Long-range epidemic spreading in a random environment

Modeling long-range epidemic spreading in a random environment, we consider a quenched disordered, $d$-dimensional contact process with infection rates decaying with the distance as $1/r^{d+\sigma}$. We study the dynamical behavior of the model at and below the epidemic threshold by a variant of the strong-disorder renormalization group method and by Monte Carlo simulations in one and two spatial dimensions. Starting from a single infected site, the average survival probability is found to decay as $P(t) \sim t^{-d/z}$ up to multiplicative logarithmic corrections. Below the epidemic threshold, a Griffiths phase emerges, where the dynamical exponent $z$ varies continuously with the control parameter and tends to $z_c=d+\sigma$ as the threshold is approached. At the threshold, the spatial extension of the infected cluster (in surviving trials) is found to grow as $R(t) \sim t^{1/z_c}$ with a multiplicative logarithmic correction, and the average number of infected sites in surviving trials is found to increase as $N_s(t) \sim (\ln t)^{\chi}$ with $\chi=2$ in one dimension.Comment: 12 pages, 6 figure

Cross sections of proton-induced reactions on 152Gd, 155Gd and 159Tb with emphasis on the production of selected Tb radionuclides

Cross sections are presented for various Dy, Tb and Gd radionuclides produced in the proton bombardment of 159Tb as well as for the reactions 152Gd(p,4n)149Tb and 155Gd(p,4n)152Tb up to 66 MeV. The experimental excitation functions are compared with theoretical predictions by means of the geometrydependent hybrid (GDH) model as implemented in the code ALICE/ASH, as well as with values from the TENDL-2012 library and previous literature experimental data, where available. Physical yields have been derived for the production of some of the medically important radioterbiums, namely 149Tb (radionuclide therapy), 152Tb (PET) and 155Tb (SPECT). The indirect production of high-purity 155Tb via the decay of its precursor 155Dy is reported. The possibility of a large-scale production facility based on a commercial 70 MeV cyclotron is also discussed

Universality class of fiber bundles with strong heterogeneities

We study the effect of strong heterogeneities on the fracture of disordered materials using a fiber bundle model. The bundle is composed of two subsets of fibers, i.e. a fraction 0<\alpha<1 of fibers is unbreakable, while the remaining 1-\alpha fraction is characterized by a distribution of breaking thresholds. Assuming global load sharing, we show analytically that there exists a critical fraction of the components \alpha_c which separates two qualitatively different regimes of the system: below \alpha_c the burst size distribution is a power law with the usual exponent \tau=5/2, while above \alpha_c the exponent switches to a lower value \tau=9/4 and a cutoff function occurs with a diverging characteristic size. Analyzing the macroscopic response of the system we demonstrate that the transition is conditioned to disorder distributions where the constitutive curve has a single maximum and an inflexion point defining a novel universality class of breakdown phenomena

Lattice study of the Coleman--Weinberg mass in the SU(2)-Higgs model

Radiative symmetry breaking is a well known phenomenon in perturbation theory. We study the problem in a non-perturbative framework, i.e. lattice simulations. The example of the bosonic sector of the SU(2)-Higgs model is considered. We determine the minimal scalar mass which turns out to be higher than the mass value given by 1-loop continuum perturbation theory.Comment: Contribution to ICHEP-02, Amsterdam, 24-31 July 2002, 2 pages, 1 figur

Anderson transition and multifractals in the spectrum of the Dirac operator of Quantum Chromodynamics at high temperature

We investigate the Anderson transition found in the spectrum of the Dirac operator of Quantum Chromodynamics (QCD) at high temperature, studying the properties of the critical quark eigenfunctions. Applying multifractal finite-size scaling we determine the critical point and the critical exponent of the transition, finding agreement with previous results, and with available results for the unitary Anderson model. We estimate several multifractal exponents, finding also in this case agreement with a recent determination for the unitary Anderson model. Our results confirm the presence of a true Anderson localization-delocalization transition in the spectrum of the quark Dirac operator at high-temperature, and further support that it belongs to the 3D unitary Anderson model class.Comment: 10 pages, 6 figure

Anderson localization through Polyakov loops: lattice evidence and Random matrix model

We investigate low-lying fermion modes in SU(2) gauge theory at temperatures above the phase transition. Both staggered and overlap spectra reveal transitions from chaotic (random matrix) to integrable (Poissonian) behavior accompanied by an increasing localization of the eigenmodes. We show that the latter are trapped by local Polyakov loop fluctuations. Islands of such "wrong" Polyakov loops can therefore be viewed as defects leading to Anderson localization in gauge theories. We find strong similarities in the spatial profile of these localized staggered and overlap eigenmodes. We discuss possible interpretations of this finding and present a sparse random matrix model that reproduces these features.Comment: 11 pages, 23 plots in 11 figures; some comments and references added, some axis labels corrected; journal versio

Comparing the performance of stellar variability filters for the detection of planetary transits

We have developed a new method to improve the transit detection of Earth-sized planets in front of solar-like stars by fitting stellar microvariability by means of a spot model. A large Monte Carlo numerical experiment has been designed to test the performance of our approach in comparison with other variability filters and fitting techniques for stars of different magnitudes and planets of different radius and orbital period, as observed by the space missions CoRoT and Kepler. Here we report on the results of this experiment.Comment: 4 pages, 3 postscript figures, Transiting Planets Proceeding IAU Symposium No.253, 200