scholarly journals COSMIC STRINGS, LOOPS, AND LINEAR GROWTH OF MATTER PERTURBATIONS

2002 ◽  
Vol 11 (01) ◽  
pp. 61-102 ◽  
Author(s):  
JIUN-HUEI PROTY WU ◽  
PEDRO P. AVELINO ◽  
E. P. S. SHELLARD ◽  
BRUCE ALLEN
Keyword(s):  
Dark Matter ◽  
Structure Formation ◽  
Cosmic String ◽  
Cold Dark Matter ◽  
Cosmic Strings ◽  
Topological Analysis ◽  
Long Strings ◽  
Source Spectrum ◽  
Galaxy Surveys ◽  
Network Properties

We describe a detailed study of string-seeded structure formation using high resolution numerical simulations in open universes and those with a non-zero cosmological constant. We provide a semi-analytical model which can reproduce these simulation results including the effect from small loops chopped of by the string network. A detailed study of cosmic string network properties regarding structure formation is also given, including the correlation time, the topological analysis of the source spectrum, the correlation between long strings and loops, and the evolution of long-string and loop energy densities. For models with Γ=Ω h=0.1 -0.2 and a cold dark matter background, we show that the linear density fluctuation power spectrum induced by cosmic strings has both an amplitude at 8 h-1 Mpc, σ8, and an overall shape which are consistent within uncertainties with those currently inferred from galaxy surveys. The cosmic string scenario with hot dark matter requires a strongly scale-dependent bias in order to agree with observations.

First Structure Formation. II. Cosmic String plus Hot Dark Matter Models

1998 ◽  
Vol 508 (2) ◽  
pp. 530-534 ◽  
Author(s):  
Tom Abel ◽  
Albert Stebbins ◽  
Peter Anninos ◽  
Michael L. Norman
Keyword(s):  
Dark Matter ◽  
Structure Formation ◽  
Cosmic String

scholarly journals Impact of dark matter models on the EoR 21-cm signal bispectrum

2020 ◽  
Vol 497 (3) ◽  
pp. 2941-2953 ◽  
Author(s):  
Anchal Saxena ◽  
Suman Majumdar ◽  
Mohd Kamran ◽  
Matteo Viel
Keyword(s):  
Dark Matter ◽  
Structure Formation ◽  
Cold Dark Matter ◽  
Power Spectra ◽  
Neutral Hydrogen ◽  
Cosmic Time ◽  
Lower Number ◽  
Neutral Fraction ◽  
Small Scales ◽  
Low Mass

ABSTRACT The nature of dark matter sets the timeline for the formation of first collapsed haloes and thus affects the sources of reionization. Here, we consider two different models of dark matter: cold dark matter (CDM) and thermal warm dark matter (WDM), and study how they impact the epoch of reionization (EoR) and its 21-cm observables. Using a suite of simulations, we find that in WDM scenarios, the structure formation on small scales gets suppressed, resulting in a smaller number of low-mass dark matter haloes compared to the CDM scenario. Assuming that the efficiency of sources in producing ionizing photons remains the same, this leads to a lower number of total ionizing photons produced at any given cosmic time, thus causing a delay in the reionization process. We also find visual differences in the neutral hydrogen (H i) topology and in 21-cm maps in case of the WDM compared to the CDM. However, differences in the 21-cm power spectra, at the same neutral fraction, are found to be small. Thus, we focus on the non-Gaussianity in the EoR 21-cm signal, quantified through its bispectrum. We find that the 21-cm bispectra (driven by the H i topology) are significantly different in WDM models compared to the CDM, even for the same mass-averaged neutral fractions. This establishes that the 21-cm bispectrum is a unique and promising way to differentiate between dark matter models, and can be used to constrain the nature of the dark matter in the future EoR observations.

scholarly journals Small-scale Substructure in Dark Matter Haloes: Where Does Galaxy Formation Come to an End?

