Halo Cores and Phase‐Space Densities: Observational Constraints on Dark Matter Physics and Structure Formation

2001 ◽  
Vol 561 (1) ◽  
pp. 35-45 ◽  
Author(s):  
Julianne J. Dalcanton ◽  
Craig J. Hogan
Keyword(s):  
Dark Matter ◽  
Phase Space ◽  
Structure Formation ◽  
Observational Constraints

scholarly journals An Origami Approximation to the Cosmic Web

2014 ◽  
Vol 11 (S308) ◽  
pp. 97-102 ◽  
Author(s):  
Mark C. Neyrinck
Keyword(s):  
Dark Matter ◽  
Phase Space ◽  
Structure Formation ◽  
Big Bang ◽  
Velocity Fields ◽  
Spin Correlations ◽  
Convex Polyhedral ◽  
Nearby Galaxies ◽  
The Big Bang ◽  
First Time

AbstractThe powerful Lagrangian view of structure formation was essentially introduced to cosmology by Zel'dovich. In the current cosmological paradigm, a dark-matter-sheet 3D manifold, inhabiting 6D position-velocity phase space, was flat (with vanishing velocity) at the big bang. Afterward, gravity stretched and bunched the sheet together in different places, forming a cosmic web when projected to the position coordinates.Here, I explain some properties of an origami approximation, in which the sheet does not stretch or contract (an assumption that is false in general), but is allowed to fold. Even without stretching, the sheet can form an idealized cosmic web, with convex polyhedral voids separated by straight walls and filaments, joined by convex polyhedral nodes. The nodes form in ‘polygonal’ or ‘polyhedral’ collapse, somewhat like spherical/ellipsoidal collapse, except incorporating simultaneous filament and wall formation. The origami approximation allows phase-space geometries of nodes, filaments, and walls to be more easily understood, and may aid in understanding spin correlations between nearby galaxies. This contribution explores kinematic origami-approximation models giving velocity fields for the first time.

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 INTERACTION BETWEEN DARK ENERGY AND DARK MATTER: OBSERVATIONAL CONSTRAINTS FROM OHD, BAO, CMB AND SNe Ia

2013 ◽  
Vol 22 (14) ◽  
pp. 1350082 ◽  
Author(s):  
SHUO CAO ◽  
NAN LIANG
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Observational Constraints ◽  
Coincidence Problem ◽  
Cosmological Constraints ◽  
Coincidence Index ◽  
Acceleration Of The Universe ◽  
Interaction Term ◽  
Negative Coupling ◽  
The Universe

In order to test if there is energy transfer between dark energy (DE) and dark matter (DM), we investigate cosmological constraints on two forms of nontrivial interaction between the DM sector and the sector responsible for the acceleration of the universe, in light of the newly revised observations including OHD, CMB, BAO and SNe Ia. More precisely, we find the same tendencies for both phenomenological forms of the interaction term Q = 3γHρ, i.e. the parameter γ to be a small number, |γ| ≈ 10-2. However, concerning the sign of the interaction parameter, we observe that γ > 0 when the interaction between dark sectors is proportional to the energy density of dust matter, whereas the negative coupling (γ < 0) is preferred by observations when the interaction term is proportional to DE density. We further discuss two possible explanations to this incompatibility and apply a quantitative criteria to judge the severity of the coincidence problem. Results suggest that the γm IDE model with a positive coupling may alleviate the coincidence problem, since its coincidence index C is smaller than that for the γd IDE model, the interacting quintessence and phantom models by four orders of magnitude.

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.

scholarly journals Decaying warm dark matter and structure formation

2018 ◽  
Vol 2018 (12) ◽  
pp. 026-026 ◽  
Author(s):  
Jui-Lin Kuo ◽  
Massimiliano Lattanzi ◽  
Kingman Cheung ◽  
José W.F. Valle
Keyword(s):  
Dark Matter ◽  
Structure Formation

scholarly journals NIHAO project II: halo shape, phase-space density and velocity distribution of dark matter in galaxy formation simulations

2016 ◽  
Vol 462 (1) ◽  
pp. 663-680 ◽  
Author(s):  
Iryna Butsky ◽  
Andrea V. Macciò ◽  
Aaron A. Dutton ◽  
Liang Wang ◽  
Aura Obreja ◽  
...  
Keyword(s):  
Dark Matter ◽  
Phase Space ◽  
Velocity Distribution ◽  
Galaxy Formation ◽  
Phase Space Density ◽  
Space Density

scholarly journals Braneworld model of dark matter: structure formation

2011 ◽  
Vol 44 (3) ◽  
pp. 581-601 ◽  
Author(s):  
Miguel A. García-Aspeitia ◽  
Juan A. Magaña ◽  
Tonatiuh Matos
Keyword(s):  
Dark Matter ◽  
Structure Formation ◽  
Braneworld Model

scholarly journals The holographic spacetime model of cosmology

2018 ◽  
Vol 27 (14) ◽  
pp. 1846005 ◽  
Author(s):  
Tom Banks ◽  
W. Fischler
Keyword(s):  
Dark Matter ◽  
Gravitational Waves ◽  
Structure Formation ◽  
Big Bang ◽  
Baryon Asymmetry ◽  
Gaussian Fluctuations ◽  
Primordial Gravitational Waves ◽  
Conventional Models ◽  
Non Gaussian ◽  
The Big Bang

This essay outlines the Holographic Spacetime (HST) theory of cosmology and its relation to conventional theories of inflation. The predictions of the theory are compatible with observations, and one must hope for data on primordial gravitational waves or non-Gaussian fluctuations to distinguish it from conventional models. The model predicts an early era of structure formation, prior to the Big Bang. Understanding the fate of those structures requires complicated simulations that have not yet been done. The result of those calculations might falsify the model, or might provide a very economical framework for explaining dark matter and the generation of the baryon asymmetry.

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