QCD spectra and random matrix models

We summarize some recent results on the application of macroscopic spectral properties of random matrix models (RMM) to the QCD spectra. A comparison to existing lattice simulation is presented both for staggered and Wilson fermions for high but finite temperature. We consider two types of mixing between the four lowest Matsubara modes, corresponding to third and fifth order algebraic equation for the pertinent resolvent, respectively.     

Theory of SEDM spectra in simple relaxation models

Theory of the SEDM spectra in the two-level relaxation model is revisited. It is shown that the very kind of relaxation behaviour depends on the pure static parameters-spectral width of incident beam and detector broadening, the refined version of the spectral shape being given. Also the distribution of SEDM spectral satellites for more complicated dynamical models is analyzed. The high sensitivity of SEDM spectra to the kinetic mechanism of relaxation is revealed.     

Compensation for receiver bandpass effects on ultrasonic backscatter power spectra using a random medium reference

A linear model of an ultrasonic pulse-echo system is used to express the measured power spectrum as the product of a scattering medium power spectrum and a transfer function accounting for system effects. Transfer functions are experimentally determined for multiple ranges using a random medium reference. Measured power spectra normalized by these functions are shown to be in close agreement with theoretical power spectra both in shape and absolute magnitude. The results indicate that the model allows scattering media to be distinguished when the media backscatter characteristics differ in the bandwidth of the measurement system.     

Large dimension forecasting models and random singular value spectra

We present a general method to detect and extract from a finite time sample statistically meaningful correlations between input and output variables of large dimensionality. Our central result is derived from the theory of free random matrices, and gives an explicit expression for the interval where singular values are expected in the absence of any true correlations between the variables under study. Our result can be seen as the natural generalization of the Marčenko-Pastur distribution for the case of rectangular correlation matrices. We illustrate the interest of our method on a set of macroeconomic time series.     

A simple statistical modeling of random phase reference in holographic memory

We present a simple modeling of random phase reference in holographic memory. The proposed model is analyzed by a statistical approach. Improvement on selectivity using random phase reference is shown in comparison with uniform phase plane wave reference and Gaussian beam reference. This simple and efficient model provides a physical insight and is verified by some experiments.     

Auditory profile analysis of irregular sound spectra

The discrimination of changes in the shapes of sound spectra is reported. The change was always an intensity increment to the 948-Hz component of a multitone complex. First, the ability of naive listeners to learn to discriminate a change in a "regular" background or reference spectrum (equal-level tones equally spaced in logarithmic frequency) was measured as a function of the number of trials. On the average, threshold improved about 10 dB over 3000 trials, with about 50% of the decrease in threshold occurring during the first 750 trials. In a subsequent series of experiments, the overall pattern of spectral shape of the background was varied randomly. Two kinds of perturbations in spectral shape were employed: Randomly choosing the frequencies of the reference spectra and randomly choosing the amplitudes of the components of the reference spectra. The experimental manipulations involved fixing the random spectra across a block of trials, varying the reference spectra from interval to interval of each trial, and providing extensive practice in discriminating specific randomly perturbed reference spectra. The results of the spectrum-learning and random perturbation experiments provide insight into the roles of critical band filtering, sensory variability, and short-term and long-term memory representations in auditory profile analysis. Further, the appropriateness of the generalization of a simple energy detection model is discussed.     

A simple approach to the analysis of positron lifetime spectra

A new method is proposed to deal with analysis of positron annihilation lifetime spectra which defy ordinary computer fitting. The method is particularly suited for investigations of defects in metals.     

Double passage analysis in random media using two-scale random propagators

Abstract

In location and remote sensing experiments there arise a number of effects related to the double passage of the backscattered field through the same random inhomogeneities as the incident one. To account for the correlation of the forward–backward propagating events, there is a need for a measure in which the random information along the propagation path is preserved. For the generation of even statistical moments, the relevant measure defined in the recently formulated stochastic geometrical theory of diflraction is the two-point random function (TPRF)—a paired field measure which is propagated along the geometrical rays of the deterministic background medium. From this function all even statistical moments can be generated. Here we present an approximate analytical solution for the high-frequency propagator obtained by applying the multiscale expansion asymptotic procedure to the partial differential equation governing the propagation a1 the TPRF. The test of the solution is performed on canonical backscattering problems based on point source–point scatterer and paint source–plane mirror configurations, which justifies its further application for construction of the coherence measures of the rctrareflected field. Coherence properties of the plane and spherical wavefields reflected backward by a plane mirror were investigated. Further, we investigated the intensity enhancement effects observed in the double passage of a Gaussian beam retroreflected from a plane mirror. Asymptotic expressions lor the retroreflected intensity are obtained, and their computations show good agreement with the direct numerical evaluations.     

Paramagnetic Mössbauer relaxation spectra by simple ab initio and stochastic models

The stochastic and ab initio (resolvent) methods for the calculation of Mössbauer relaxation spectra are shortly reviewed. The relaxation matrix based on a first order dynamical Hamiltonian is calculated and corresponding simulations are presented. The spin-phonon interaction spectral bath densities are calculated in the Debye approximation for the direct one and two phonon processes. Some least squares fits are presented.     

