Material content of the Universe: meeting summary

1986 ◽  
Vol 320 (1556) ◽  
pp. 609-611
Keyword(s):  
Cosmological Model ◽  
Mass Distribution ◽  
Large Scale ◽  
Mean Value ◽  
De Sitter ◽  
Cosmic Evolution ◽  
Broad Variety ◽  
The Mean ◽  
The Universe ◽  
General Synthesis

We have considered what might be said about the large-scale distribution of mass in the Universe and in particular whether the mean value might agree with the Einstein-de Sitter cosmological model; what might be said about the composition of the mass as a function of position, and in particular whether we can convince ourselves that exotic matter plays a significant role in some regions; and what might be said about the cosmic evolution of the mass distribution and composition. The present state of our debate is notable for the broad variety of interesting-looking clues and the lack of general agreement on how they might fit together in some general synthesis.

Cosmological spacetimes

2018 ◽  
Author(s):  
Nathalie Deruelle ◽  
Jean-Philippe Uzan
Keyword(s):  
Cosmological Model ◽  
Large Scale ◽  
Cosmic Time ◽  
De Sitter ◽  
Matter Distribution ◽  
Observable Universe ◽  
Cosmological Principle ◽  
Riemannian Spacetime ◽  
The Universe ◽  
Copernican Principle

This chapter provides a few examples of representations of the universe on a large scale—a first step in constructing a cosmological model. It first discusses the Copernican principle, which is an approximation/hypothesis about the matter distribution in the observable universe. The chapter then turns to the cosmological principle—a hypothesis about the geometry of the Riemannian spacetime representing the universe, which is assumed to be foliated by 3-spaces labeled by a cosmic time t which are homogeneous and isotropic, that is, ‘maximally symmetric’. After a discussion on maximally symmetric space, this chapter considers spacetimes with homogenous and isotropic sections. Finally, this chapter discusses Milne and de Sitter spacetimes.

scholarly journals LARGE SCALE ANISOTROPY DUE TO PRE-INFLATIONARY PHASE OF COSMIC EVOLUTION

2012 ◽  
Vol 27 (04) ◽  
pp. 1250014 ◽  
Author(s):  
PAVAN K. ALURI ◽  
PANKAJ JAIN
Keyword(s):  
Large Scale ◽  
Cosmological Evolution ◽  
Cosmic Evolution ◽  
Cosmological Observations ◽  
Inflationary Phase ◽  
The Universe ◽  
Dipole Modulation

We show that perturbations generated during the anisotropic pre-inflationary stage of cosmic evolution may affect cosmological observations today for a certain range of parameters. Due to the anisotropic nature of the universe during such early times, it might explain some of the observed signals of large scale anisotropy. In particular, we argue that the alignment of CMB quadrupole and octopole may be explained by the Sachs–Wolfe effect due to the large scale anisotropic modes from very early times of cosmological evolution. We also comment on how the observed dipole modulation of CMB power may be explained within this framework.

Synchronous Issue of IR-Based Large Scale Volume Localization System

2014 ◽  
Vol 496-500 ◽  
pp. 1643-1647
Author(s):  
Ying Feng Wu ◽  
Gang Yan Li
Keyword(s):  
Standard Deviation ◽  
Mobile Robot ◽  
Large Volume ◽  
Large Scale ◽  
Image Acquisition ◽  
Mean Value ◽  
Network Synchronization ◽  
Localization System ◽  
Localization Performance ◽  
The Mean

IR-based large scale volume localization system (LSVLS) can localize the mobile robot working in large volume, which is constituted referring to the MSCMS-II. Hundreds cameras in LSVLS must be connected to the control station (PC) through network. Synchronization of cameras which are mounted on different control stations is significant, because the image acquisition of the target must be synchronous to ensure that the target is localized precisely. Software synchronization method is adopted to ensure the synchronization of camera. The mean value of standard deviation of eight cameras mounted on two workstations is 12.53ms, the localization performance of LSVLS is enhanced.

scholarly journals Large-Scale Structure of the Universe in Unstable Dark Matter Models

