy Axion Field in De Sitter Space: A Study of the Role of Quantum Entanglement

Universe ◽  
2020 ◽  
Vol 6 (6) ◽  
pp. 79
Author(s):  
Sayantan Choudhury ◽  
Sudhakar Panda
Keyword(s):  
Correlation Function ◽  
Power Spectrum ◽  
Quantum Entanglement ◽  
De Sitter Space ◽  
Entangled State ◽  
De Sitter ◽  
Vacuum Fluctuation ◽  
Axion Field ◽  
Point Correlation ◽  
Point Correlation Function

In this work, we study the impact of quantum entanglement on the two-point correlation function and the associated primordial power spectrum of mean square vacuum fluctuation in a bipartite quantum field theoretic system. The field theory that we consider is the effective theory of axion field arising from Type IIB string theory compacted to four dimensions. We compute the expression for the power spectrum of vacuum fluctuation in three different approaches, namely (1) field operator expansion (FOE) technique with the quantum entangled state, (2) reduced density matrix (RDM) formalism with mixed quantum state and (3) the method of non-entangled state (NES). For a massless axion field, in all three formalisms, we reproduce, at the leading order, the exact scale invariant power spectrum which is well known in the literature. We observe that due to quantum entanglement, the sub-leading terms for these thee formalisms are different. Thus, such correction terms break the degeneracy among the analysis of the FOE, RDM and NES formalisms in the super-horizon limit. On the other hand, for massive axion field we get a slight deviation from scale invariance and exactly quantify the spectral tilt of the power spectrum in small scales. Apart from that, for massless and massive axion field, we find distinguishable features of the power spectrum for the FOE, RDM, and NES on the large scales, which is the result of quantum entanglement. We also find that such large-scale effects are comparable to or greater than the curvature radius of the de Sitter space. Most importantly, in near future if experiments probe for early universe phenomena, one can detect such small quantum effects. In such a scenario, it is possible to test the implications of quantum entanglement in primordial cosmology.

scholarly journals Validating the methodology for constraining the linear growth rate from clustering anisotropies

2020 ◽  
Vol 494 (2) ◽  
pp. 1658-1674
Author(s):  
Jorge Enrique García-Farieta ◽  
Federico Marulli ◽  
Lauro Moscardini ◽  
Alfonso Veropalumbo ◽  
Rigoberto A Casas-Miranda
Keyword(s):  
Growth Rate ◽  
Correlation Function ◽  
Measurement Errors ◽  
Linear Growth ◽  
Dispersion Model ◽  
Linear Growth Rate ◽  
Small Scale ◽  
Point Correlation ◽  
Point Correlation Function ◽  
The Impact

ABSTRACT Redshift-space clustering distortions provide one of the most powerful probes to test the gravity theory on the largest cosmological scales. We perform a systematic validation study of the state-of-the-art statistical methods currently used to constrain the linear growth rate from redshift-space distortions in the galaxy two-point correlation function. The numerical pipelines are tested on mock halo catalogues extracted from large N-body simulations of the standard cosmological framework. We consider both the monopole and quadrupole multipole moments of the redshift-space two-point correlation function, as well as the radial and transverse clustering wedges, in the comoving scale range 10 < r[$h^{-1}\, \mbox{Mpc}$] < 55. Moreover, we investigate the impact of redshift measurement errors on the growth rate and linear bias measurements due to the assumptions in the redshift-space distortion model. Considering both the dispersion model and two widely used models based on perturbation theory, we find that the linear growth rate is underestimated by about $5\!-\! 10\, {\rm {per\ cent}}$ at $z$ < 1, while limiting the analysis at larger scales, r > 30 $h^{-1}\, \mbox{Mpc}$, the discrepancy is reduced below $5\, {\rm {per\ cent}}$. At higher redshifts, we find instead an overall good agreement between measurements and model predictions. Though this accuracy is good enough for clustering analyses in current redshift surveys, the models have to be further improved not to introduce significant systematics in RSD constraints from next-generation galaxy surveys. The effect of redshift errors is degenerate with the one of small-scale random motions, and can be marginalized over in the statistical analysis, not introducing any statistically significant bias in the linear growth constraints, especially at $z$ ≥ 1.

