Gravitational clustering of Gaussian density fluctuations and the origin of hierarchy correlations

1991 ◽  
Vol 376 ◽  
pp. L5 ◽  
Author(s):  
A. Kashlinsky
Keyword(s):  
Density Fluctuations ◽  
Gravitational Clustering ◽  
Gaussian Density

scholarly journals Gaussian density fluctuations and mode coupling theory for supercooled liquids

2001 ◽  
Vol 55 (2) ◽  
pp. 157-163 ◽  
Author(s):  
E Zaccarelli ◽  
G Foffi ◽  
F Sciortino ◽  
P Tartaglia ◽  
K. A Dawson
Keyword(s):  
Mode Coupling ◽  
Supercooled Liquids ◽  
Density Fluctuations ◽  
Coupling Theory ◽  
Mode Coupling Theory ◽  
Gaussian Density

scholarly journals Galaxy Formation: Confrontation with Observations

1987 ◽  
Vol 124 ◽  
pp. 391-413
Author(s):  
Joseph Silk
Keyword(s):  
Dark Matter ◽  
Star Formation ◽  
Galaxy Formation ◽  
Cold Dark Matter ◽  
Dwarf Galaxies ◽  
Density Fluctuations ◽  
Inflationary Cosmology ◽  
Lyman Alpha ◽  
Gaussian Density

The implications for galaxy formation of inflationary cosmology are reviewed. In particular, I explore some implications of the hypothesis that galaxies form from adiabatic, gaussian density fluctuations in a cold dark matter–dominated universe. Topics discussed include protogalaxies and the epoch of galaxy formation, Lyman alpha clouds, dark halos and dwarf galaxies. Finally I describe how environmental biasing may arise as a consequence of tidally induced star formation in protoclusters.

scholarly journals Theories of Large Scale Structure

1988 ◽  
Vol 130 ◽  
pp. 273-280
Author(s):  
S. F. Shandarin
Keyword(s):  
Large Scale ◽  
Gravitational Instability ◽  
Large Scale Structure ◽  
Density Fluctuations ◽  
Weakly Interacting Massive Particles ◽  
Scale Structure ◽  
Main Process ◽  
Inflationary Model ◽  
Important Class ◽  
Gaussian Density

This talk is concerned with one of the most important class of theories of Large Scale Structure (hereafter LSS) based on two principal assumptions. It is supposed that (i) the main process is gravitational instability in expanding universe and (ii) the primordial perturbations a r e small Gaussian density fluctuations. Both assumptions are natural in inflationary model of the very early universe as well as in cosmological models dominated by Dark Matter (DM) in the form of Weakly Interacting Massive Particles (WIMPs). Other possible models of LSS formation are discussed by N. Turok, J. Ostriker and A. Dekel.

Propagation and stability of vorticity–entropy waves in a non-uniform flow

2007 ◽  
Vol 575 ◽  
pp. 149-176 ◽  
Author(s):  
O. V. ATASSI
Keyword(s):  
Velocity Profile ◽  
Density Profile ◽  
Axial Velocity ◽  
Density Fluctuations ◽  
Flow Profile ◽  
Density Gradients ◽  
Mean Flow ◽  
Mean Velocity ◽  
Gaussian Density ◽  
The Mean

The evolution of disturbances in an annular duct with a non-isentropic radially varying mean flow is studied. Linear and nonlinear analyses are carried out to examine how the mean velocity and density gradients affect the stability and coupling between the disturbances. To isolate the effect of the mean-velocity gradients from that of the mean-density gradients two mean flows are considered, one with a Gaussian density profile and a uniform axial velocity and the other with Gaussian density and Gaussian axial-velocity distributions. For small-amplitude disturbances with the former mean flow profile, the vortical disturbances convect with the mean flow and density fluctuations grow linearly in space as a result of the interaction of the mean-density gradient with the disturbance radial velocity. Eigenmode analysis of the latter profile shows that unstable modes with exponential growth occur owing to the inflection point in the mean-velocity profile. These modes are almost independent of the mean-density profile and are most unstable for low azimuthal wavenumbers. Nonlinear solutions support the linear results and show an algebraic growth of the density for a range of azimuthal wavenumbers and both uniform and non-uniform mean-velocity profiles. The growth of the velocity fluctuations, however, is strongly dependent on the azimuthal wavenumber of the incident disturbance and the mean-velocity profile. The largest growth in the disturbance is observed at radial locations where the largest mean-flow gradients exist. Owing to the growth of the density fluctuations, coupled vorticity–entropy waves are observed downstream of a forced harmonic excitation in a non-isentropic flow. The forcing amplitudes of the incident waves were varied to see how the solutions change with amplitude. As the amplitude is increased, the waves continue to grow and a steepening of the gradients is observed as they propagate downstream until eventually very sharp density and velocity fronts form. These results show that the mean-flow and density profiles play an important role in the evolution of low-azimuthal-wavenumber disturbances which can couple strongly to the duct acoustic modes during combustion instabilities.

scholarly journals Constraints on the Biasing of Density Fluctuations

1988 ◽  
Vol 130 ◽  
pp. 163-167
Author(s):  
Alexander S. Szalay
Keyword(s):  
Functional Form ◽  
Nonlinear Function ◽  
Density Fluctuations ◽  
Gaussian Field ◽  
Hermite Expansion ◽  
Galaxy Distribution ◽  
Gaussian Density ◽  
The Galaxy ◽  
Amplification Mechanism ◽  
Scaling Coefficient

A general nonlinear function G(X) describing the biasing of primordial Gaussian density fluctuations is considered. Arbitrary N-point correlations of the biased field are calculated in the form of a series expansion in terms of the correlations of the Gaussian field. The observed scaling of the three point correlations in the galaxy distribution is satisfied, but the scaling coefficient Q has a nontrivial value Q = J2/J12, where Jk is the k-th term in the Hermite expansion of G(X). The three point function is always accompanied by a cubic term Q3ξ1ξ2ξ3, independent of the functional form of the biasing. Its absence in the cluster 3-point correlations may be observable, in which case it rules out biasing as the major amplification mechanism of galaxy and cluster correlations.

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