14,659 research outputs found
Temporal correlator in YM^2_3 and reflection-positivity violation
We consider numerical data for the lattice Landau gluon propagator obtained
at very large lattice volumes in three-dimensional pure SU(2) Yang-Mills gauge
theory (YM^2_3). We find that the temporal correlator C(t) shows an oscillatory
pattern and is negative for several values of t. This is an explicit violation
of reflection positivity and can be related to gluon confinement. We also
obtain a good fit for this quantity in the whole time interval using a sum of
Stingl-like propagators.Comment: 3 pages, 1 figure, 1 table, presented by A.R. Taurines at the IX
Hadron Physics and VII Relativistic Aspects of Nuclear Physics Workshops,
Angra dos Reis, Rio de Janeiro, Brazil (March 28--April 3, 2004
Symbolic Sequences and Tsallis Entropy
We address this work to investigate symbolic sequences with long-range
correlations by using computational simulation. We analyze sequences with two,
three and four symbols that could be repeated times, with the probability
distribution . For these sequences, we verified that
the usual entropy increases more slowly when the symbols are correlated and the
Tsallis entropy exhibits, for a suitable choice of , a linear behavior. We
also study the chain as a random walk-like process and observe a nonusual
diffusive behavior depending on the values of the parameter .Comment: Published in the Brazilian Journal of Physic
Effects of Nonperturbative Improvement in Quenched Hadron Spectroscopy
We discuss a comparative analysis of unimproved and nonperturbatively
improved quenched hadron spectroscopy, on a set of 104 gauge configurations, at
beta=6.2. We also present here our results for meson decay constants, including
the constants f_D and f_Ds in the charm-quark region.Comment: LATTICE98(spectrum
Non-Perturbatively Improved Quenched Hadron Spectroscopy
We make a quenched lattice simulation of hadron spectroscopy at beta=6.2 with
the Wilson action non-perturbatively improved. With respect to the unimproved
case, the estimate of the lattice spacing is less influenced by the choice of
input hadron masses. We study also the effects of using an improved quark mass
in the fits to the dependence of hadron masses upon quark masses.Comment: 12 pages, including 5 postscript figure
Long Memory and Volatility Clustering: is the empirical evidence consistent across stock markets?
Long memory and volatility clustering are two stylized facts frequently
related to financial markets. Traditionally, these phenomena have been studied
based on conditionally heteroscedastic models like ARCH, GARCH, IGARCH and
FIGARCH, inter alia. One advantage of these models is their ability to capture
nonlinear dynamics. Another interesting manner to study the volatility
phenomena is by using measures based on the concept of entropy. In this paper
we investigate the long memory and volatility clustering for the SP 500, NASDAQ
100 and Stoxx 50 indexes in order to compare the US and European Markets.
Additionally, we compare the results from conditionally heteroscedastic models
with those from the entropy measures. In the latter, we examine Shannon
entropy, Renyi entropy and Tsallis entropy. The results corroborate the
previous evidence of nonlinear dynamics in the time series considered.Comment: 8 pages; 2 figures; paper presented in APFA 6 conferenc
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