Primordial density perturbations with running spectral index: impact on non-linear cosmic structures

(abridged) We explore the statistical properties of non-linear cosmic structures in a flat $\Lambda$CDM cosmology in which the index of the primordial power spectrum for scalar perturbations is allowed to depend on the scale. Within the inflationary paradigm, the running of the scalar spectral index can be related to the properties of the inflaton potential, and it is hence of critical importance to test it with all kinds of observations, which cover the linear and non-linear regime of gravitational instability. We focus on the amount of running $\alpha_{\mathrm{S},0}$ allowed by an updated combination of CMB anisotropy data and the 2dF Galaxy Redshift Survey. Our analysis constrains $\alpha_{\mathrm{S},0} = -0.051^{+0.047}_{-0.053}$ $(-0.034^{+0.039}_{-0.040})$ at 95% Confidence Level when (not) taking into account primordial gravitational waves in a ratio as predicted by canonical single field inflation, in agreement with other works. For the cosmological models best fitting the data both with and without running we studied the abundance of galaxy clusters and of rare objects, the halo bias, the concentration of dark matter halos, the Baryon Acoustic Oscillation, the power spectrum of cosmic shear, and the Integrated Sachs-Wolfe effect. We find that counting galaxy clusters in future X-ray and Sunyaev-Zel'dovich surveys could discriminate between the two models, more so if broad redshift information about the cluster samples will be available. Likewise, measurements of the power spectrum of cosmological weak lensing as performed by planned all-sky optical surveys such as EUCLID could detect a running of the primordial spectral index, provided the uncertainties about the source redshift distribution and the underlying matter power spectrum are well under control.Comment: 17 pages, 14 figures, 4 tables. Accepted for publication on MNRA

A technique for evaluating the application of the pin-level stuck-at fault model to VLSI circuits

Accurate fault models are required to conduct the experiments defined in validation methodologies for highly reliable fault-tolerant computers (e.g., computers with a probability of failure of 10 to the -9 for a 10-hour mission). Described is a technique by which a researcher can evaluate the capability of the pin-level stuck-at fault model to simulate true error behavior symptoms in very large scale integrated (VLSI) digital circuits. The technique is based on a statistical comparison of the error behavior resulting from faults applied at the pin-level of and internal to a VLSI circuit. As an example of an application of the technique, the error behavior of a microprocessor simulation subjected to internal stuck-at faults is compared with the error behavior which results from pin-level stuck-at faults. The error behavior is characterized by the time between errors and the duration of errors. Based on this example data, the pin-level stuck-at fault model is found to deliver less than ideal performance. However, with respect to the class of faults which cause a system crash, the pin-level, stuck-at fault model is found to provide a good modeling capability

Statistical analysis of direct-strike lightning data (1980 to 1982)

Electromagnetic measurements are being made during direct lightning strikes by NASA Langley Center using a specially instrumented F-106B aircraft. The research is to aid refinement, characterization, and understanding of the lightning-aircraft interaction process and the lightning hazards to aircraft. Statistical methods are applied to characterize some aspects of the lightning data obtained from 176 strikes to the aircraft. Specific attention is given to the problem of estimating the upper extreme quantiles of the distributions of peak-to-peak values for currents and rates of change in the magnetic and flux densities. A formal treatment via a general location-scale family of models allows the estimation method to be adapted to the realized shapes the distributions. The shapes are examined by probability plotting methods

Metric perturbations at reheating: the use of spherical symmetry

We consider decay of the inflaton with a quartic potential coupled to other fields, including gravity, but restricted to spherical symmetry. We describe analytically an early, quasilinear regime, during which inflaton fluctuations and the metric functions are driven by nonlinear effects of the decay products. We present a detailed study of the leading nonlinear effects in this regime. Results of the quasilinear approximation, in its domain of applicability, are found to be consistent with those of fully nonlinear lattice studies. We discuss how these results may be promoted to the full three dimensions.Comment: 18 pages, revtex, 2 figure

Resonance enhancement of particle production during reheating

We found a consistent equation of reheating after inflation, which shows that for small quantum fluctuations the frequencies of resonance are slighted different from the standard ones. Quantum interference is taken into account and we found that at large fluctuations the process mimics very well the usual parametric resonance but proceed in a different dynamical way. The analysis is made in a toy quantum mechanical model and we discuss further its extension to quantum field theory.Comment: 4 pages, 4 figures(eps), using RevTe

Memory effect in melting behaviour, crystallization kinetics and morphology of poly(propylene terephthalate)

Crystallization kinetics and melting behaviour of poly(propylene terephthalate) (PPT) were investigated by means of differential scanning calorimetry and hot-stage optical microscopy. Isothermal crystallization kinetics was analysed according to the Avrami treatment. The effects of temperature and duration of melting on the overall rate of isothermal crystallization were studied: the rate was found to decrease with increasing melting temperature and melting time. This result was discussed on the basis of the gradual destruction of predetermined athermal nuclei. Values of the Avrami exponent close to 3 were obtained, regardless of the adopted thermal treatment and the crystallization temperature, Tc, in agreement with a crystallization process originating from predetermined nuclei and characterized by three-dimensional spherulitic growth. As a matter of fact, spacefilling spherulites were observed by optical microscopy at all Tc's, independent of the applied thermal treatments. For each of them, the rate of crystallization became lower as Tc increased, as usual at low undercooling where the crystallization process is controlled by nucleation. The observed multiple endotherms, which are commonly displayed by polyesters, were influenced by Tc and ascribed to melting and recrystallization processes. Linear and non-linear treatments were applied in order to estimate the equilibrium melting temperature for PPT, by using the corrected melting temperatures. The non-linear estimation yielded an about 33°C higher value with respect to the one obtained by means of the linear approach. Through the analysis of secondary nucleation theory, the classical II→III transition was found to occur at a temperature of 194°C. The average work of chain folding for nucleation was determined to be c. 5.2 kcal/mol. The heat of fusion was correlated to the specific heat increment for samples with different degree of crystallinity and the results were interpreted on the basis of the existence of an interphase, whose amount was found to depend on the thermal treatment the polymer was subjected to