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 THE STRUCTURE OF COLD DARK MATTER HALOS: RECENT INSIGHTS FROM HIGH RESOLUTION SIMULATIONS

2009 ◽  
Vol 24 (29) ◽  
pp. 2291-2305 ◽  
Author(s):  
MARCEL ZEMP
Keyword(s):  
Dark Matter ◽  
High Resolution ◽  
Structure Formation ◽  
Cold Dark Matter ◽  
Milky Way ◽  
Dark Matter Halos ◽  
General Properties

We review results from recent high resolution cosmological structure formation simulations, namely the Via Lactea I & II and GHALO projects. These simulations study the formation of Milky Way sized objects within a cosmological framework. We discuss the general properties of cold dark matter halos at redshift z = 0 and focus on new insights into the structure of halos we got due to the unprecedented high resolution in these simulations.

scholarly journals Gravitational Lens Statistics as a Probe of Halo Profiles

2004 ◽  
Vol 220 ◽  
pp. 143-144
Author(s):  
Masamune Oguri
Keyword(s):  
Dark Matter ◽  
Structure Formation ◽  
Density Profile ◽  
Time Delays ◽  
Large Scale ◽  
Cold Dark Matter ◽  
Gravitational Lens ◽  
Current Status ◽  
Formation Theory ◽  
Multiple Images

Recent development of the structure formation theory based on the cold dark matter scenario implies that a number of larger separation lensed quasars, for which a confirmed detection has not yet been achieved, will be observed in the ongoing large-scale surveys such as the 2dF survey and SDSS. We show that statistics of such large separation lenses can be a powerful probe of the density profile of dark halos. After we summarize the current status of the lens surveys in the 2dF and SDSS, we focus our discussion on what information can be extracted from these lens surveys. in addition, we also propose statistics of differential time delays between multiple images as an alternative probe of the density profile of dark halos.

scholarly journals STRUCTURE FORMATION WITH MIRROR DARK MATTER: CMB AND LSS

2005 ◽  
Vol 14 (01) ◽  
pp. 107-119 ◽  
Author(s):  
ZURAB BEREZHIANI ◽  
PAOLO CIARCELLUTI ◽  
DENIS COMELLI ◽  
FRANCESCO L. VILLANTE
Keyword(s):  
Dark Matter ◽  
Structure Formation ◽  
Large Scale ◽  
Cold Dark Matter ◽  
Big Bang ◽  
Dark Matter Candidate ◽  
Microwave Background ◽  
Quantitative Calculation ◽  
World Hypothesis ◽  
The Big Bang

In the mirror world hypothesis, the mirror baryonic component emerges as a possible dark matter candidate. An immediate question arises: how do the mirror baryons behave and what are their differences from the more familiar dark matter candidates such as cold dark matter? In this paper, we answer this question quantitatively. First, we discuss the dependence of the relevant scales for the structure formation (Jeans and Silk scales) on the two macroscopic parameters necessary to define the model: the temperature of the mirror plasma (limited by the Big Bang Nucleosynthesis) and the amount of mirror baryonic matter. Then we perform a complete quantitative calculation of the implications of mirror dark matter on the cosmic microwave background and large scale structure power spectrum. Finally, confronting with the present observational data, we obtain some bounds on the mirror parameter space.

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 Ab Initio Formation of Galaxies, Groups and Large-Scale Structure

2000 ◽  
Vol 174 ◽  
pp. 434-444
Author(s):  
Antonaldo Diaferio
Keyword(s):  
Dark Matter ◽  
Ab Initio ◽  
Structure Formation ◽  
Galaxy Formation ◽  
Large Scale ◽  
Cold Dark Matter ◽  
Global Properties ◽  
Small Scales ◽  
First Time ◽  
The Universe

AbstractFor the first time, the combination of semi-analytic modelling of galaxy formation and N-body simulations of cosmic structure formation enables us to model, at the same time, both the photometric and the clustering properties of galaxies. Two Cold Dark Matter Universes provide a reasonable fit to the observed properties of galaxies, groups and clusters, including luminosities, colours, density and velocity biases. We show how the properties of galaxies and groups on small scales are inextricably connected with the global properties of the Universe.

scholarly journals Shell-crossing in a ΛCDM Universe

2020 ◽  
Vol 501 (1) ◽  
pp. L71-L75
Author(s):  
Cornelius Rampf ◽  
Oliver Hahn
Keyword(s):  
Dark Matter ◽  
Perturbation Theory ◽  
Large Scale ◽  
Cold Dark Matter ◽  
Three Dimensional ◽  
Random Initial Data ◽  
Recursion Relations ◽  
Indispensable Tool ◽  
First Time ◽  
Very High

ABSTRACT Perturbation theory is an indispensable tool for studying the cosmic large-scale structure, and establishing its limits is therefore of utmost importance. One crucial limitation of perturbation theory is shell-crossing, which is the instance when cold-dark-matter trajectories intersect for the first time. We investigate Lagrangian perturbation theory (LPT) at very high orders in the vicinity of the first shell-crossing for random initial data in a realistic three-dimensional Universe. For this, we have numerically implemented the all-order recursion relations for the matter trajectories, from which the convergence of the LPT series at shell-crossing is established. Convergence studies performed at large orders reveal the nature of the convergence-limiting singularities. These singularities are not the well-known density singularities at shell-crossing but occur at later times when LPT already ceased to provide physically meaningful results.

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 Collisionless Dynamics and the Cosmic Web

2014 ◽  
Vol 11 (S308) ◽  
pp. 87-96
Author(s):  
Oliver Hahn
Keyword(s):  
Dark Matter ◽  
Structure Formation ◽  
Large Scale ◽  
Velocity Potential ◽  
Three Dimensional ◽  
Maximum Amount ◽  
Lagrangian Manifold ◽  
Linear Regime ◽  
Fine Grained ◽  
Simulation Techniques

AbstractI review the nature of three-dimensional collapse in the Zeldovich approximation, how it relates to the underlying nature of the three-dimensional Lagrangian manifold and naturally gives rise to a hierarchical structure formation scenario that progresses through collapse from voids to pancakes, filaments and then halos. I then discuss how variations of the Zeldovich approximation (based on the gravitational or the velocity potential) have been used to define classifications of the cosmic large-scale structure into dynamically distinct parts. Finally, I turn to recent efforts to devise new approaches relying on tessellations of the Lagrangian manifold to follow the fine-grained dynamics of the dark matter fluid into the highly non-linear regime and both extract the maximum amount of information from existing simulations as well as devise new simulation techniques for cold collisionless dynamics.

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