143 research outputs found
Probability of false negative results in GSR detection: a Bayesian approach
We calculated the probability of obtaining false negative results in GSR
detection depending on the resolution setup for sample scanning, in order to
quantitatively describe the trade-off between low false negative rates in the
detection of characteristic particles and the effort that measurements entail.
We built and validated a GSR particle detection model that associates particle
size with equipment registers, and we applied it to samples analyzed by a
forensic science laboratory. Our results indicate that the probability of a
false negative, i.e. a result where all characteristic particles in a sample
which go undetected, is below 5\% for pixel sizes below . These
results indicate that pixel sizes as great as the double that is commonly used
in usual laboratory casework are effective for an initial scanning of a sample
as it yields good rates of detection of characteristic particles, which might
exponentially reduce laboratory workload.Comment: preprint, 14 pages, 8 figure
The water supercooled regime as described by four common water models
The temperature scale of simple water models in general does not coincide
with the natural one. Therefore, in order to make a meaningful evaluation of
different water models a temperature rescaling is necessary. In this paper we
introduce a rescaling using the melting temperature and the temperature
corresponding to the maximum of the heat capacity to evaluate four common water
models (TIP4P-Ew, TIP4P-2005, TIP5P-Ew and Six-Sites) in the supercooled
regime. Although all the models show the same general qualitative behavior, the
TIP5P-Ew appears as the best representation of the supercooled regime when the
rescaled temperature is used. We also analyze, using thermodynamic arguments,
the critical nucleus size for ice growth. Finally, we speculate on the possible
reasons why atomistic models do not usually crystalize while the coarse grained
mW model do crystallize.Comment: 8 pages, 8 figure
Symmetry Operators and Separation of Variables for Dirac's Equation on Two-Dimensional Spin Manifolds
A signature independent formalism is created and utilized to determine the
general second-order symmetry operators for Dirac's equation on two-dimensional
Lorentzian spin manifolds. The formalism is used to characterize the
orthonormal frames and metrics that permit the solution of Dirac's equation by
separation of variables in the case where a second-order symmetry operator
underlies the separation. Separation of variables in complex variables on
two-dimensional Minkowski space is also considered.Comment: This paper is dedicated to Professor Willard Miller, Jr. on the
occasion of his retirement from the School of Mathematics at the University
of Minnesot
How large is "large " for Nuclear matter?
We argue that a so far neglected dimensionless scale, the number of neighbors
in a closely packed system, is relevant for the convergence of the large
expansion at high chemical potential. It is only when the number of colors is
large w.r.t. this new scale (\sim \order{10}) that a convergent large
limit is reached. This provides an explanation as to why the large
expansion, qualitatively successful in in vacuum QCD, fails to describe high
baryo-chemical potential systems, such as nuclear matter. It also means that
phenomenological claims about high density matter based on large
extrapolations should be treated with caution.Comment: Proceedings of CPOD2010 conference, in Dubna. Results based on
Phys.Rev.C82, 055202 (2010), http://arxiv.org/abs/1006.247
Phase diagrams in nonlocal PNJL models constrained by Lattice QCD results
Based on lattice QCD-adjusted SU(2) nonlocal Polyakov--Nambu--Jona-Lasinio
(PNJL) models, we investigate how the location of the critical endpoint in the
QCD phase diagram depends on the strenght of the vector meson coupling, as well
as the Polyakov-loop (PL) potential and the form factors of the covariant
model. The latter are constrained by lattice QCD data for the quark propagator.
The strength of the vector coupling is adjusted such as to reproduce the slope
of the pseudocritical temperature for the chiral phase transition at low
chemical potential extracted recently from lattice QCD simulations. Our study
supports the existence of a critical endpoint in the QCD phase diagram albeit
the constraint for the vector coupling shifts its location to lower
temperatures and higher baryochemical potentials than in the case without it.Comment: 23 pages, 10 figures. Version accepted in Phys. Part. Nucl. Lett. (to
appear), references adde
Chiral Modulations in Curved Space II: Conifold Geometries
In this paper, we extend our previous analysis concerning the formation of
inhomogeneous condensates in strongly-coupled fermion effective field theories
on curved spaces and include the case of conifold geometries that represent the
simplest tractable case of manifolds with curvature singularities. In the
set-up considered here, by keeping the genuine thermodynamical temperature
constant, we may single out the role that curvature effects play on the
breaking/restoration of chiral symmetry and on the appearance of inhomogeneous
phases. The first goal of this paper is to construct a general expression of
the finite temperature effective action for inhomogeneous condensates in the
case of four-fermion effective field theories on conifold geometries with
generic Riemannian smooth base (generalised cones). The other goal is to
implement numerically the above formal results and construct self-consistent
solutions for the condensate. We explicitly show that the condensate assumes a
kink-like profile, vanishing at the singularity that is surrounded by a bubble
of restored chiral symmetry phase.Comment: 14 pages; 4 figure
Quantum liquids resulting from quark systems with four-quark interaction
Quark ensembles influenced by strong stochastic vacuum gluon fields are investigated within the four-fermion interaction approximation. The comparative analysis of several quantum liquid models is performed and this analysis leads to the conclusion that the presence of a gas–liquid phase transition is their characteristic feature. The problem of the instability of small quark number droplets is discussed and it is argued that it is rooted in the chiral soliton formation. The existence of a mixed phase of the vacuum and baryon matter is proposed as a possible explanation of the latter stability
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