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The FAMU experiment aims to measure for the first time the hyperfine splitting of the muonic hydrogen ground state. From this measurement the proton Zemach radius can be derived and this will shed light on the determination of the proton charge radius. In this paper, we describe the scientific goal, the method and the detailed preparatory work. This includes the outcome of preliminary measurements, subsequent refined simulations and the evaluation of the expected results. The experimental setup being built for the measurement of the hyperfine splitting to be performed at the RAL laboratory muon facility is also described.

We review a Dynamap European Life project whose main scope was the design, commissioning, and actual implementation of “real-time” acoustic maps in a district of the city of Milan (District 9, or Z9, composed of about 2000 road stretches), by employing a small number of noise monitoring stations within the urban zone. Dynamap is based on the idea of finding suitable sets of roads displaying similar daily traffic noise behavior, so that one can group them together into single dynamical noise maps. The Dynamap sensor network has been built upon twenty-four monitoring stations, which have been permanently installed in appropriate locations within the pilot zone Z9, by associating four sensors to each one of the six group of roads considered. In order to decide which road stretches belong to a group, a non-acoustic parameter is used, which is obtained from a traffic flow model of the city, developed and tested over the years by the “Enviroment, Mobility and Territory Agency” of Milan (EMTA). The fundamental predictive equation of Dynamap, for the local equivalent noise level at a given site, can be built by using real-time data provided by the monitoring sensors. In addition, the corresponding contributions of six static traffic noise maps, associated with the six group of roads, are required. The static noise maps can be calculated from the Cadna noise model, based on EMTA road traffic data referred to the ‘rush-hour’ (8:00–9:00 a.m.), when the road traffic flow is maximum and the model most accurate. A further analysis of road traffic noise measurements, performed over the whole city of Milan, has provided a more accurate description of road traffic noise behavior by using a clustering approach. It is found that essentially just two mean cluster hourly noise profiles are sufficient to represent the noise profile at any site location within the zone. In order words, one can use the 24 monitoring stations data to estimate the local noise variations at a single site in real time. The different steps in the construction of the network are described in detail, and several validation tests are presented in support of the Dynamap performance, leading to an overall error of about 3 dB. The present work ends with a discussion of how to improve the design of the network further, based on the calculation of the cross-correlations between monitoring stations’ noise data.

Recently, Takamoto et al. (2020) have discussed high precision measurements of gravity induced time dilation effects on optical lattice clocks located near the Earth surface. A relative tick frequency change, $\ensuremath{\delta}\ensuremath{\nu}/{\ensuremath{\nu}}_{0}=(49\text{ }337.8\ifmmode\pm\else\textpm\fi{}4.3){10}^{\ensuremath{-}18}$, is found between two optical lattice clocks, one located at the ground floor, $h=0\text{ }\text{ }\mathrm{m}$, and the second one at an altitude ${h}_{\mathrm{exp}}=452.596\text{ }\text{ }\mathrm{m}$, on the Skytree tower in Tokyo. The results are compared with the predictions of Einstein's equivalence principle (EEP) estimated as an average over gravimeter measurements at $h=0\text{ }\text{ }\mathrm{m}$ and $h=450\text{ }\text{ }\mathrm{m}$. We present a different derivation of the EEP prediction based on the calculation of the effective gravitational potential on the ground floor and at $h={h}_{\mathrm{exp}}$, in excellent agreement with the value $\ensuremath{\delta}\ensuremath{\nu}/{\ensuremath{\nu}}_{0}$, providing an independent method to validate the differences in time dilation measured experimentally. In addition, we obtain the next-order correction to the present results, which may be tested in future more accurate experiments.

