5 research outputs found
The Topological Non-connectivity Threshold and magnetic phase transitions in classical anisotropic long-range interacting spin system
We analyze from the dynamical point of view the classical characteristics of
the Topological Non-connectivity Threshold (TNT), recently introduced in
F.Borgonovi, G.L.Celardo, M.Maianti, E.Pedersoli, J.Stat.Phys.,116,516(2004).
This shows interesting connections among Topology, Dynamics, and
Thermo-Statistics of ferro/paramagnetic phase transition in classical spin
systems, due to the combined effect of anisotropy and long-range interactions.Comment: 6 revtex pages, 4 .eps figures Contribution presented at the 3rd
Conference NEXT-Sigma-Phi News, Expectations, and Trends in Statistical
Physics, August 13-18 2005, Kolymbari, Crete. For related results see also
cond-mat/0402270 cond-mat/0410119 cond-mat/0505209 cond-mat/0506233
cond-mat/051007
A global descriptor of spatial pattern interaction in the galaxy distribution
We present the function J as a morphological descriptor for point patterns
formed by the distribution of galaxies in the Universe. This function was
recently introduced in the field of spatial statistics, and is based on the
nearest neighbor distribution and the void probability function. The J
descriptor allows to distinguish clustered (i.e. correlated) from ``regular''
(i.e. anti-correlated) point distributions. We outline the theoretical
foundations of the method, perform tests with a Matern cluster process as an
idealised model of galaxy clustering, and apply the descriptor to galaxies and
loose groups in the Perseus-Pisces Survey. A comparison with mock-samples
extracted from a mixed dark matter simulation shows that the J descriptor can
be profitably used to constrain (in this case reject) viable models of cosmic
structure formation.Comment: Significantly enhanced version, 14 pages, LaTeX using epsf, aaspp4, 7
eps-figures, accepted for publication in the Astrophysical Journa
Clustering of loose groups and galaxies from the Perseus--Pisces Survey
We investigate the clustering properties of loose groups in the
Perseus--Pisces redshift Survey (PPS). Previous analyses based on CfA and SSRS
surveys led to apparently contradictory results. We investigate the source of
such discrepancies, finding satisfactory explanations for them. Furthermore, we
find a definite signal of group clustering, whose amplitude exceeds the
amplitude of galaxy clustering (,
for the most significant case; distances are
measured in \hMpc). Groups are identified with the adaptive
Friends--Of--Friends (FOF) algorithms HG (Huchra \& Geller 1982) and NW
(Nolthenius \& White 1987), systematically varying all search parameters.
Correlation strenght is especially sensitive to the sky--link (increasing
for stricter normalization ), and to the (depth \mlim of the) galaxy
data. It is only moderately dependent on the galaxy luminosity function
, while it is almost insensitive to the redshift--link (both to
the normalization and to the scaling recipes HG or NW).Comment: 28 pages (LaTeX aasms4 style) + 5 Postscript figures ; ApJ submitted
on May 4th, 1996; group catalogs available upon request
([email protected]
A global descriptor of spatial pattern interaction in the galaxy distribution
We present the function J as a morphological descriptor for point patterns formed by the distribution of galaxies in the Universe. This function was recently introduced in the field of spatial statistics, and is based on the nearest neighbor distribution and the void probability function. The J descriptor allows to distinguish clustered (i.e. correlated) from âregular â (i.e. antiâcorrelated) point distributions. We outline the theoretical foundations of the method, perform tests with a MatĂ©rn cluster process as an idealised model of galaxy clustering, and apply the descriptor to galaxies and loose groups in the PerseusâPisces Survey. A comparison with mockâsamples extracted from a mixed dark matter simulation shows that the J descriptor can be profitably used to constrain (in this case reject) viable models of cosmic structure formation