scholarly journals Viscosity in cosmic fluids

2020 ◽  
Vol 80 (8) ◽  
Author(s):  
Pravin Kumar Natwariya ◽  
Jitesh R. Bhatt ◽  
Arun Kumar Pandey
Keyword(s):  
Dark Matter ◽  
Effective Viscosity ◽  
Large Scale ◽  
Significant Contribution ◽  
Viscosity Coefficient ◽  
Effective Theory ◽  
Viscous Effect ◽  
Dissipative Effects ◽  
Large Scale Structure Formation

Abstract The effective theory of large-scale structure formation based on $$\Lambda $$ΛCDM paradigm predicts finite dissipative effects in the resulting fluid equations. In this work, we study how viscous effect that could arise if one includes self-interaction among the dark-matter particles combines with the effective theory. It is shown that these two possible sources of dissipation can operate together in a cosmic fluid and the interplay between them can play an important role in determining dynamics of the cosmic fluid. In particular, we demonstrate that the viscosity coefficient due to self-interaction is added inversely with the viscosity calculated using effective theory of $$\Lambda $$ΛCDM model. Thus the larger viscosity has less significant contribution in the effective viscosity. Using the known bounds on $$\sigma /m$$σ/m for self-interacting darkmatter, where $$\sigma $$σ and m are the cross-section and mass of the dark-matter particles respectively, we discuss role of the effective viscosity in various cosmological scenarios.

Observational and astrophysical cosmology: 1980–2018

2019 ◽  
pp. 375-423
Author(s):  
Malcolm S. Longair
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Cosmological Constant ◽  
Large Scale ◽  
Cosmological Parameters ◽  
Semiconductor Detectors ◽  
Empirical Knowledge ◽  
Global Geometry ◽  
The Universe ◽  
Large Scale Structure Formation

Since 1980, our empirical knowledge of the universe has advanced tremendously and precision cosmology has become a reality. These developments have been largely technology-driven, the result of increased computer power, new generations of telescopes for all wavebands, new types of semiconductor detectors, such as CCDs, and major investments by many nations in superb observing facilities. The discipline also benefitted from the influx of experimental and theoretical physicists into the cosmological arena. The accuracy and reliability of the values of the cosmological parameters has improved dramatically, many of them now being known to about 1%. The ΛCDM model provides a remarkable fit to all the observational data, demonstrating that the cosmological constant is non-zero and that the global geometry of the universe is flat. The underlying physics of galaxy and large-scale structure formation has advanced dramatically and demonstrated the key roles played by dark matter and dark energy.

scholarly journals The fate of magnetic fields in colliding galaxies

2010 ◽  
Vol 6 (S274) ◽  
pp. 376-380
Author(s):  
Hanna Kotarba ◽  
Harald Lesch ◽  
Klaus Dolag ◽  
Thorsten Naab
Keyword(s):  
Dark Matter ◽  
High Resolution ◽  
Magnetic Fields ◽  
Structure Formation ◽  
Large Scale ◽  
Cold Dark Matter ◽  
Gravitational Interaction ◽  
Interacting Galaxies ◽  
Galactic Dynamics

AbstractThe evolution and amplification of large-scale magnetic fields in galaxies is investigated by means of high resolution simulations of interacting galaxies. The goal of our project is to consider in detail the role of gravitational interaction of galaxies for the fate of magnetic fields. Since the tidal interaction up to galaxy merging is a basic ingredient of cold-dark matter (CDM) structure formation models we think that our simulations will give important clues for the interplay of galactic dynamics and magnetic fields.

scholarly journals Beyond single-stream with the Schrödinger method

2014 ◽  
Vol 11 (S308) ◽  
pp. 115-118
Author(s):  
Cora Uhlemann ◽  
Michael Kopp
Keyword(s):  
Dark Matter ◽  
Phase Space ◽  
Poisson Equation ◽  
Large Scale ◽  
Fluid Model ◽  
Numerical Technique ◽  
Analytical Tool ◽  
The Common ◽  
Large Scale Structure Formation ◽  
Space Description

AbstractWe investigate large scale structure formation of collisionless dark matter in the phase space description based on the Vlasov-Poisson equation. We present the Schrödinger method, originally proposed by \cite{WK93} as numerical technique based on the Schrödinger Poisson equation, as an analytical tool which is superior to the common standard pressureless fluid model. Whereas the dust model fails and develops singularities at shell crossing the Schrödinger method encompasses multi-streaming and even virialization.

scholarly journals A Scalar Field Dark Matter Model and Its Role in the Large-Scale Structure Formation in the Universe

2012 ◽  
Vol 2012 ◽  
pp. 1-13 ◽  
Author(s):  
Mario A. Rodríguez-Meza
Keyword(s):  
Dark Matter ◽  
Scalar Field ◽  
Structure Formation ◽  
Large Scale ◽  
Large Scale Structure ◽  
Scale Structure ◽  
Matter Model ◽  
The Universe ◽  
Dark Matter Model ◽  
Large Scale Structure Formation

We present a model of dark matter based on scalar-tensor theory of gravity. With this scalar field dark matter model we study the non-linear evolution of the large-scale structures in the universe. The equations that govern the evolution of the scale factor of the universe are derived together with the appropriate Newtonian equations to follow the nonlinear evolution of the structures. Results are given in terms of the power spectrum that gives quantitative information on the large-scale structure formation. The initial conditions we have used are consistent with the so-called concordance ΛCDM model.