scholarly journals Matter power spectrum: from Ly α forest to CMB scales

2019 ◽  
Vol 489 (2) ◽  
pp. 2247-2253 ◽  
Author(s):  
Solène Chabanier ◽  
Marius Millea ◽  
Nathalie Palanque-Delabrouille
Keyword(s):  
Power Spectrum ◽  
Power Spectra ◽  
Model Fit ◽  
Microwave Background ◽  
Luminous Red Galaxies ◽  
Matter Power Spectrum ◽  
Physical Scale ◽  
Point Correlation ◽  
Point Correlation Function ◽  
Red Galaxies

ABSTRACT We present a new compilation of inferences of the linear 3D matter power spectrum at redshift $z\, {=}\, 0$ from a variety of probes spanning several orders of magnitude in physical scale and in cosmic history. We develop a new lower noise method for performing this inference from the latest Ly α forest 1D power spectrum data. We also include cosmic microwave background (CMB) temperature and polarization power spectra and lensing reconstruction data, the cosmic shear two-point correlation function, and the clustering of luminous red galaxies. We provide a Dockerized Jupyter notebook housing the fairly complex dependences for producing the plot of these data, with the hope that groups in the future can help add to it. Overall, we find qualitative agreement between the independent measurements considered here and the standard ΛCDM cosmological model fit to the Planck data.

scholarly journals Weak lensing cosmology with convolutional neural networks on noisy data

2019 ◽  
Vol 490 (2) ◽  
pp. 1843-1860 ◽  
Author(s):  
Dezső Ribli ◽  
Bálint Ármin Pataki ◽  
José Manuel Zorrilla Matilla ◽  
Daniel Hsu ◽  
Zoltán Haiman ◽  
...  
Keyword(s):  
Neural Networks ◽  
Correlation Function ◽  
Power Spectrum ◽  
Convolutional Neural Networks ◽  
Higher Order ◽  
Weak Lensing ◽  
Noise Levels ◽  
Point Correlation ◽  
Point Correlation Function ◽  
Non Gaussian

ABSTRACT Weak gravitational lensing is one of the most promising cosmological probes of the late universe. Several large ongoing (DES, KiDS, HSC) and planned (LSST, Euclid, WFIRST) astronomical surveys attempt to collect even deeper and larger scale data on weak lensing. Due to gravitational collapse, the distribution of dark matter is non-Gaussian on small scales. However, observations are typically evaluated through the two-point correlation function of galaxy shear, which does not capture non-Gaussian features of the lensing maps. Previous studies attempted to extract non-Gaussian information from weak lensing observations through several higher order statistics such as the three-point correlation function, peak counts, or Minkowski functionals. Deep convolutional neural networks (CNN) emerged in the field of computer vision with tremendous success, and they offer a new and very promising framework to extract information from 2D or 3D astronomical data sets, confirmed by recent studies on weak lensing. We show that a CNN is able to yield significantly stricter constraints of (σ8, Ωm) cosmological parameters than the power spectrum using convergence maps generated by full N-body simulations and ray-tracing, at angular scales and shape noise levels relevant for future observations. In a scenario mimicking LSST or Euclid, the CNN yields 2.4–2.8 times smaller credible contours than the power spectrum, and 3.5–4.2 times smaller at noise levels corresponding to a deep space survey such as WFIRST. We also show that at shape noise levels achievable in future space surveys the CNN yields 1.4–2.1 times smaller contours than peak counts, a higher order statistic capable of extracting non-Gaussian information from weak lensing maps.

Two-point Correlation Function and Power Spectrum at Very Large Scales

2005 ◽  
Vol 201 ◽  
pp. 449-450
Author(s):  
Z.-G. Deng ◽  
X.-Y. Xia
Keyword(s):  
Correlation Function ◽  
Power Spectrum ◽  
Correlation Functions ◽  
Large Scale ◽  
Wave Number ◽  
Scale Fluctuation ◽  
Point Correlation ◽  
Point Correlation Function ◽  
Redshift Survey ◽  
Large Scale Fluctuation

Subsamples of galaxies with different morphological types have been sorted out from Stromlo-APM redshift survey. Two-point correlation function for each subsample has been calculated. The two-point correlation functions for all subsamples show very large scale fluctuation. We show that the two-point correlation function with fluctuation could be fitted by a modified power spectrum with power excess at wave number comparable to the scale of the fluctuation.

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