1988 ◽  
Vol 130 ◽  
pp. 293-300
Author(s):  
A.G. Doroshkevich ◽  
A.A. Klypin ◽  
M.U. Khlopov
Keyword(s):  
Dark Matter ◽  
Galaxy Formation ◽  
Large Scale ◽  
Numerical Models ◽  
Large Scale Structure ◽  
Scale Structure ◽  
Microwave Background ◽  
Physical Background ◽  
The Mean ◽  
The Universe

Processes of the formation and the evolution of the large-scale structure are discussed in the framework of unstable dark matter models. Six numerical models are presented. The projected distribution of simulated galaxies on the sky, wedge diagrams, correlation functions and the mean linear scale of voids are presented. Physical background of the hypothesis of unstable particles and possible observational tests are discussed. The level of the microwave background fluctuations is estimated analytically. Special attention is given to late stage of supercluster evolution and galaxy formation.

scholarly journals The Large Number Hypothesis and Einstein's Theory of Gravitation

1985 ◽  
Vol 38 (4) ◽  
pp. 547 ◽  
Author(s):  
Yun-Kau Lau
Keyword(s):  
Cosmological Model ◽  
Cosmological Constant ◽  
Matter Density ◽  
Time Dependent ◽  
Field Equations ◽  
Large Number Hypothesis ◽  
Theory Of Gravitation ◽  
The Mean ◽  
Limiting Case ◽  
The Universe

In an attempt to reconcile the large number hypothesis (LNH) with Einstein's theory of gravitation, a tentative generalization of Einstein's field equations with time-dependent cosmological and gravitational constants is proposed. A cosmological model consistent with the LNH is deduced. The coupling formula of the cosmological constant with matter is found, and as a consequence, the time-dependent formulae of the cosmological constant and the mean matter density of the Universe at the present epoch are then found. Einstein's theory of gravitation, whether with a zero or nonzero cosmological constant, becomes a limiting case of the new generalized field equations after the early epoch.

scholarly journals Biased Galaxy Formation and Dark Matter

1988 ◽  
Vol 130 ◽  
pp. 437-446
Author(s):  
Martin J. Rees
Keyword(s):  
Dark Matter ◽  
Cosmological Model ◽  
Mass Distribution ◽  
Galaxy Formation ◽  
Formation Process ◽  
Large Scale

The clustering properties of galaxies are incompatible with a cosmological model with Ω = 1 unless the formation process for bright galaxies is ‘biased’ in the sense that their resultant distribution exaggerates the amplitude of large-scale inhomogeneities in the overall mass distribution. The mechanisms for such biasing are intimately connected with the nature of the dark matter. Various possibilities are summarised here.

Analysis of Synergies among the Ecological Factors of Farmland in a Township

2014 ◽  
Vol 556-562 ◽  
pp. 916-920
Author(s):  
Yu Huan Li ◽  
Deng Qiu Li ◽  
Jie Wu
Keyword(s):  
Large Scale ◽  
Ecological Factors ◽  
Mean Value ◽  
Small Scale ◽  
Medium Scale ◽  
Factorial Kriging ◽  
Spherical Models ◽  
Scale Range ◽  
The Mean ◽  
High Coordination

The spatial variability of single ecological factors of the farmland and the synergies among the ecological factors were studied by using geostatistical analysis and factorial kriging analysis (FKA).The results show that all of the spherical models of the co-variogram can be grouped into four parts: the nugget part, the small-scale part, the medium-scale part, and the large-scale part. The mean value of the small-scale range (1.12-1.85 km) is approximately 1.50 km, that of the medium-scale range (3.40-4.10 km) is approximately 3.8 km, and that of the large-scale range (9.35-10.10 km) is approximately 9.8 km. The correlations between each factor on the four scales vary, and the correlation between each factor on the medium scale is the strongest. In this paper, the ecological factors of the farmland on the medium scale have relatively consistent variability and sources, indicating that all of the factors on that scale have a high coordination.

scholarly journals The Asymmetric Cosmic Time – The Key to a New Cosmological Model

