Ellipsoidal Collapse and Previrialization

Popolo, A. Del; Ercan, E. N.; Xia, Zicheng

doi:10.1086/321137

Cited by 47 publications

(42 citation statements)

References 40 publications

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“…This result is in agreement with Peebles (1990). The quoted controversy was addressed by Del Popolo et al (2001) who examined the evolution of non-spherical inhomogeneities in a Einstein-de Sitter universe, by numerically solving the equations of motion for the principal axes and the density of a dust ellipsoid. They showed that for lower values of ν (ν = 2) the growth rate enhancement of the density contrast induced by the shear is counterbalanced by the effect of angular momentum acquisition.…”

Section: Introductionsupporting

confidence: 71%

Some improvements to the spherical collapse model

Popolo¹

2006

A&A

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I study the joint effect of dynamical friction, tidal torques and cosmological constant on clusters of galaxies formation. I show that within high-density environments, such as rich clusters of galaxies, both dynamical friction and tidal torques slows down the collapse of low-ν peaks producing an observable variation in the time of collapse of the perturbation and, as a consequence, a reduction in the mass bound to the collapsed perturbation. Moreover, the delay of the collapse produces a tendency for less dense regions to accrete less mass, with respect to a classical spherical model, inducing a biasing of over-dense regions toward higher mass. I show how the threshold of collapse is modified if dynamical friction, tidal torques and a non-zero cosmological constant are taken into account and I use the Extended Press Schecter (EPS) approach to calculate the effects on the mass function. Then, I compare the numerical mass function given in Reed et al. (2003) with the theoretical mass function obtained in the present paper. I show that the barrier obtained in the present paper gives rise to a better description of the mass function evolution with respect to other previous models (Sheth &

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Section: Introductionsupporting

confidence: 71%

Some improvements to the spherical collapse model

Popolo¹

2006

A&A

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“…However, the description of matter as a pressureless ideal fluid will break down on small scales when non-linear structures form, due to shell-crossing. After any vorticity is generated in gravitational collapse [107], it will be amplified by the collapse, and will formally diverge at the same time as the density [108]. A static dust structure, with θ = 0, is possible only if large amounts of vorticity are present, as (2) shows: vorticity has to balance the contribution of both the energy density and the shear on the right-hand side.…”

Section: The Local Equationsmentioning

confidence: 99%

Evaluating backreaction with the peak model of structure formation

Räsänen

2008

J. Cosmol. Astropart. Phys.

174

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Abstract.We evaluate the average expansion rate of a universe which contains a realistic evolving ensemble of non-linear structures. We use the peak model of structure formation to obtain the number density of structures, and take the individual structures to be spherical. The expansion rate increases relative to the FRW value on a timescale of 10-100 billion years, because the universe becomes dominated by fast-expanding voids. However, the increase is not rapid enough to correspond to acceleration. We discuss how to improve our treatment. We also consider various qualitative issues related to backreaction.PACS numbers: 04.40. Nr, 95.36.+x, 98.80.Jk Evaluating backreaction with the peak model of structure formation 1

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“…However, before we can make use of such a formula, we must relate the statistical quantities and h() to and h SC (). It is well known that (Padmanabhan 1996(Padmanabhan , 2002Peebles 1980;Padmanabhan & Engineer 1998;Del Popolo et al 2001;Padmanabhan & Ray 2006), on scales smaller than the size of the collapsing objects and around high density peaks,…”

Section: Modeling Nonlinear Structuresmentioning

confidence: 99%

An Improved Semianalytical Spherical Collapse Model for Nonlinear Density Evolution

Shaw

Mota

2008

ASTROPHYS J SUPPL S

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We derive a semianalytical extension of the spherical collapse model of structure formation that takes account of the effects of deviations from spherical symmetry and shell crossing, which are important in the nonlinear regime. Our model is designed so that it predicts a relation between the peculiar velocity and density contrast that agrees with the results of N-body simulations in the region where such a comparison can sensibly be made. Prior to turnaround, when the unmodified spherical collapse model is expected to be a good approximation, the predictions of the two models coincide almost exactly. The effects of a late time dominating dark energy component are also taken into account. The improved spherical collapse model is a useful tool when one requires a good approximation not just to the evolution of the density contrast but also its trajectory. Moreover, the analytical fitting formulae presented is simple enough to be used anywhere where the standard spherical collapse might be used but with the advantage that it includes a realistic model of the effects of virialisation.

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Ellipsoidal Collapse and Previrialization

Cited by 47 publications

References 40 publications

Some improvements to the spherical collapse model

Some improvements to the spherical collapse model

Evaluating backreaction with the peak model of structure formation

An Improved Semianalytical Spherical Collapse Model for Nonlinear Density Evolution

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