887 research outputs found
Renormalization Group and Probability Theory
The renormalization group has played an important role in the physics of the
second half of the twentieth century both as a conceptual and a calculational
tool. In particular it provided the key ideas for the construction of a
qualitative and quantitative theory of the critical point in phase transitions
and started a new era in statistical mechanics. Probability theory lies at the
foundation of this branch of physics and the renormalization group has an
interesting probabilistic interpretation as it was recognized in the middle
seventies. This paper intends to provide a concise introduction to this aspect
of the theory of phase transitions which clarifies the deep statistical
significance of critical universality
Two Approaches to Imputation and Adjustment of Air Quality Data from a Composite Monitoring Network
An analysis of air quality data is provided for the municipal area of Taranto characterized by high environmental risks, due to the massive presence of industrial sites with elevated environmental impact activities. The present study is focused on particulate matter as measured by PM10 concentrations. Preliminary analysis involved addressing several data problems, mainly: (i) an imputation techniques were considered to cope with the large number of missing data, due to both different working periods for groups of monitoring stations and occasional malfunction of PM10 sensors; (ii) due to the use of different validation techniques for each of the three monitoring networks, a calibration procedure was devised to allow for data comparability. Missing data imputation and calibration were addressed by three alternative procedures sharing a leave-one-out type mechanism and based on {\it ad hoc} exploratory tools and on the recursive Bayesian estimation and prediction of spatial linear mixed effects models. The three procedures are introduced by motivating issues and compared in terms of performance
Binary mixtures of chiral gases
A possible solution of the well known paradox of chiral molecules is based on
the idea of spontaneous symmetry breaking. At low pressure the molecules are
delocalized between the two minima of a given molecular potential while at
higher pressure they become localized in one minimum due to the intermolecular
dipole-dipole interactions. Evidence for such a phase transition is provided by
measurements of the inversion spectrum of ammonia and deuterated ammonia at
different pressures. In particular, at pressure greater than a critical value
no inversion line is observed. These data are well accounted for by a model
previously developed and recently extended to mixtures. In the present paper,
we discuss the variation of the critical pressure in binary mixtures as a
function of the fractions of the constituents.Comment: 5 pages, 1 figure, text substantially based on arXiv:1501.02099 to be
presented in Progress in Electromagnetics Research Symposium (PIERS) 201
Two Approaches to Imputation and Adjustment of Air Quality Data from a Composite Monitoring Network
An analysis of air quality data is provided for the municipal area of Taranto characterized by high environmental risks, due to the massive presence of industrial sites with elevated environmental impact activities. The present study is focused on particulate matter as measured by PM10 concentrations. Preliminary analysis involved addressing several data problems, mainly: (i) an imputation techniques were considered to cope with the large number of missing data, due to both different working periods for groups of monitoring stations and occasional malfunction of PM10 sensors; (ii) due to the use of different validation techniques for each of the three monitoring networks, a calibration procedure was devised to allow for data comparability. Missing data imputation and calibration were addressed by three alternative procedures sharing a leave-one-out type mechanism and based on {\it ad hoc} exploratory tools and on the recursive Bayesian estimation and prediction of spatial linear mixed effects models. The three procedures are introduced by motivating issues and compared in terms of performance
An equilibrium state with macroscopic correlations
In this paper we show that the equilibrium macroscopic entropy of a generic
non reversible Kawasaki+Glauber dynamics is a non local functional of the
density. This implies that equilibrium correlations extend to macroscopic
distances.Comment: 8 page
Spontaneous symmetry breaking and inversion-line spectroscopy in gas mixtures
According to quantum mechanics chiral molecules, that is molecules that
rotate the polarization of light, should not exist. The simplest molecules
which can be chiral have four or more atoms with two arrangements of minimal
potential energy that are equivalent up to a parity operation. Chiral molecules
correspond to states localized in one potential energy minimum and can not be
stationary states of the Schr\"odinger equation. A possible solution of the
paradox can be founded on the idea of spontaneous symmetry breaking. This idea
was behind work we did previously involving a localization phase transition: at
low pressure the molecules are delocalized between the two minima of the
potential energy while at higher pressure they become localized in one minimum
due to the intermolecular dipole-dipole interactions. Evidence for such a
transition is provided by measurements of the inversion spectrum of ammonia and
deuterated ammonia at different pressures. A previously proposed model gives a
satisfactory account of the empirical results without free parameters. In this
paper, we extend this model to gas mixtures. We find that also in these systems
a phase transition takes place at a critical pressure which depends on the
composition of the mixture. Moreover, we derive formulas giving the dependence
of the inversion frequencies on the pressure. These predictions are susceptible
to experimental test.Comment: 15 pages, 11 figure
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