2004 ◽  
Vol 220 ◽  
pp. 91-98 ◽  
Author(s):  
J. E. Taylor ◽  
J. Silk ◽  
A. Babul
Keyword(s):  
Dark Matter ◽  
Power Spectrum ◽  
Structure Formation ◽  
Galaxy Formation ◽  
Cold Dark Matter ◽  
High Redshift ◽  
Small Scale ◽  
Analytic Model ◽  
Model Predictions ◽  
Low Mass

Models of structure formation based on cold dark matter predict that most of the small dark matter haloes that first formed at high redshift would have merged into larger systems by the present epoch. Substructure in present-day haloes preserves the remains of these ancient systems, providing the only direct information we may ever have about the low-mass end of the power spectrum. We describe some recent attempts to model halo substructure down to very small masses, using a semi-analytic model of halo formation. We make a preliminary comparison between the model predictions, observations of substructure in lensed systems, and the properties of local satellite galaxies.

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 FORMATION OF WAKES BY CHIRAL CONDUCTING COSMIC STRINGS

2004 ◽  
Vol 19 (32) ◽  
pp. 2445-2450 ◽  
Author(s):  
M. C. B. ABDALLA ◽  
A. A. BYTSENKO ◽  
M. E. X. GUIMARÃES
Keyword(s):  
Dark Matter ◽  
Cold Dark Matter ◽  
Cosmic Strings ◽  
Formation And Evolution

Chiral cosmic strings are naturally produced at the end of D-term inflation and they present very interesting cosmological consequences. In this work, we investigate the formation and evolution of wakes by a chiral string. We show that, for cold dark matter, the mechanism of forming wakes by a chiral string is similar to the mechanism by an ordinary string.

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 COSMOLOGY WITH MIRROR DARK MATTER I: LINEAR EVOLUTION OF PERTURBATIONS

2005 ◽  
Vol 14 (02) ◽  
pp. 187-221 ◽  
Author(s):  
PAOLO CIARCELLUTI
Keyword(s):  
Dark Matter ◽  
Structure Formation ◽  
Cold Dark Matter ◽  
Linear Structure ◽  
Numerical Code ◽  
Linear Regime ◽  
Fundamental Parameters ◽  
Linear Evolution ◽  
Baryonic Density ◽  
The Difference

This is the first paper of a series devoted to the study of the cosmological implications of the parallel mirror world with the same microphysics as the ordinary one, but having smaller temperature, with a limit set by the BBN constraints. The difference in temperature of the ordinary and mirror sectors generates shifts in the key epochs for structure formation, which proceeds in the mirror sector under different conditions. We consider adiabatic scalar primordial perturbations as an input and analyze the trends of all the relevant scales for structure formation (Jeans length and mass, Silk scale, horizon scale) for both ordinary and mirror sectors, comparing them with the CDM case. These scales are functions of the fundamental parameters of the theory (the temperature of the mirror plasma and the amount of mirror baryonic matter), and in particular they are influenced by the difference between the cosmological key epochs in the two sectors. Then we use a numerical code to compute the evolution in linear regime of density perturbations for all the components of a Mirror Universe: ordinary baryons and photons, mirror baryons and photons, and possibly cold dark matter. We analyze the evolution of the perturbations for different values of mirror temperature and baryonic density, and obtain that for x=T′/T less than a typical value x eq , for which the mirror baryon–photon decoupling happens before the matter–radiation equality, mirror baryons are equivalent to the CDM for the linear structure formation process. Indeed, the smaller the value of x, the closer mirror dark matter resembles standard cold dark matter during the linear regime.

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 Formation Mechanism of Hierarchical Astronomical Objects in the Cosmic String Scheme

1999 ◽  
Vol 183 ◽  
pp. 249-249
Author(s):  
Tetsuya Hara ◽  
Sigeru Miyoshi ◽  
Petri Mähönen
Keyword(s):  
Dark Matter ◽  
Formation Mechanism ◽  
Cosmic String ◽  
Cold Dark Matter ◽  
Block Size ◽  
Line Density ◽  
Overlapped Region

Because of the angular deficit around cosmic string, cold dark matter(CDM) gets the velocity toward the plane of moving string and wake is formed there. It means that CDM body is cut by string, two blocks move each other, and the overlapped region becomes wake. The wake and/or block size is determined by the horizon size at zi when the wake is triggered by the string. The nonlinearity and/or thickness of the wake depends on the moving length of CDM toward the wake which depends on zi, the line density and velocity of string.

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