scholarly journals Consistency of cosmic shear analyses in harmonic and real space

2021 ◽  
Author(s):  
C Doux ◽  
C Chang ◽  
B Jain ◽  
J Blazek ◽  
H Camacho ◽  
...  
Keyword(s):  
A Priori ◽  
Power Spectra ◽  
Correlation Coefficients ◽  
Stage Iv ◽  
Real Space ◽  
Multiple Sources ◽  
Dark Energy Survey ◽  
Statistical Fluctuations ◽  
Key Factor ◽  
Cosmic Shear

Abstract Recent cosmic shear studies have reported discrepancies of up to 1σ on the parameter ${S_{8}=\sigma _{8}\sqrt{{\Omega _{\rm m}}/0.3}}$ between the analysis of shear power spectra and two-point correlation functions, derived from the same shear catalogs. It is not a priori clear whether the measured discrepancies are consistent with statistical fluctuations. In this paper, we investigate this issue in the context of the forthcoming analyses from the third year data of the Dark Energy Survey (DES-Y3). We analyze DES-Y3 mock catalogs from Gaussian simulations with a fast and accurate importance sampling pipeline. We show that the methodology for determining matching scale cuts in harmonic and real space is the key factor that contributes to the scatter between constraints derived from the two statistics. We compare the published scales cuts of the KiDS, Subaru-HSC and DES surveys, and find that the correlation coefficients of posterior means range from over 80% for our proposed cuts, down to 10% for cuts used in the literature. We then study the interaction between scale cuts and systematic uncertainties arising from multiple sources: non-linear power spectrum, baryonic feedback, intrinsic alignments, uncertainties in the point-spread function, and redshift distributions. We find that, given DES-Y3 characteristics and proposed cuts, these uncertainties affect the two statistics similarly; the differential biases are below a third of the statistical uncertainty, with the largest biases arising from intrinsic alignment and baryonic feedback. While this work is aimed at DES-Y3, the tools developed can be applied to Stage-IV surveys where statistical errors will be much smaller.

scholarly journals The halo model as a versatile tool to predict intrinsic alignments

2020 ◽  
Author(s):  
Maria Cristina Fortuna ◽  
Henk Hoekstra ◽  
Benjamin Joachimi ◽  
Harry Johnston ◽  
Nora Elisa Chisari ◽  
...  
Keyword(s):  
Degrees Of Freedom ◽  
Power Spectra ◽  
Stage Iv ◽  
Stage Iii ◽  
Radial Dependence ◽  
Additional Parameter ◽  
Small Scales ◽  
Cosmic Shear ◽  
Galaxy Populations ◽  
The Impact

Abstract Intrinsic alignments (IAs) of galaxies are an important contaminant for cosmic shear studies, but the modelling is complicated by the dependence of the signal on the source galaxy sample. In this paper, we use the halo model formalism to capture this diversity and examine its implications for Stage-III and Stage-IV cosmic shear surveys. We account for the different IA signatures at large and small scales, as well for the different contributions from central/satellite and red/blue galaxies, and we use realistic mocks to account for the characteristics of the galaxy populations as a function of redshift. We inform our model using the most recent observational findings: we include a luminosity dependence at both large and small scales and a radial dependence of the signal within the halo. We predict the impact of the total IA signal on the lensing angular power spectra, including the current uncertainties from the IA best-fits to illustrate the range of possible impact on the lensing signal: the lack of constraints for fainter galaxies is the main source of uncertainty for our predictions of the IA signal. We investigate how well effective models with limited degrees of freedom can account for the complexity of the IA signal. Although these lead to negligible biases for Stage-III surveys, we find that, for Stage-IV surveys, it is essential to at least include an additional parameter to capture the redshift dependence.

scholarly journals Sufficiency of a Gaussian power spectrum likelihood for accurate cosmology from upcoming weak lensing surveys

2021 ◽  
Author(s):  
Robin E Upham ◽  
Michael L Brown ◽  
Lee Whittaker
Keyword(s):  
Power Spectrum ◽  
Random Noise ◽  
Power Spectra ◽  
Stage Iv ◽  
Wishart Distribution ◽  
Weak Lensing ◽  
Dependence Structure ◽  
Gaussian Fields ◽  
Non Gaussian ◽  
Parameter Constraints

