scholarly journals Effects of long-wavelength fluctuations in large galaxy surveys

2019 ◽  
Vol 489 (2) ◽  
pp. 1684-1696 ◽  
Author(s):  
Anatoly Klypin ◽  
Francisco Prada
Keyword(s):  
Dark Matter ◽  
Finite Volume ◽  
Average Power ◽  
Power Spectra ◽  
Covariance Matrices ◽  
Galaxy Surveys ◽  
Long Wavelength ◽  
Ideal Situation ◽  
Mass Functions ◽  
The Ideal

ABSTRACT In order to capture as much information as possible large galaxies surveys have been increasing their volume and redshift depth. To face this challenge theory has responded by making cosmological simulations of huge computational volumes with equally increasing numbers of dark matter particles and supercomputing resources. Thus, it is taken for granted that the ideal situation is when a single computational box encompasses the whole volume of the observational survey, e.g. $\sim 50\, h^{-3}\,{\rm Gpc}^3$ for the DESI and Euclid surveys. Here we study the effects of missing long waves in a finite volume using several relevant statistics: the abundance of dark matter haloes, the probability distribution function (PDF), the correlation function and power spectrum, and covariance matrices. Finite volume effects can substantially modify the results if the computational volumes are less than $\sim (500\mbox{$\, h^{-1}$Mpc})^3$. However, the effects become extremely small and practically can be ignored when the box size exceeds ∼1 Gpc3. We find that the average power spectra of dark matter fluctuations show remarkable lack of dependence on the computational box size with less than 0.1 per cent differences between $1$ and $4\mbox{$\, h^{-1}\,$Gpc}$ boxes. No measurable differences are expected for the halo mass functions for these volumes. The covariance matrices are scaled trivially with volume, and small corrections due to supersample modes can be added. We conclude that there is no need to make those extremely large simulations when a box size of $1-1.5\mbox{$\, h^{-1}$Gpc}$ is sufficient to fulfil most of the survey science requirements.

scholarly journals The anisotropy of the power spectrum in periodic cosmological simulations

2021 ◽  
Vol 503 (4) ◽  
pp. 5638-5645
Author(s):  
Gábor Rácz ◽  
István Szapudi ◽  
István Csabai ◽  
László Dobos
Keyword(s):  
Dark Matter ◽  
Power Spectrum ◽  
Large Scale ◽  
Cold Dark Matter ◽  
Initial Conditions ◽  
Power Spectra ◽  
Cosmological Simulations ◽  
Spherical Collapse ◽  
Lower Amplitude ◽  
Hydrodynamical Simulations

ABSTRACT The classical gravitational force on a torus is anisotropic and always lower than Newton’s 1/r2 law. We demonstrate the effects of periodicity in dark matter only N-body simulations of spherical collapse and standard Lambda cold dark matter (ΛCDM) initial conditions. Periodic boundary conditions cause an overall negative and anisotropic bias in cosmological simulations of cosmic structure formation. The lower amplitude of power spectra of small periodic simulations is a consequence of the missing large-scale modes and the equally important smaller periodic forces. The effect is most significant when the largest mildly non-linear scales are comparable to the linear size of the simulation box, as often is the case for high-resolution hydrodynamical simulations. Spherical collapse morphs into a shape similar to an octahedron. The anisotropic growth distorts the large-scale ΛCDM dark matter structures. We introduce the direction-dependent power spectrum invariant under the octahedral group of the simulation volume and show that the results break spherical symmetry.

scholarly journals 3 per cent-accurate predictions for the clustering of dark matter, haloes, and subhaloes, over a wide range of cosmologies and scales

2020 ◽  
Vol 499 (4) ◽  
pp. 4905-4917
Author(s):  
S Contreras ◽  
R E Angulo ◽  
M Zennaro ◽  
G Aricò ◽  
M Pellejero-Ibañez
Keyword(s):  
Dark Matter ◽  
Spatial Distribution ◽  
Cosmological Parameters ◽  
Galaxy Surveys ◽  
Circular Velocity ◽  
Initial Application ◽  
Wide Range ◽  
Massive Neutrinos ◽  
Dynamical Dark Energy ◽  
Better Than

