Search results for "Statistical physics"

Multiscaling Properties of Large-Scale Structure in the Universe

1995

The large-scale distribution of galaxies and galaxy clusters in the universe can be described in the mathematical language of multifractal sets. A particularly significant aspect of this description is that it furnishes a natural explanation for the observed differences in clustering properties of objects of different density in terms of multiscaling, the generic consequence of the application of a local density threshold to a multifractal set. The multiscaling hypothesis suggests ways of improving upon the traditional statistical measures of clustering pattern (correlation functions) and exploring further the connection between clustering pattern and dynamics.

Statistical analysis about diffusion of exercise addiction in Sicily

2020

Exercise Addiction (EA) is a behavioural dysfunction marked by uncontrolled compulsion towards all kinds of physical activity. With the purpose of understanding the epidemiology of this steadily increasing phenomenon, we have done a statistical analysis about some data obtained through the administration of an onlinequestionnaire (Google forms): the same one was also converted into paper-questionnaire and then it has been administered in many gyms in Palermo and Trapani (Sicily-Italy). The sample examined consists of 976 people aged between 14 and 65 (47.3% of them are women and 52.7% are men). For 53.8% of analysed people, physical activity is one of the most important things of their life…

Noise in physic$

2007

Scaling and mean-field-like behaviour in phase separation processes

1985

Extensive Monte Carlo calculations are used to study the still not well understood process of phase separation in binary systems. The results show that for a separation dominated by long-wavelength fluctuations a mean-field description holds in certain concentration regions. This, however, is only true for short times after the system has been brought into a non-equilibrium state. A crucial parameter is the interaction range. It determines the region and the time where the mean field description is valid. At later times the structure factor exhibits dynamical scaling. Scaling is also investigated for the metastable states. The results are applicable to polymer blends with long chains or bin…

KPZ equation with realistic short-range-correlated noise

2003

We study a realistic simulation model for the propagation of slow-combustion fronts in paper. In the simulations the deterministic part of the dynamics is that of the KPZ equation. The stochastic part, including in particular the short-range noise correlations, is taken from images of the structure of real paper samples. The parameters of the simulations are determined by using an inverse method applied to the experimental front data and by comparing the simulated and the experimental effective-noise distributions. Our model predicts well the shape of the spatial and temporal correlation functions, including the location of the crossovers from short-range (SR) to long-range (LR) behavior. T…

X-shaped space-time coherence in optical parametric generation

2007

We study the spatiotemporal coherence properties of superfluorescence radiation generated in optical parametric amplification of quantum noise. We show that the angular dispersion properties of the spatiotemporal spectra, measured in different phase-matching conditions, lead to a clear X-shaped structure of the mutual correlation function of the radiation. Within a statistical picture, we interpret the generated superfluorescence as a stochastic “gas” of quasistationary modes characterized by a skewed correlation in the spatiotemporal domain, with characteristics similar to linear and nonlinear X waves not describable within a separable approach in space and time.

Determination of the stochastic evolution equation from noisy experimental data

2003

We have determined the coefficients of the Kardar-Parisi-Zhang equation as functions of coarse graining, which best describe the time evolution and spatial behavior observed for slow-combustion fronts in sheets of paper and magnetic flux fronts in a thin-film high-Tc superconductor. Reconstruction of the relevant equation of motion and its coefficients was mainly based on the inverse method proposed by Lam and Sander [Phys. Rev. Lett. 71, 561 (1993)]. The coefficient of the nonlinear term was also determined from the local slope-dependence of the front velocity.

Does the Gogny interaction need a third Gaussian?

2016

International audience; By considering infinite matter constraints only, we suggest in this paper that the Gogny interaction should benefit from a third Gaussian in its central part. A statistical analysis is given to select the possible ranges which are compatible with these constraints and which minimize a $\chi^2$ function.

Monte Carlo simulation of alpha spectra in low-geometry measurements

1994

Abstract Monte Carlo simulation of alpha spectra obtained with semiconductor detectors in low-geometry has been developed. The proposed method reproduces adequately experimental spectra of alpha emitters by taking into account the energy losses and trajectory changes of alpha particles as consequences of their interactions in the source, backing and detector.

Searching for localized cosmic particle sources with an unbinned maximum likelihood approach

2006

Abstract An unbinned method to search for localized cosmic particle sources is presented. The expected source shape, the measured background shape, and the estimated angular resolution of individual tracks are used to construct a likelihood function. Estimates of the flux, the position and—in particular—the significance of a source can be readily obtained. A full confidence belt construction to deduce flux limits is presented. General statistical issues when searching for sources of unknown position are discussed.