The authors suggest a model to simulate the dynamics of ions in a supersonic plasma jet. The model relies on experimental argon ion, Ar(+), energy distribution functions measured by a quadrupole mass spectrometer at different positions along the central axis of a supersonic argon plasma jet. The latter is generated by the pressure difference between two vacuum chambers connected through a converging nozzle: a high-pressure chamber (P ≃ 3.20 Pa), where an inductively coupled argon plasma discharge is maintained, and a lower-pressure one (P ≃ 0.11 Pa), where the plasma jet expands. The model is based on the integration of the equations of motion of a single Ar(+), moving along the supersonic jet in a reference system in which neutral species are at rest. Ar(+)-Ar induced dipole interactions are treated using a 12-4 Lennard-Jones potential. The resulting collisions are considered to be purely elastic, and in addition to them, we allow for charge transfer processes. The energy and position of 1000 Ar(+) were calculated, using an integration time step of 10 ps for ion trajectories ranging from 5 mm to 20 mm from the nozzle, well inside the spatial extension of the supersonic jet. The numerically obtained ion energy distribution functions agree remarkably well with the experimental measurements. From our calculations we can draw conclusions about the energy loss and the mean free paths along the jet. In particular, we can distinguish between processes with and without charge transfer, allowing us to determine the effect of charge exchange phenomena in which the ion changes its nature. The calculated mean free paths were used to evaluate the effective cross sections for momentum transfer and charge transfer collisions, valid for ion energies in the range (0.5-10) eV, in very good agreement with those reported in the literature.

The effects of Coulomb interaction on charge transport in a model of light emission from an array of silicon nanoclusters are studied by Monte Carlo simulations. The array is sandwiched between a p-type and an n-type doped silicon crystals and electrons and holes are driven into the array by an applied electric field. Radiative recombinations of electrons and holes take place near the center of the array producing the emission of red light, and the total emission power is approximately proportional to the current injected into the system. It is found that the carrier-carrier interaction plays a crucial role in charge transport. Specifically, the self-interaction of charges inside each nanocluster is found to be the dominant interaction term for the semiclassical Hamiltonian considered. In addition, it drastically limits the current in the device giving rise to a strong non-linear relation between current and density of free carriers in the doped silicon crystals.

We present an ab initio calculation of the line shape of the photoabsorption spectrum of Na8 and Na+9 clusters at zero temperature, including the polarization effect driven by the electron-plasmon coupling, together with the electron-phonon coupling. The electron-plasmon coupling is found to yield a significant lowering of the energy centroid of the plasmons, whereas the main effect the electron-phonon coupling has is to smooth the spectrum. © 2005 IOP Publishing Ltd.

The effects of an edge biasing potential on the intermittent behaviour of the anomalous flux in a cold toroidal magnetoplasma is studied at different radial positions in the poloidal plane. It is found that both the fluctuations and cross-correlations between particle density and radial velocity vary as a function of the applied bias potential, leading to a strong reduction of the flux at the plasma core. The reduction is due to a large extent to the conspicuous decorrelation between density and velocity signals, while the corresponding fluctuations are much less sensitive to the applied field. The study of intermittent bursts indicates that a strong increase in their mean waiting times takes place at the core.

We present the most complete set of calculations to date of the ground state electronic properties and of the optical/UV response function of linear carbon chains CN, using ab-initio methods based on local density and on time-dependent local density approximations (LDA and TDLDA). Making use of the associated transition densities and wavefunctions we are able to provide microscopic insight into the collectivity of the corresponding plasmon spectrum in terms of correlated particle-hole excitations. From this analysis it is found that the (one-dimensional 1-D) delocalization of π (valence) electrons is responsible for the conspicuous values of the static dipole polarizability and of the high value of the exponent describing its dependence with the number of carbon atoms. Within this framework the electronic structure and linear response function of a carbon ring is also calculated. Although many properties of this function are similar to that associated with linear chains of the same number of atoms, the corresponding polarizabilities differ appreciably, providing a reliable method to distinguish between linear and close structures. The first principle results of the properties of linear carbon chains are compared with both theoretical and experimental results available in the literature, and constitute the basis for a systematic study of these 1-D s p-bonded systems, which have been found to be involved in such seemingly disparate phenomena as fullerene growth mechanism and diffuse interstellar bands. © 2002 Elsevier Science B.V. All rights reserved.

The electromagnetic response and photoemission spectrum of a linear carbon chain are obtained from ab initio calculations of its electronic structure and vibrational modes. Theoretical results are presented for a chain of 5 atoms for which the photoabsorption and photoemission spectra have been measured experimentally. The theory accurately accounts for the experimental observations.