ABSTRACT Predicting the spatial distribution of objects as a function of cosmology is an essential ingredient for the exploitation of future galaxy surveys. In this paper, we show that a specially designed suite of gravity-only simulations together with cosmology-rescaling algorithms can provide the clustering of dark matter, haloes, and subhaloes with high precision. Specifically, with only three N-body simulations, we obtain the power spectrum of dark matter at z = 0 and 1 to better than 3 per cent precision for essentially all currently viable values of eight cosmological parameters, including massive neutrinos and dynamical dark energy, and over the whole range of scales explored, 0.03 < $k/{h}^{-1}\, {\rm Mpc}^{-1}$ < 5. This precision holds at the same level for mass-selected haloes and for subhaloes selected according to their peak maximum circular velocity. As an initial application of these predictions, we successfully constrain Ωm, σ8, and the scatter in subhalo-abundance-matching employing the projected correlation function of mock SDSS galaxies.

scholarly journals Statistical analysis of second order effects variation with the stories height of reinforced concrete buildings

2017 ◽  
Vol 10 (2) ◽  
pp. 333-357
Author(s):  
D.M. OLIVEIRA ◽  
N.A. SILVA ◽  
C.C. RIBEIRO ◽  
S.E.C. RIBEIRO
Keyword(s):  
Reinforced Concrete ◽  
Statistical Analysis ◽  
Second Order ◽  
Order Effects ◽  
Reinforced Concrete Buildings ◽  
First Order ◽  
Concrete Buildings ◽  
Ideal Situation ◽  
Second Order Effects ◽  
The Ideal

Abstract In this paper the simplified method to evaluate final efforts using γ z coefficient is studied considering the variation of the second order effects with the height of the buildings. With this purpose, several reinforced concrete buildings of medium height are analyzed in first and second order using ANSYS software. Initially, it was checked that the (z coefficient should be used as magnifier of first order moments to evaluate final second order moments. Therefore, the study is developed considering the relation (final second order moments/ first order moments), calculated for each story of the structures. This moments relation is called magnifier of first order moments, "γ", and, in the ideal situation, it must coincide with the γ z value. However, it is observed that the reason γ /γ z varies with the height of the buildings. Furthermore, using an statistical analysis, it was checked that γ /γ z relation is generally lower than 1.05 and varies significantly in accordance with the considered building and with the presence or not of symmetry in the structure.

scholarly journals KONSEP DIRI ANAK PEKERJA SEKS KOMERSIAL YANG TINGGAL DITENGAH MASYARAKAT

2017 ◽  
Vol 1 (1) ◽  
pp. 78
Author(s):  
Fatchun Nikmah
Keyword(s):  
Physical Condition ◽  
Sex Workers ◽  
Self Concept ◽  
Snowball Sampling ◽  
Ideal Self ◽  
Study Approach ◽  
Ideal Situation ◽  
The Subject ◽  
The Ideal

Abstract  Stigma in today's society considers more sex workers as the dregs of society who only regarded as an immoral person who violates the norms of religion and society, so they are not appreciated. A prostitute is almost the majority have families, both parents, brother, husband or child. Communities usually negative view sex workers family and those views may influence the psychological development of child prostitutes. This study aims to determine the child's self-concept of prostitutes who live in the community.This study uses a qualitative case study approach, which is a special phenomenon that is present in a limited context, although the boundaries between phenomenon and context are not entirely clear. Determination techniques are the subject of the researchers used snowball sampling or chain sampling. The research was conducted in two villages that are within the scope of the district in one district on the island of Java. The subject of this study were children and adolescents aged prostitute who is still undergoing formal schooling.This study found that the first subject has a good self concept. There is not much of a gap between the basic self-concept and ideal self-concept on the subject. The first subject has a perceptual self-concept is not good because the subject is not satisfied with the current physical condition and there are gaps in the basic perceptual components and ideal self-concept. As for the conceptual and attitudinal self concept self concept can be considered a good subject because there is no gap between the conceptual and attitudinal components of the basic categories and ideal self-concept. While the second subject has a poor self-concept, as there are many gaps between the basic self-concept and ideal self concept on the subject. The subject has a perceptual selfconcept is not good, because the subject was not satisfied with his physical condition and his subjects make the situation as a benchmark of the ideal situation for him. In addition, the subject has attitudinal poor self concept.  Keywords: Self-concept, children, sex workers, society, qualitative

