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Session 86 - Cosmology: Theory.
Display session, Friday, January 09
Exhibit Hall,

[86.06] Measuring the Network Structure in Simulations and Observations

S. F. Shandarin (U. Kansas)

Redshift surveys reveal the spectacular abundance of structures in the spatial galaxy distribution. The filamentary and pancake-like superclusters of galaxies are linked into a huge network spanning through the entire universe. Measuring such a patterns was a challenge to theorists for many years. Using percolation statistics we, for the first time, demonstrate the universal character of a network pattern in the real space, mass distributions resulting from nonlinear gravitational instability of initial Gaussian fluctuations. Percolation analysis of five stages of the nonlinear evolution of five power law models (P(k) \propto k^n with n=+3, +1, 0, -1, and -2 in an Ømega =1 universe) reveals that all models show a shift toward a network topology if seen with high enough resolution. However, quantitatively, the shift is significantly different in different models: the smaller the spectral index n the stronger the shift.

We also employ a percolation technique developed for pointwise distributions to analyze two-dimensional projections of the three northern and three southern slices in the Las Campanas Redshift Survey. As a major result we report a measurement of an unambiguous signal, with high signal-to-noise ratio (at least at a few \sigmas level), indicating significantly stronger connectivity of the galaxy distribution which in two dimensions is indicative of a filamentary distribution. This is in general agreement with the visual impression and typical for the standard theory of the large-scale structure formation based on gravitational instability of initially Gaussian density fluctuations.

Program listing for Friday