66,207 research outputs found
Monte Carlo Study of the Spin-1 Baxter-Wu Model
The two-dimensional spin-1 Baxter-Wu model is studied by using Monte Carlo
simulations. The standard single-spin-flip Metropolis algorithm is used to
generate the configurations from which the order parameter, specific heat and
magnetic susceptibility are measured. The finite-size scaling procedure is
employed in order to get the critical behavior. The extensive simulations shown
that the critical exponents are different from those of the spin-1/2 model
suggesting that the spin-1 model is in a different universality class.Comment: 3 pages, 3 figures, 1 tabl
Cohomological characterization of vector bundles on multiprojective spaces
We show that Horrock's criterion for the splitting of vector bundles on
\PP^n can be extended to vector bundles on multiprojective spaces and to
smooth projective varieties with the weak CM property (see Definition 3.11). As
a main tool we use the theory of -blocks and Beilinson's type spectral
sequences. Cohomological characterizations of vector bundles are also showed
Building a Sample of Distant Clusters of Galaxies
Candidate clusters of galaxies drawn from the sample identified from the
moderately deep I-band data of the ESO Imaging Survey (EIS), have been used for
follow-up optical/infrared imaging and spectroscopic observations. The
observations were conducted to assess the nature of these candidates over a
large range of redshifts. Currently, 163 EIS candidates have (V-I) colors, 15
have (I-K) and 65 cluster fields have been observed spectroscopically. From a
preliminary analysis of these data, we find that > 65% of the candidates
studied show strong evidence of being real physical associations, over the
redshift range 0.2<z<1.1. The evidence in some cases comes directly from
spectroscopic measurements, in others indirectly from the detection of
overdensities of objects with either the same color or the same photometric
redshift, or from a combination of color and spectroscopic information.
Preliminary results also suggest that the redshift derived from the
matched-filter algorithm is a reasonable measure of the cluster's redshift,
possibly overestimating it by Delta z ~0.1, at least for systems at z<0.7.
Overdensities of red objects have been detected in over 100 candidates, 38 of
which with estimated redshifts >0.6, and six candidates in the interval
0.45<z<0.81 have either been identified directly from measured redshifts or
have been confirmed by the measurement of at least one redshift for galaxies
located along a red-sequence typical of cluster early-type galaxies. Lastly,
five candidates among those already observed in the infrared have (I-Ks) colors
consistent with them being in the redshift interval 0.8<z<1.1. The sample of
"confirmed" clusters, already the largest of its kind in the southern
hemisphere, will be further enlarged by ongoing observations.Comment: To appear in "Large Scale Structure in the X-ray Universe", ed. M.
Plionis and I. Georgantopoulos (Paris: Editions Frontieres), in pres
in a hot and dense medium
The behavior of and in hot strange quark matter in weak
equilibrium with temperature, is investigated within the SU(3)
Nambu-Jona-Lasinio [NJL] model. Possible manifestations of restoration of
symmetries, by temperature or density, in the behavior of and
are discussed. The role played by the combined effect of temperature and
density in the nature of the phase transition and meson behavior is also
analyzed.Comment: 15 pages, 5 figures. Contribution to the Second International
Workshop on Hadron Physics, Effective Theories of Low Energy QCD, 25-29
September, 2002 (Coimbra, Portugal
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