A test of the adhesion approximation for gravitational clustering

We quantitatively compare a particle implementation of the adhesionapproximation to fully non--linear, numerical nbody simulations. Our primarytool, cross--correlation of nbody simulations with the adhesion approximation,indicates good agreement, better than that found by the same test performedwith the Zel'dovich approximation (hereafter ZA). However, thecross--correlation is not as good as that of the truncated Zel'dovichapproximation (TZA), obtained by applying the Zel'dovich approximation aftersmoothing the initial density field with a Gaussian filter. We confirm that theadhesion approximation produces an excessively filamentary distribution.Relative to the nbody results, we also find that: (a) the power spectrumobtained from the adhesion approximation is more accurate than that from ZA orTZA, (b) the error in the phase angle of Fourier components is worse than thatfrom TZA, and (c) the mass distribution function is more accurate than thatfrom ZA or TZA. It appears that adhesion performs well statistically, but thatTZA is more accurate dynamically, in the sense of moving mass to the rightplace. Subject Heading: Galaxies, formation, clustering--large--scale structure ofthe UniverseComment: TeX, 7 pages excluding figures (contact melott@kusmos.phsx.ukans.edu). submitted to Ap