IUCAA Preprints

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    Morphology of clusters and superclusters in N-body simulations of cosmological gravitational clustering
    (2015-03-13) Sathyaprakash, B.S.; Sahni, Varun; Shandarian, Sergei
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    Modelling the nonlinear gravitational clustering in the expanding universe
    (2015-01-25) Padmanabhan, T.
    The gravitational clustering of collisionless particles in an expanding universe is modelled using some simple physical ideas. I show that it is indeed possible to understand the nonlinear clustering in terms of three well defined regimes: (1) linear regime (2) quasilinear regime which is dominated by scale-invariant radial infall and (3) nonlinear regime dominated by nonradial motions and mergers. Modelling each of these regimes separately I show how the nonlinear two point correlation function can be related to the linear correlation function in heirarchical models. This analysis leads to results which are in good agreement with numerical simulations thereby providing an explanation for numerical results. The ideas presented here will also serve as a powerful anlytical tool to investigate nonlinear clustering in different models. Several implications of the result are discussed.
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    A new indicator of nonlinear gravitational clustering
    (2015-01-25) Bagla, J. S.
    Alignment of velocity and acceleration before shell crossing, and later misalignment are used to define velocity contrast, an indicator of dynamical state of matter undergoing gravitational collapse. We use this study bias in clustering properties of dynamically nonlinear mass.
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    Entropy changes in the clustering of galaxies in an expanding universe
    (2011-05-26) Iqbal, Naseer; Khan, Mohammad Shafi; Masood, Tabasum
    In the present work the approach-thermody-namics and statistical mechanics of gravitating systems is applied to study the entropy changein gravitational clustering of galaxies in an ex-panding universe. We derive analytically the expressions for gravitational entropy in terms of temperature T and average density n of the par-ticles (galaxies) in the given phase space cell. It is found that during the initial stage of cluster-ing of galaxies, the entropy decreases and finally seems to be increasing when the system attains virial equilibrium. The entropy changes are studied for different range of measuring correlation parameter b. We attempt to provide a clearer account of this phenomena. The entropy esults for a system consisting of extended mass (non-point mass) particles show a imilar behaviour with that of point mass particles clustering gravitationally in an expanding uni-verse.