2,944 research outputs found
HBT Effect Based on a Hydrodynamical Model
We investigate HBT radii based on the numerical solutions of the
hydrodynamical model which are so tuned as to reproduce the recent experimental
data at the CERN SPS. Comparing the sizes of freeze-out hypersurface with HBT
radii, we discuss dynamical effect of the systematic flow on the apparent HBT
radii. Finally we compare HBT radii of the QGP phase transition model with
those of the hadron gas model without phase transition.Comment: 5 pages, LaTeX, 7 EPS figures. Talk at the International School on
the Physics of Quark Gluon Plasma, June 3-6, 1997, Hiroshima, Japa
Various Approaches to Cosmological Gravitational Lensing in Inhomogeneous Models
Gravitational lensing of distant objects caused by gravitational tidal forces
from inhomogeneities in the universe is weak in most cases, but it is noticed
that it gives a great deal of information about the universe, especially
regarding the distribution of dark matter. The statistical values of optical
quantities such as convergence, amplification and shear have been derived by
many people using various approaches, which include the linear perturbational
treatment in the weak limit and the nonlinear treatment considering small-scale
matter distribution.
In this review paper we compare the following three main approaches: (a) the
approach in the multi-lens-plane theory; (b) the approach due to the direct
integration method; and (c) the perturbational approach.
In the former two approaches inhomogeneous matter distributions are produced
in the CDM model using -body simulations (the PM code and the tree-code,
respectively). In (c) the power spectrum corresponding to the CDM model is used
for the large-scale matter distribution.Comment: 30 pages, 13 figure
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