Double passage analysis in random media using two-scale random propagators

In location and remote sensing experiments there arise a number of effects related to the double passage of the backscattered field through the same random inhomogeneities as the incident one. To account for the correlation of the forward-backward propagating events, there is a need for a measure in which the random information along the propagation path is preserved. For the generation of even statistical moments, the relevant measure defined in the recently formulated stochastic geometrical theory of diflraction is the two-point random function (TPRF)—a paired field measure which is propagated along the geometrical rays of the deterministic background medium. From this function all even statistical moments can be generated. Here we present an approximate analytical solution for the high-frequency propagator obtained by applying the multiscale expansion asymptotic procedure to the partial differential equation governing the propagation a1 the TPRF. The test of the solution is performed on canonical backscattering problems based on point source-point scatterer and paint source-plane mirror configurations, which justifies its further application for construction of the coherence measures of the rctrareflected field. Coherence properties of the plane and spherical wavefields reflected backward by a plane mirror were investigated. Further, we investigated the intensity enhancement effects observed in the double passage of a Gaussian beam retroreflected from a plane mirror. Asymptotic expressions lor the retroreflected intensity are obtained, and their computations show good agreement with the direct numerical evaluations.     

Full profile analysis of the 29Si NMR spectra of LTL-framework zeolites

Full profile analyses of the digitized ²⁹Si NMR spectra of a potassium zeolite L and a gallosilicate analog are described. Both spectra can be fitted reasonably based on the assumption that they comprise only a single set of SinAl(Ga); n=0−4 peaks, reflecting that the mean T-O-T angles for the two T-sites (T=tetrahedral species, Si, Al or Ga) are similar.     

Central auditory processing of peripheral vowel spectra

This paper presents a review of recent experiments in vowel perception done at the Pavlov Institute of Physiology in Leningrad. The data concern three topics: experimental procedures appropriate for the study of phonetic quality perception, processing of the auditory spectral shape of a vowel, and processing of the auditory dynamic spectrum of a vowel.     

Curious properties of simple random walks

A simple random walker on the line of integers shows remarkable similarities to relativistic particles.     

Evaluation of plasmon-loss spectra of molybdenum using elastic-peak electron spectroscopy

Plasmon-loss spectra of clean polycrystalline molybdenum surfaces have been determined in the primary energy range E_p = 50–3000 eV. Spectra a distributions (nonderivative mode). A simplified model is described for evaluating plasmon-loss spectra using elastic-peak electron spectroscopy, as de of elastically reflected electrons is determined by integrating the N(E) spectrum of secondary and backscattered electrons. The ratio of the ar (23–24 eV) to that of the elastic peak is Pλ, the product of the probability for creating a volume plasmon loss and the inelastic mean free pat second plasmon-loss peak is (Pλ)². Evaluation of our experimental plasmon-loss spectra gives Pλ = 0.4–0.5 for E_p > 500 eV. Th constitutes ～50% of all losses determining the IMFP, interband loss processes being important in the remainder. For the low energy range, E_p found. For E_p < 100 eV, no volume plasmon-loss peak could be detected in our N(E) spectra. The simplified model proves to be valid fo plasmon-loss peak (11–12 eV), i.e., such that N_pls/N_e ? 10^?2. Some results are presented concerning surface plasmon losses as molybdenum surface.     

Study on random and coherence states using a family of CML models

A family of coupled map lattice (CML) models has been developed to simulate the interaction of convection, diffusion and dispersion in both weakly and strongly coupled cases. With variation of parameters, the models can simulate those systems of convection dominating, diffusion dominating, and dispersion dominating states. Not only coherent and turbulent properties as well as their interrelations, but also the transitional state between any modes with local coupling and global coupling are analysed to demonstrate the essential characteristics of any state. Numerical results show that the models are capable of simulating both layered coupling and stochastic mechanism, and thus can be conveniently used to analyse an initiative and driven coupled system. Results of numerical simulation also lead us to understand whether or not turbulence coherent structure is formed by modulation of wave packet. Finally, the duality of wave and particle characters of turbulence is illustrated in the numerical simulation.     

Evaluation of sun glint models using MODIS measurements

To understand the performance of various sun glint models, we have carried out comparison studies with measurements from Moderate Resolution Imaging Spectroradiometer (MODIS) for several popular sun glitter models, including the Cox-Munk models, Ebuchi-Kizu models, Breon-Henriot models, etc., over the open oceans using MODIS data at the near-infrared (NIR) (859 nm) and shortwave infrared (SWIR) bands (1240 and 2130 nm). Sun glint models with and without a wind direction dependence were evaluated. To obtain the MODIS-measured glint reflectance from the total reflectance at the top of the atmosphere, we performed atmospheric corrections to remove the effects of atmospheric absorption as well as radiance contributions from molecules (Rayleigh scattering) and aerosols. We have selected 12 MODIS sun glint scenes over various open ocean regions for this study. Our results indicate that overall, the Cox-Munk [1] model with the wind direction dependence has the best performance in terms of correlation coefficients with the MODIS measurements. The Breon-Henriot [8] model performed similarly as from the Cox-Munk model as two models are in fact very close. Findings from these evaluations can improve our ability to accurately remove the sun glint contamination in MODIS imagery and produce robust satellite ocean color and atmosphere products.     

Rapid classification of protein structure models using unassigned backbone RDCs and probability density profile analysis (PDPA)

A method of identifying the best structural model for a protein of unknown structure from a list of structural candidates using unassigned 15N1H residual dipolar coupling (RDC) data and probability density profile analysis (PDPA) is described. Ten candidate structures have been obtained for the structural genomics target protein PF2048.1 using ROBETTA. 15N1H residual dipolar couplings have been measured from NMR spectra of the protein in two alignment media and these data have been analyzed using PDPA to rank the models in terms of their ability to represent the actual structure. A number of advantages in using this method to characterize a protein structure become apparent. RDCs can easily and rapidly be acquired, and without the need for assignment, the cost and duration of data acquisition is greatly reduced. The approach is quite robust with respect to imprecise and missing data. In the case of PF2048.1, a 79 residue protein, only 58 and 55 of the total RDC data were observed. The method can accelerate structure determination at higher resolution using traditional NMR spectroscopy by providing a starting point for the addition of NOEs and other NMR structural data.