EMERGENCE OF FILAMENTARY STRUCTURE IN COSMOLOGICAL GRAVITATIONAL CLUSTERING

The morphological nature of structures that form under gravitational i nstability has been of central interest to cosmology for over two deca des. A remarkable feature of large-scale structures in the universe is that they occupy a relatively small fraction of the volume and yet sh ow coherence on scales comparable to the survey size. With the aid of a useful synthesis of percolation analysis and shape statistics we exp lore the evolution of morphology of isolated density clumps in real sp ace, and that of the cluster distribution as a whole, in scale-invaria nt cosmological models of gravitational instability. Our results, base d on an exhaustive statistical analysis, indicate that at finite densi ty thresholds one-dimensional filaments are more abundant than two-dim ensional sheets (pancakes) at most epochs and for all spectra, althoug h the first singularities could be pancake-like. Both filamentarity an d pancakeness of structures grow with time (in scale-free models this is equivalent to an increase in resolution), leading to the developmen t of a long coherence length scale in simulations.