2020 ◽  
Vol 2 (1) ◽  
pp. 97-111
Author(s):  
Horst Fritsch ◽  
Eberhard Schluecker
Keyword(s):  
Cosmological Model ◽  
Initial Conditions ◽  
Logical Consequence ◽  
Cosmic Time ◽  
Big Bang ◽  
Relativity Theory ◽  
Accelerated Expansion ◽  
Theory Of Relativity ◽  
De Sitter ◽  
The Universe

The asymmetric cosmic time is a logical consequence of the General Theory of Relativity (GR), if one demands that it should apply to the entire cosmos. From the simplest cosmological model that is consistent with the ART (Einstein-de Sitter model) thus follows the < Cosmic Time Hypothesis > (CTH), which offers solutions for many unsolved problems of cosmology that the current standard model of cosmology (ɅCDM model) cannot explain. According to the CTH, space, time and matter form a unit and develop evolutionarily according to identical, time-dependent laws. According to the CTH time has neither beginning nor end. The "big bang" disappears into the infinite past, which is why the universe manages without inflation. The accelerated expansion of the universe is also unlikely to occur if the SN-Ia measurement results are interpreted using the CTH. The cosmological constant Ʌ can then be omitted (Ʌ=0) and consequently no "dark energy" is needed. In addition, the CTH also provides interesting results on the topics: Initial conditions for hypotheses, stability of the expanding, flat universe (Ω=1), cosmic energy balance (is there negative energy ?), theory of earth expansion, unification of natural forces, Mach's principle. Should the CTH receive broad experimental confirmation, the GR could be extended to the "Universal Relativity Theory" (UR).

scholarly journals Assessment of sagittal spinopelvic alignment in asymptomatic Chinese juveniles and adolescents: a large cohort study and comparative meta-analysis

2021 ◽  
Vol 16 (1) ◽  
Author(s):  
Canglong Hou ◽  
Kai Chen ◽  
Yu Chen ◽  
Tianjunke Zhou ◽  
Mingyuan Yang ◽  
...  
Keyword(s):  
Cohort Study ◽  
Large Scale ◽  
Meta Analysis ◽  
Mean Value ◽  
Large Cohort ◽  
Mean Values ◽  
Spinopelvic Alignment ◽  
Large Cohort Study ◽  
Sagittal Parameters ◽  
The Mean

Abstract Study design Retrospective study and comparative meta-analysis. Objective To document the sagittal spinopelvic alignment in a large cohort study in asymptomatic Chinese juveniles and adolescents, and to explore whether these parameters were different from various regions using meta-analysis. Methods Medical records of 656 asymptomatic Chinese juveniles and adolescents were reviewed, whose mean age was 13.14 ± 3.41 years old, including 254 male and 402 female volunteers. Demographic and lateral radiological parameters were evaluated. Furthermore, a systematic online search was performed to identify eligible studies. Weight mean difference (WMD) with 95% confidence interval (CI) were used to evaluate whether these sagittal parameters were different from various regions. Results The mean value of sagittal spinopelvic alignment in this study was calculated and analyzed respectively. Significant differences of PI (34.20 ± 4.00 vs. 43.18 ± 7.12, P < 0.001) and PT (3.99 ± 6.04 vs. 8.42 ± 7.08, P < 0.001) were found between juveniles and adolescents. A total of 17 studies were recruited for meta-analysis. For juvenile populations, TK, PI and SS of Caucasians were significantly larger than those of our study (all P < 0.001). As for adolescent populations, PI (P = 0.017), TK (P = 0.017) and SS (P < 0.001) of Caucasians was found to be greater when compared with that of our study. All in all, TK, PI and SS in Chinese pre-adult populations were significantly smaller than those populations in Caucasian regions (all P < 0.001). Conclusion Our study was the first large-scale study that reported the mean values of sagittal parameters in asymptomatic Chinese juveniles and adolescents. There were significant differences in TK, PI and SS between our study and other previous reported populations, which reminded us for using specific mean values in different populations when restoring a relatively normal sagittal spinopelvic balance in spinal deformity.

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