3,931 research outputs found
Responses of quark condensates to the chemical potential
The responses of quark condensates to the chemical potential, as a function
of temperature T and chemical potential \mu, are calculated within the
Nambu--Jona-Lasinio (NJL) model. We compare our results with those from the
recent lattice QCD simulations [QCD-TARO Collaboration, Nucl. Phys. B (Proc.
Suppl.) 106, 462 (2002)]. The NJL model and lattice calculations show
qualitatively similar behavior, and they will be complimentary ways to study
hadrons at finite density. The behavior above T_c requires more elaborated
analyses.Comment: 3 pages, 2 figs, based on a contribution to the Prof. Osamu Miyamura
memorial symposium, Hiroshima University, Nov. 16-17, 2001; slightly revised,
accepted for publication in Physical Review
A nonparametric empirical Bayes framework for large-scale multiple testing
We propose a flexible and identifiable version of the two-groups model,
motivated by hierarchical Bayes considerations, that features an empirical null
and a semiparametric mixture model for the non-null cases. We use a
computationally efficient predictive recursion marginal likelihood procedure to
estimate the model parameters, even the nonparametric mixing distribution. This
leads to a nonparametric empirical Bayes testing procedure, which we call
PRtest, based on thresholding the estimated local false discovery rates.
Simulations and real-data examples demonstrate that, compared to existing
approaches, PRtest's careful handling of the non-null density can give a much
better fit in the tails of the mixture distribution which, in turn, can lead to
more realistic conclusions.Comment: 18 pages, 4 figures, 3 table
The Matter and the Pseudoscalar Densities in Lattice QCD
The matter and the pseudoscalar densities inside a hadron are calculated via
gauge-invariant equal-time correlation functions. A comparison is made between
the charge charge and the matter density distributions for the pion, the rho,
the nucleon and the within the quenched theory, and with two
flavours of dynamical quarks.Comment: Typos corrected; 13 pages, 16 figure
Excited nucleon spectrum from lattice QCD with maximum entropy method
We study excited states of the nucleon in quenched lattice QCD with the
spectral analysis using the maximum entropy method. Our simulations are
performed on three lattice sizes , and
, at to address the finite volume issue. We find a
significant finite volume effect on the mass of the Roper resonance for light
quark masses. After removing this systematic error, its mass becomes
considerably reduced toward the direction to solve the level order puzzle
between the Roper resonance and the negative-parity nucleon
.Comment: Lattice2003(spectrum), 3 pages, 4 figure
Topological Test Spaces
A test space is the set of outcome-sets associated with a collection of
experiments. This notion provides a simple mathematical framework for the study
of probabilistic theories -- notably, quantum mechanics -- in which one is
faced with incommensurable random quantities. In the case of quantum mechanics,
the relevant test space, the set of orthonormal bases of a Hilbert space,
carries significant topological structure. This paper inaugurates a general
study of topological test spaces. Among other things, we show that any
topological test space with a compact space of outcomes is of finite rank. We
also generalize results of Meyer and Clifton-Kent by showing that, under very
weak assumptions, any second-countable topological test space contains a dense
semi-classical test space.Comment: 12 pp., LaTeX 2e. To appear in Int. J. Theor. Phy
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