We have studied long-time daily temperature records (between 56 and 218 years) obtained from 12 meteorological stations in Europe and North America from various climatological zones. To analyse the fluctuations of the daily temperatures around their average values, we have calculated directly the autocorrelation function C(ℓ) between two days separated by ℓ days, and applied also random-walk fluctuation analysis and wavelets methods, which can systematically overcome non-stationarities in the data. In addition, we have also analysed the distribution of the daily temperature fluctuations, which in most cases is well approximated by a Gaussian. Our analysis suggests that the persistence, characterized by the autocorrelation function C(ℓ), is long ranged and approximately decays with a power law C(ℓ) ≃ ℓ-γ, with roughly the same exponent γ ≈ 2/3 for all stations considered. This universal persistence law seems to be valid at least for one decade of years, but we cannot exclude the possibility that the range of the power-law correlations even exceeds the range of the temperature series considered. © 1998 Taylor and Francis Group, LLC.

Mean field theory and linear response methods as used in the description of nuclei and clusters are reviewed. These methods are applied to the electromagnetic response of C60. © 1994 Springer-Verlag.

We discuss vibrational properties and random walks on random fractal structures, in particular on the infinite percolation cluster at criticality. We show that the probabilities Pi, (r, t) of finding a random walker after t time steps on a site i at distance r from its starting point are characterized by a logarithmically broad distribution and display multifractal features. The corresponding vibrational amplitudes ψi(r,w), for fixed r and w, show similar features. In both cases, the multifractality vanishes on deterministic fractals and on those random fractals for which the fractal dimension dx in chemical space is equal to the fractal dimension df of the structure. By relating the distribution function which represents the average over all Pi(r, t), to the averaged envelope function ψi(r, w) describing the decay of vibrational excitations, we find that the vibrational excitations (fractons) are localized with a frequency-dependent localization length λ(w); the envelope function ψ(r, w) decays exponentially for r/λ> 1. Finally we discuss the vibrational density N(w) of states for quite general random AB networks consisting of A and B bonds with force constants fAand fB, 0

Highly magnetized pure electron plasmas confined in Penning-Malmberg traps allow to perform accurate experiments on effective two-dimensional (2D) fluid dynamics under well-controlled experimental conditions. Detailed experimental investigations of free decaying turbulence in a pure electron plasma using multi-resolution analysis (MRA) are presented. Coherent structures are extracted from the flow using a wavelet-based recursive denoising algorithm with an adaptative self-consistent threshold. The scaling behaviors of measured enstrophy and energy distributions are obtained and compared with recent experiments and theoretical predictions for 2D turbulence. Copyright © 2009 EPLA.

We perform Monte Carlo simulations for diffusion of charged particles in structurally disorderd lattices. As a consequence of the Coulomb interaction, pronounced backward correlations occur which lead to power-law behavior of the relevant transport quantities at intermediate time and frequency scales. Both the exponents and the size of the dispersive regime depend on temperature. Our simulations suggest that the combined effect of disorder and Coulomb interaction provides a new mechanism for understanding non-Debye relaxation, which is experimentally known for a wide class of materials. © 1991 The American Physical Society.

An array of silicon nanoclusters aimed at producing light emission upon injection of electrons and holes from external sources is studied by Monte Carlo simulations. The conditions for obtaining a significant charge accumulation in the emitting nanoclusters are investigated as a function of array geometry and applied electric fields. It is found that if a stationary state, reached for an applied field F-0, is suddenly perturbed by a field F-1 F-0, a significant increase in electron-hole pairs population can be obtained with respect to the case of a single field of constant intensity F-1, leading to enhanced light emission when the conductivity of the array is above 6 x 10(-10) [Omega cm](-1). The excess population thus created gets fully recombined on the time scale of milliseconds, suggesting a device that can produce enhanced light emission in the range of kilohertz.