Abstract We investigate whether a Gaussian likelihood is sufficient to obtain accurate parameter constraints from a Euclid-like combined tomographic power spectrum analysis of weak lensing, galaxy clustering and their cross-correlation. Testing its performance on the full sky against the Wishart distribution, which is the exact likelihood under the assumption of Gaussian fields, we find that the Gaussian likelihood returns accurate parameter constraints. This accuracy is robust to the choices made in the likelihood analysis, including the choice of fiducial cosmology, the range of scales included, and the random noise level. We extend our results to the cut sky by evaluating the additional non-Gaussianity of the joint cut-sky likelihood in both its marginal distributions and dependence structure. We find that the cut-sky likelihood is more non-Gaussian than the full-sky likelihood, but at a level insufficient to introduce significant inaccuracy into parameter constraints obtained using the Gaussian likelihood. Our results should not be affected by the assumption of Gaussian fields, as this approximation only becomes inaccurate on small scales, which in turn corresponds to the limit in which any non-Gaussianity of the likelihood becomes negligible. We nevertheless compare against N-body weak lensing simulations and find no evidence of significant additional non-Gaussianity in the likelihood. Our results indicate that a Gaussian likelihood will be sufficient for robust parameter constraints with power spectra from Stage IV weak lensing surveys.

scholarly journals KiDS+VIKING-450 and DES-Y1 combined: Cosmology with cosmic shear

2020 ◽  
Vol 638 ◽  
pp. L1 ◽  
Author(s):  
S. Joudaki ◽  
H. Hildebrandt ◽  
D. Traykova ◽  
N. E. Chisari ◽  
C. Heymans ◽  
...  
Keyword(s):  
Dark Energy ◽  
Cosmic Microwave Background ◽  
Gravitational Lensing ◽  
Error Model ◽  
Calibration Error ◽  
Microwave Background ◽  
Weak Gravitational Lensing ◽  
Dark Energy Survey ◽  
Cosmic Shear ◽  
Energy Survey

We present a combined tomographic weak gravitational lensing analysis of the Kilo Degree Survey (KV450) and the Dark Energy Survey (DES-Y1). We homogenize the analysis of these two public cosmic shear datasets by adopting consistent priors and modeling of nonlinear scales, and determine new redshift distributions for DES-Y1 based on deep public spectroscopic surveys. Adopting these revised redshifts results in a 0.8σ reduction in the DES-inferred value for S​8, which decreases to a 0.5σ reduction when including a systematic redshift calibration error model from mock DES data based on the MICE2 simulation. The combined KV450+DES-Y1 constraint on S8 = 0.762−0.024+0.025 is in tension with the Planck 2018 constraint from the cosmic microwave background at the level of 2.5σ. This result highlights the importance of developing methods to provide accurate redshift calibration for current and future weak-lensing surveys.

scholarly journals Management control systems, organization and impact on performances: Evidences from Italy

2017 ◽  
Vol 14 (2) ◽  
pp. 250-257
Author(s):  
Elisa Truant
Keyword(s):  
Intellectual Capital ◽  
Management Control ◽  
Management Systems ◽  
Incentive Systems ◽  
Multiple Sources ◽  
Management Tools ◽  
Accounting Systems ◽  
Corporate Managers ◽  
Key Factor ◽  
Depth Study

The value creation is the primary goal of each organization and intellectual capital is certainly a key factor for long-term success. The intellectual capital variables have to be managed and measured within advanced management systems, in order to facilitate the communication and translation of strategy’s tangible and intangible elements into operational terms. This study focuses on a sample of medium-sized Italian firms and is based on multiple sources of evidence: the in-depth study of internal documents and interviews with corporate managers holding key positions within the organization. The research aims at investigating if managers identified, measured and monitored intellectual capital variables within advanced management accounting systems, over a period of 5 years. Because the strategy and the organizational structure are highly interdependent, this study also focuses on evaluation and incentive systems implemented within selected companies. Then, it was decided to analyze whether the use of managerial and organizational tools influence firms’ performances. This research contributes to extend existing literature on intellectual capital and management systems: the results revealed that companies able to manage and monitor intellectual capital within advanced management tools, as well as implement evaluation and incentive systems, achieved higher and more stable performances. The main limit of this study is strictly related to the choice of these variables: in fact, company’s performances are influenced by a significant number of factors, endogenous and exogenous to the organization. Future researches can involve a greater number of companies and organizational variables, in order to validate or confute the actual findings.

Fundamental statistical techniques for the analysis of earth tides

1971 ◽  
Vol 61 (1) ◽  
pp. 203-215
Author(s):  
Cheh Pan
Keyword(s):  
Computer Technology ◽  
Earth Tide ◽  
Power Spectra ◽  
Correlation Coefficients ◽  
Earth Tides ◽  
Statistical Techniques ◽  
The Earth ◽  
Tidal Data ◽  
Instrumental Drift ◽  
Phase Differences

abstract Recent advances in instrumentation, digital computer technology and mathematical theory promote the error analysis of Earth-tide data. Various statistical techniques developed and used in other fields are applicable in the study of Earth tides, and the accuracy of the Earth's rigidity constants determined from the tides will be greatly improved with the help of these techniques. The fundamentals of the statistical techniques of autocorrelation, crosscorrelation, convolution, statistical means, bandpass filtering, correlation coefficients, power spectra, coherency and equalization are described, and their principal applications in the Earth-tide analysis summarized. Examples of effective application of these techniques in the elimination of the errors in the tidal data such as those introduced from instrumental drift, phase differences between the observed and predicted tides, etc. are discussed. This work is an attempt to introduce statistical analysis into the Earth-tide study.