scholarly journals Anti-symmetric clustering signals in the observed power spectrum

2021 ◽  
Vol 2021 (12) ◽  
pp. 003
Author(s):  
José Fonseca ◽  
Chris Clarkson
Keyword(s):  
Dark Matter ◽  
Power Spectrum ◽  
Euler Equation ◽  
Large Scale ◽  
Signal To Noise Ratio ◽  
Power Spectra ◽  
Large Scale Structure ◽  
Scale Structure ◽  
Signal To Noise ◽  
Peculiar Velocities

Abstract In this paper, we study how to directly measure the effect of peculiar velocities in the observed angular power spectra. We do this by constructing a new anti-symmetric estimator of Large Scale Structure using different dark matter tracers. We show that the Doppler term is the major component of our estimator and we show that we can measure it with a signal-to-noise ratio up to ∼ 50 using a futuristic SKAO HI galaxy survey. We demonstrate the utility of this estimator by using it to provide constraints on the Euler equation.

scholarly journals Effective dark matter power spectra inf(R)gravity

2015 ◽  
Vol 92 (10) ◽  
Author(s):  
Jian-hua He ◽  
Baojiu Li ◽  
Adam J. Hawken
Keyword(s):  
Dark Matter ◽  
Power Spectra

The role of aerocosmic research in metallogenic prediction (on the example of antimony-mercury ore formation deposits in Azerbaijan)

2020 ◽  
Vol 02 (03) ◽  
pp. 55-60
Author(s):  
Zaki Abdulla Valiyev ◽  
Keyword(s):  
Total Mercury ◽  
Ore Formation ◽  
Aerospace Research ◽  
The Earth ◽  
Ideal Situation ◽  
Metallogenic Prediction ◽  
Key Words Mercury ◽  
Deep Fractures ◽  
The Ideal

Mercury degassing is a global process. In geological development, it begins with the formation of deep fractures that can penetrate the great depths of the mantle. As the linearity lengthens, the temporal degassing and intensity of mercury weaken this connection with the depths of its individual parts and the Earth, or the period of strengthening of this connection will vary depending on the development of the characteristics observed. The concentration of mercury and antimony-mercury ores along the outer frame of circular and oval and other structures can most likely be explained by the Earth's total mercury degassing. In our opinion, the ideal situation is the junction of circular, oval, and other structures with linear nodes, where industrially important deposits of minerals can be formed. Key words: mercury, aerospace research, metallogenic prediction, minerals

In Praise of Useful Articles

PEDIATRICS ◽  
1981 ◽  
Vol 68 (5) ◽  
pp. 753-753
Author(s):  
William F. Schnitzker
Keyword(s):  
Lumbar Puncture ◽  
Clinical Features ◽  
Clinical Suspicion ◽  
Routine Investigation ◽  
Ideal Situation ◽  
The Ideal

Many thanks to Apollo, Aesculapius, Hygeia, Panacea, and all the gods and goddesses of health for the May 1981 issue of Pediatrics. In "Fever and Convulsions..." Jaffe et al concluded "that the only routine investigation indicatd, even in the absence of clinical suspicion, is a lumbar puncture. In ideal situations even this procedure may be omitted. Other investigations should be performed only if the clinical features of the case warrant them." I would amend the "ideal situation" to: if and when a clinician with the usual qualification to practice is available, the lumbar puncture should be omitted.

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