A statistical analysis of density fluctuations in a cylindrical non-fusion device is performed. The experimental set-up is implemented in order to reach a turbulent behavior of the linear plasma column. Two different turbulent regimes are obtained corresponding to two selected sets of values for the discharge parameters. The first regime displays a rotating column characterized by the presence of a shear layer separating the plasma bulk from the tenuous plasma in the shadow of the limiter, the latter showing a strong intermittent behavior and superdiffusion. The second regime corresponds to a weakly-rotating column in which coherence is lost in the plasma bulk and a standard diffusive process takes place in the shadow region. These findings are supported by the calculation of the Hurst¿s exponent using Wavelet-analysis techniques. Furthermore the intermittent behavior is characterized and related to the diffusive process. Finally the shape of the probability distribution function (PDF) of density fluctuations seems to be well described by an analytical form suggested on the basis of a generalized statistics.

A constrained dynamics method suitable for molecular dynamics simulations is considered to study the long-time dynamics of polymer chains. The method is initially discussed on the basis of the Lagrangian and Hamiltonian formalisms for isolated polymer chains with fixed monomer - monomer links. Subsequently, the corresponding equations of motion are obtained for describing the dynamics of such polymer chains in the presence of a thermostat. The approach is applied to a few typical cases to illustrate how the formalism is implemented numerically and to elucidate its convergence properties when studying such systems in equilibrium. As an example, we consider the problem of reconstructing the backbone structure ( chain of C-alpha atoms) of protein Rubredoxin from its contact matrix. It is shown that the target structure is succesfully reached after a long transient regime ( typically in the range from 10(6) to 10(8) integration steps). A particular attractive extension of the algorithm presented here is to environment-dependent couplings, which could allow the study of the long-time polymer dynamics in realistic environments. The present method is thus expected to have useful applications in the modelling of the complex dynamics of bio-polymers such as proteins, and also in the context of nanoscale polymer materials

This chapter introduces two major classes of numerical methods used to study self-avoiding walks (SAWs) on deterministic and random fractals, namely, Monte Carlo (MC) methods and the exact enumeration (EE) technique. The advantages and disadvantages of both approaches are highlighted in connection to the different substrates and the statistical quantities of interest. Self-avoiding walks (SAWs) constitute the simplest, yet non-trivial model for studying the static behavior of a linear polymer embedded in a good solvent. Many MC methods have been developed for studying SAWs on regular lattices. These diverse algorithms can be classified according to static, quasistatic, and dynamic MC methods. The exact enumeration (EE) technique allows enumeration and evaluation of all SAW configurations on a given substrate. The chapter also discusses SAWs on three different substrates and compares them with the results obtained for SAWs on regular lattices. The first two substrates, Sierpinski triangular and square lattices, are representative members of the class of deterministic fractals, whereas percolation is the standard model for random fractals. Deterministic fractals consist of two distinct subgroups: the finitely (Sierpinski triangular) and infinitely (Sierpinski square) ramified fractals. The behavior of SAWs is drastically affected by the underlying substrate but certain similarities emerge: SAWs on Sierpinski triangular and square lattices display a kind of intermediate behavior between SAWs on the corresponding regular lattices and on percolation. The spatial characteristics of SAWs on Sierpinski square lattices are closer to those observed for regular lattices, while SAWs on Sierpinski triangular lattices are more similar to their counterparts on percolation. Scaling forms known for SAWs on regular lattices seem to remain valid also on deterministic and random fractals, while the corresponding relations between the scaling exponents need to be modified in some cases. © 2005 Elsevier B.V. All rights reserved.

The effects of a biasing potential on the statistical properties of the fluctuating flux, particle density and radial velocity time series in the nonfusion magnetoplasma Thorello [C. Riccardi, D. Xuantong, M. Salierno, L. Gamberale, and M. Fontanesi, Phys. Plasmas 4, 3749 (1997)] are studied. The shape evolution of the probability distribution function (PDF) of the temporal coarse-grained fluctuating flux is investigated as a function of the radial position in the plasma equatorial plane, for different values of the bias potential applied to a limiter. A reduction of cross correlations between density and radial velocity, concomitant with an increase in the shearing rate of the radial electric field, is found near the center of the plane as a function of the bias potential. The partial density-velocity cross correlations, evaluated at different time scales, reach their asymptotic values for times of the order of those describing the change in shape of the fluctuating flux PDF. The magnitude of the shearing rate of the radial electric field, calculated at different radial positions in the plane, is consistent with the expected decorrelation mechanism of turbulent transport. (C) 2004 American Institute of Physics.