High Energy Neutrinos from Cosmic Ray Interactions in Clusters of Galaxies

The spatial clustering of galaxies in galaxy clusters implies that the background of infrared (IR) light in the intracluster medium (ICM) may exceed the universal background. Cosmic rays injected within the ICM propagate diffusively and at low enough energies are trapped there for cosmological times. The photopion production interactions of cosmic rays with the IR photons are responsible for the generation of neutrinos whose detection may shed some light on the origin and propagation of high energy cosmic rays in the universe. Here we discuss our calculations of the flux of neutrinos from single clusters as well as the contribution of photopion production in clusters of galaxies to the diffuse neutrino background.Comment: 10 pages, 10 figures, submitted to PR

The Small Scale Anisotropies, the Spectrum and the Sources of Ultra High Energy Cosmic Rays

We calculate the number density and luminosity of the sources of ultra high energy cosmic rays (UHECRs), using the information about the small scale anisotropies and the observed spectra. We find that the number of doublets and triplets observed by AGASA can be best reproduced for a source density of $\sim 10^{-5} Mpc^{-3}$, with large uncertainties. The spectrum of UHECRs implies an energy input of $\sim 6\times 10^{44} erg yr^{-1} Mpc^{-3}$ above $10^{19}$ eV and an injection spectrum $\propto E^{-2.6}$. A flatter injection spectrum, $E^{-2.4}$, can be adopted if the sources have luminosity evolution $\propto (1+z)^4$. The combination of these two pieces of information suggests that the single sources should on average have a cosmic ray luminosity above $10^{19}$ eV of $L_{source}\approx 2\times 10^{42} erg s^{-1}$, weakly dependent upon the injection spectrum. Unfortunately, with the limited statistics of events available at present, there are approximately one-two orders of magnitude uncertainty in the source density provided above. We make predictions on the expected performances of the Auger and EUSO experiments, with particular attention for the expected improvements in our understanding of the nature of the sources of UHECRs. We find that a critical experimental exposure $\Sigma_c$ exists, such that experiments with exposure larger than $\Sigma_c$ can detect at least one event from each source at energies above $10^{20}$ eV. This represents a unique opportunity to directly count and identify the sources of UHECRs.Comment: Submitted to Astropart. Phy

Cercant l'atenció a la diversitat mitjançant la diversificació metodològica. Model de Proposta per la Unitat Didàctica d'electricitat dins l'àmbit de "Tecnologia i Digitalització" a 2n d'ESO

En aquest treball es fa una anàlisi de l'ús del llibre digital com a únic mètode docent i s'exposen certes limitacions detectades a l'hora de fer front a la diversitat i la inclusió de tot l'alumnat dins l'aula. Alhora, es fa una proposta d'una programació didàctica per al tema d'electricitat a 2n d'ESO, que inclou diverses metodologies actives per tal de combinar-les sense prescindir del llibre, ja que els alumnes l'han comprat, i així poder apropar-nos a un Disseny Universal de l'Aprenentatge. Les metodologies plantejades parteixen d'un enfocament que pretén augmentar la motivació de l'alumnat i alhora donar resposta a les adaptacions que determinen els Plans Individualitzats de l'alumnat

Successions d'interpolació en certs espais de funcions

Consultable des del TDXTítol obtingut de la portada digitalitzadaVegeu dbbresum1de1.pd

Particle Acceleration in Supernova Remnants and the Production of Thermal and Nonthermal Radiation

If highly efficient, cosmic ray production can have a significant effect on the X-ray emission from SNRs as well as their dynamical evolution. Using hydrodynamical simulations including diffusive shock acceleration, we produce spectra for both the thermal and nonthermal forward shock emission. For a given ambient density and explosion energy, we find that the position of the forward shock at a given age is a strong function of the acceleration efficiency, providing a signature of cosmic-ray production. Using an approximate treatment for the ionization state of the plasma, we investigate the effects of slow vs. rapid heating of the postshock electrons on the ratio of thermal to nonthermal X-ray emission at the forward shock. We also investigate the effects of magnetic field strength on the observed spectrum for efficient cosmic-ray acceleration. The primary effect of a large field is a considerable flattening of the nonthermal spectrum in the soft X-ray band. Spectral index measurements from X-ray observations may thus be indicators of the postshock magnetic field strength. The predicted gamma-ray flux from inverse-Compton (IC) scattering and neutral pion decay is strongly affected by the ambient conditions and, for the particular parameters used in our examples, the IC emission at E ~ 1 TeV exceeds that from pion decay, although at both lower and higher energies this trend is reversed for cases of high ambient density. More importantly, high magnetic fields produce a steepening of the electron spectrum over a wide energy range which may make it more difficult to differentiate between IC and pion-decay emission solely by spectral shape.Comment: 30 pages, 12 figures, submitted to ApJ January 200