scholarly journals Inference from the small scales of cosmic shear with current and future Dark Energy Survey data

2016 ◽  
Vol 465 (3) ◽  
pp. 2567-2583 ◽  
Author(s):  
N. MacCrann ◽  
J. Aleksić ◽  
A. Amara ◽  
S. L. Bridle ◽  
C. Bruderer ◽  
...  
Keyword(s):  
Dark Energy ◽  
Survey Data ◽  
Dark Energy Survey ◽  
Small Scales ◽  
Cosmic Shear ◽  
Energy Survey

scholarly journals Why female birds of prey are larger than males

2020 ◽  
Vol 129 (3) ◽  
pp. 532-542
Author(s):  
Jonny Schoenjahn ◽  
Chris R Pavey ◽  
Gimme H Walter
Keyword(s):  
Sexual Size Dimorphism ◽  
A Priori ◽  
Nest Defence ◽  
Birds Of Prey ◽  
Causal Process ◽  
Size Dimorphism ◽  
Substantial Body ◽  
Key Factor ◽  
Reversed Sexual Size Dimorphism ◽  
Passionate Debate

Abstract The causes of the reversed sexual size dimorphism (RSD; females larger than males) in birds of prey are subject to a centuries-old, passionate debate. A crucial difficulty is to distinguish whether the postulated benefits derive from the proposed causal process(es) or are incidental. After reviewing the existing literature, we present a methodology that overcomes this difficulty and renders unnecessary any speculative a priori distinctions between evolved function and incidental effects. We can thus justify the following novel version of the well-known nest defence hypothesis as the most likely to explain the phenomenon in all birds of prey that show RSD: if the female predominates in actively defending the eggs and young against predators, then she is the heavier sex, and her relatively greater body mass is adaptive. That is, heavier females are favoured (independently of males) by natural selection. The attractiveness of this hypothesis is that it has the potential to explain the phenomenon in all raptors exhibiting RSD, can deal with the exceptional cases in this group, explains the direction of the dimorphism, focuses on a key factor in the reproductive success of most raptors, is parsimonious, i.e. does not require supporting hypotheses, and is supported by a substantial body of evidence.

scholarly journals Standardising the measurement of physical activity in people receiving haemodialysis: considerations for research and practice

2019 ◽  
Vol 20 (1) ◽  
Author(s):  
Hannah M. L. Young ◽  
Mark W. Orme ◽  
Yan Song ◽  
Maurice Dungey ◽  
James O. Burton ◽  
...  
Keyword(s):  
Physical Activity ◽  
Sample Size ◽  
Repeated Measures ◽  
A Priori ◽  
Intraclass Correlation ◽  
Correlation Coefficients ◽  
Future Research ◽  
Wear Time ◽  
Minimum Number ◽  
The Uk

Abstract Background Physical activity (PA) is exceptionally low amongst the haemodialysis (HD) population, and physical inactivity is a powerful predictor of mortality, making it a prime focus for intervention. Objective measurement of PA using accelerometers is increasing, but standard reporting guidelines essential to effectively evaluate, compare and synthesise the effects of PA interventions are lacking. This study aims to (i) determine the measurement and processing guidance required to ensure representative PA data amongst a diverse HD population, and; (ii) to assess adherence to PA monitor wear amongst HD patients. Methods Clinically stable HD patients from the UK and China wore a SenseWear Armband accelerometer for 7 days. Step count between days (HD, Weekday, Weekend) were compared using repeated measures ANCOVA. Intraclass correlation coefficients (ICCs) determined reliability (≥0.80 acceptable). Spearman-Brown prophecy formula, in conjunction with a priori ≥  80% sample size retention, identified the minimum number of days required for representative PA data. Results Seventy-seven patients (64% men, mean ± SD age 56 ± 14 years, median (interquartile range) time on HD 40 (19–72) months, 40% Chinese, 60% British) participated. Participants took fewer steps on HD days compared with non-HD weekdays and weekend days (3402 [95% CI 2665–4140], 4914 [95% CI 3940–5887], 4633 [95% CI 3558–5707] steps/day, respectively, p < 0.001). PA on HD days were less variable than non-HD days, (ICC 0.723–0.839 versus 0.559–0.611) with ≥ 1 HD day and ≥  3 non-HD days required to provide representative data. Using these criteria, the most stringent wear-time retaining ≥ 80% of the sample was ≥7 h. Conclusions At group level, a wear-time of ≥7 h on ≥1HD day and ≥ 3 non-HD days is required to provide reliable PA data whilst retaining an acceptable sample size. PA is low across both HD and non- HD days and future research should focus on interventions designed to increase physical activity in both the intra and interdialytic period.

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