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We show that the nonlinear evolution of the cosmic gravitational clustering is approximately spatial local in the $x$-$k$ (position-scale) phase space if the initial perturbations are Gaussian. That is, if viewing the mass field with modes in the phase space, the nonlinear evolution will cause strong coupling among modes with different scale $k$, but at the same spatial area $x$, while the modes at different area $x$ remain uncorrelated, or very weakly correlated. We first study the quasi-local clustering behavior with the halo model, and demonstrate that the quasi-local evolution in the phase space is essentially due to the self-similar and hierarchical features of the cosmic gravitational clustering. The scaling of mass density profile of halos insures that the coupling between $(x-k)$ modes at different physical positions is substantially suppressed. Using high resolution N-body simulation samples in the LCDM model, we justify the quasi-locality with the correlation function between the DWT (discrete wavelet transform) variables of the cosmic mass field. Although the mass field underwent a highly non-linear evolution, and the DWT variables display significantly non-Gaussian features, there are almost no correlations among the DWT variables at different spatial positions. Possible applications of the quasi-locality have been discussed.
We investigate the weakly non-linear evolution of cosmic gravitational clustering in phase space by looking at the Zeldovich solution in the discrete wavelet transform (DWT) representation. We show that if the initial perturbations are Gaussian, the
We explore the evolution of halo spins in the cosmic web using a very large sample of dark matter haloes in the $Lambda$CDM Planck-Millennium N-body simulation. We use the NEXUS+ multiscale formalism to identify the hierarchy of filaments and sheets
The standard model of cosmology predicts the existence of cosmic neutrino background in the present Universe. To detect cosmic relic neutrinos in the vicinity of the Earth, it is necessary to evaluate the gravitational clustering effects on relic neu
We extend the local stellar galaxy-(sub)halo connection to the atomic hydrogen (HI) component by seeding semi-empirically galaxies into a large N-body dark matter (DM) simulation. The main input to construct the mock galaxy catalogue are: our constra
The causal limit usually considered in cosmology is the particle horizon, delimiting the possibilities of causal connection in the expanding universe. However it is not a realistic indicator of the effective local limits of important interactions in