Social Struggles as Epistemic Struggles

__Abstract__ This contribution offers a view on social struggles as epistemic struggles to critically engage with the Activism 2010+ debate. Our core idea is that socia

The rate of cosmic ray showers at large zenith angles: a step towards the detection of ultra-high energy neutrinos by the Pierre Auger Observatory

It is anticipated that the Pierre Auger Observatory can be used to detect cosmic neutrinos of >10^19 eV that arrive at very large zenith angles. However showers created by neutrino interactions close to the detector must be picked out against a background of similar events initiated by cosmic ray nuclei. As a step towards understanding this background, we have made the first detailed analysis of air showers recorded at Haverah Park (an array which used similar detectors to those planned for the Auger Observatory) with zenith angles above 60 degs. We find that the differential shower rate from 60 degs to 80 degs. can be predicted accurately when we adopt the known primary energy spectrum above 10^17 eV and assume the QGSJET model and proton primaries. Details of the calculation are given.Comment: 22 pages, 12 figures, to appear in Astroparticle Physic

A comprehensive study of shower to shower fluctuations

By means of Monte Carlo simulations of extensive air showers (EAS), we have performed a comprehensive study of the shower to shower fluctuations affecting the longitudinal and lateral development of EAS. We split the fluctuations into physical fluctuations and those induced by the thinning procedure customarily applied to simulate showers at EeV energies and above. We study the influence of thinning on the calculation of the shower to shower fluctuations in the simulations. For thinning levels larger than 10^(-5) - 10^(-6), the determination of the shower to shower fluctuations is hampered by the artificial fluctuations induced by the thinning procedure. However, we show that shower to shower fluctuations can still be approximately estimated, and we provide expressions to calculate them. The influence of fluctuations of the depth of first interaction on the determination of shower to shower fluctuations is also addressed.Comment: 17 pages, 15 figure

Are High Energy Cosmic Rays Magnetic Monopoles?

We argue that magnetic monopoles can not be associated to the highest energy cosmic rays as recently suggested. Both the observed spectrum and the arrival direction disagree with observation.Comment: 15 pages, 6 ps fig. included, Late

An Analytical Approach to Fluctuations in Showers

We review the problem of fluctuations in particle shower theory. By using a generalization of Furry equation, we find relations between the $n$--particle correlation function and the number of particles average or 1--particle correlation function. Such relations show that the average is the only independent dynamical variable. We also develop a numerical code to solve the equation for the correlation functions and compare the results with those from a Montecarlo simulation which show a perfect agreement between both methods.Comment: 18 pages Latex file and 3 PS figures. Uses Revtex and epsfig.sty Accepted for publication in Astroparticle Physic

Spin in the Worldline Path Integral in 2+1 Dimensions

We construct a worldline path integral for the effective action and propagator of a Dirac field in 2+1 dimensions in an Abelian gauge field background. Integrating over an auxiliary gauge group variable we derive a worldline action depending only on $x(\tau)$, the spacetime paths. We show that that action is a combination of a kinetic term plus a spin action. The first is proportional to $\delta[\dot{x}^2(\tau)- 1]$. The second agrees exactly with the spin action one should expect for a spin-1/2 field.Comment: 23 pages, no figures. Version extended with some applications and a more detailed explanation of the classical limi

Kinetic study of Cu2S–FeS mixtures in an oxidative environment by thermogravimetric and thermodynamic analysis

Two samples of Cu2S–FeS mixtures were prepared in order to study the thermal oxidation evolution of the raw materials used during the first and second sub-stages of slag blowing in a converter furnace. To determine the thermal evolution in an oxidative environment, thermogravimetric analysis (TGA) was performed on both samples at four linear heating ramps (5, 10, 15 and 20 ◦C min 1), obtaining similar curves in both cases. Of the methods studied, Friedman, Coats-Redfern, Flynn-Wall-Ozawa and Kissinger-Akahira-Sunose, the latter was found to be the most suitable to represent the oxidative evolution of Cu2S–FeS mixtures. The kinetic parameters calculated using Kissinger-Akahira-Sunose method are highly dependent on the degree of conversion. The results obtained for the activation energy ranging between 10 and 20 Kj mol 1 for conversion rates of 0.2, and between 30 and 50 Kj mol 1 for conversion rates of 0.9. In addition, a thermodynamic computational model was developed to determine the reactions taking place during the oxidation of the Cu2S–FeS mixturesThis work was carried out with financial support from the Research and Transfer Policy Strategy of the University of Huelva (Call for Industrial Doctorate grants at the University of Huelva). The authors also wish to thank the GEA Institute of the Universidad de Concepci´ on, Chile, whose facilities were made available to us to carry out a significant part of the experimental work performedDepartamento de Ingeniería Química, Química Física y Ciencias de los Materiale

Class of correlated random networks with hidden variables

We study a class models of correlated random networks in which vertices are characterized by \textit{hidden variables} controlling the establishment of edges between pairs of vertices. We find analytical expressions for the main topological properties of these models as a function of the distribution of hidden variables and the probability of connecting vertices. The expressions obtained are checked by means of numerical simulations in a particular example. The general model is extended to describe a practical algorithm to generate random networks with an \textit{a priori} specified correlation structure. We also present an extension of the class, to map non-equilibrium growing networks to networks with hidden variables that represent the time at which each vertex was introduced in the system

Mean-field analysis of the q-voter model on networks

We present a detailed investigation of the behavior of the nonlinear q-voter model for opinion dynamics. At the mean-field level we derive analytically, for any value of the number q of agents involved in the elementary update, the phase diagram, the exit probability and the consensus time at the transition point. The mean-field formalism is extended to the case that the interaction pattern is given by generic heterogeneous networks. We finally discuss the case of random regular networks and compare analytical results with simulations.Comment: 20 pages, 10 figure

Collective behavior in nuclear interactions and shower development

The mechanism of hadronic interactions at very high energies is still unclear. Available accelerator data constrain weakly the forward rapidity region which determines the development of atmospheric showers. This ignorance is one of the main sources of uncertainty in the determination of the energy and composition of the primary in hadron-induced atmospheric showers. In this paper we examine the effect on the shower development of two kinds of collective effects in high-energy hadronic interactions which modify the production of secondary particles. The first mechanism, modeled as string fusion, affects strongly the central rapidity region but only slightly the forward region and is shown to have very little effect on the shower development. The second mechanism implies a very strong stopping; it affects modestly the profile of shower maximum but broadens considerably the number distribution of muons at ground. For the latter mechanism, the development of air showers is faster mimicking a heavier projectile. On the other hand, the number of muons at ground is lowered, resembling a shower generated by a lighter primary.Comment: 17 pages, 10 figure