scholarly journals Of Cosmic Background Anisotropies

1996 ◽  
Vol 168 ◽  
pp. 31-44
Author(s):  
G.F. Smoot
Keyword(s):  
Large Scale ◽  
Thermal Emission ◽  
Big Bang ◽  
Microwave Background ◽  
The Standard Model ◽  
The Big Bang ◽  
The Universe ◽  
Fundamental Physical ◽  
Large Scale Structure Formation

Observations of the Cosmic Microwave Background (CMB) Radiation have put the standard model of cosmology, the Big Bang, on firm footing and provide tests of various ideas of large scale structure formation. CMB observations now let us test the role of gravity and General Relativity in cosmology including the geometry, topology, and dynamics of the Universe. Foreground galactic emissions, dust thermal emission and emission from energetic electrons, provide a serious limit to observations. Nevertheless, observations may determine if the evolution of the Universe can be understood from fundamental physical principles.

scholarly journals THE ROLE OF EDUCATIONAL SOCIETIES IN THE DEVELOPMENT OF EDUCATION IN ELISAVETGRAD REGION: SECOND HALF OF XIX–EARLY XX CENTURY

2020 ◽  
pp. 13-20
Author(s):  
Olena Olizko ◽  
Keyword(s):  
Large Scale ◽  
Significant Contribution ◽  
Public Library ◽  
Educational Work ◽  
Leading Role ◽  
Educational Processes ◽  
History Of ◽  
The Rich ◽  
The City

The article reveals the role of educational societies of Yelisavetgrad region in the development of education in the region in the second half of the XIX – early XX century. The purpose of the article is to reveal the role of educational societies of Yelisavetgrad region in the development of education in the region in the second half of the XIX – early XX century. The publication uses a historical-retrospective method, which allows for a retrospective analysis of the history of educational societies of Yelisavetgrad region in the period under study and highlight their contribution to the development of education in the region. It was found that a significant contribution to the development of educational processes in the Yelisavetgrad region in this period was made by educational societies opened on the initiative of progressive public figures of the city. Among the greatest achievements of Yelisavetgrad charity in providing various segments of the population with both basic and special knowledge is the rich and diverse activity of the Yelisavetgrad Society for Literacy and Crafts, which on a charitable basis carried out large-scale educational, pedagogical and educational work: progressive literature, conducted significant educational and organizational and advocacy work among the population and students of educational institutions, organized theater performances, concerts, art exhibitions. Through the efforts of the society, a home for young homeless children, the first kindergartens, a free public library-reading room and a public library were opened in the city. Active educational and propaganda activities of the members of the society played a leading role in the spread of education among various segments of the population, contributed to the development of schooling in the region. N. Braker, P. Ryabkov, M. Fedorovsky, V. Khartsiev and others made a significant contribution to reviving the work of the society.

scholarly journals On cosmology of interacting varying polytropic dark fluids

2019 ◽  
Vol 34 (17) ◽  
pp. 1950133
Author(s):  
Martiros Khurshudyan ◽  
Asatur Khurshudyan
Keyword(s):  
Dark Matter ◽  
Gravitational Lensing ◽  
Large Scale ◽  
Cold Dark Matter ◽  
Accelerated Expansion ◽  
Dark Side ◽  
Model Parameters ◽  
Special Role ◽  
Large Scale Universe

In this paper, a possibility of the accelerated expansion of the large scale universe with interacting varying polytropic fluid of a certain type is presented. About a special role of non-gravitational interactions between dark energy and dark matter, in particular, about a possibility of improvement and solution of problems arising in modern cosmology, has been discussed for a long time. This motivates us to consider new models, where non-gravitational interactions between varying polytropic fluid and cold dark matter are allowed. Mainly nonlinear interactions of a specific type is considered, found in recent literature. The present study extends previously obtained results demonstrating that considered new parameterization of dark side of the universe could be supported by available observational data and will present the role of considered non-gravitational interactions in this case. During the study of suggested cosmological models Om analysis is applied. Moreover, with different datasets, including a strong gravitational lensing dataset, the best fit values of the model parameters are obtained using [Formula: see text] analysis.

scholarly journals Surveying for Dwarf Galaxies Within Voids FN2 and FN8

2014 ◽  
Vol 11 (S308) ◽  
pp. 614-615
Author(s):  
Stephen McNeil ◽  
Chris Draper ◽  
J. Ward Moody
Keyword(s):  
Dark Matter ◽  
Galaxy Formation ◽  
Large Scale ◽  
Dwarf Galaxies ◽  
Low Density ◽  
Dark Matter Halos ◽  
Void Volumes ◽  
Four Square ◽  
Large Scale Structure Formation

AbstractThe presence or absence of dwarf galaxies with Mr' > -14 in low-density volumes correlates with dark matter halos and how they affect galaxy formation. We are conducting a redshifted Hα imaging survey for dwarf galaxies with Mr' > -13 in the heart of the well-defined voids FN2 and FN8 using the KPNO 4m Mayall telescope and Mosaic Imager. These data have furnished over 600 strong candidates in a four square degree area. Follow-up spectra finding none of these candidates to be within the void volumes will constrain the dwarf population there to be 2 to 8% of the cosmic mean. Conversely, finding even one Hα dwarf in the void heart will challenge several otherwise successful theories of large-scale structure formation.

Sign in / Sign up

Export Citation Format

Share Document