A Faraway Quasar in the Direction of the Highest Energy Auger Event

The highest energy cosmic ray event reported by the Auger Observatory has an energy of 148 EeV. It does not correlate with any nearby (z$<$0.024) object capable of originating such a high energy event. Intrigued by the fact that the highest energy event ever recorded (by the Fly's Eye collaboration) points to a faraway quasar with very high radio luminosity and large Faraday rotation measurement, we have searched for a similar source for the Auger event. We find that the Auger highest energy event points to a quasar with similar characteristics to the one correlated to the Fly's Eye event. We also find the same kind of correlation for one of the highest energy AGASA events. We conclude that so far these types of quasars are the best source candidates for both Auger and Fly's Eye highest energy events. We discuss a few exotic candidates that could reach us from gigaparsec distances.Comment: 13 pages (version to be published in JCAP

Consequences of short range interactions between dark matter and protons in galaxy clusters

Protons gain energy in short range collisions with heavier dark matter particles (DMPs) of comparable velocity dispersion. We examine the conditions under which the heating of baryons by scattering off DMPs can offset radiative cooling in the cores of galaxy clusters. Collisions with a constant cross section independent of the relative velocity of the colliding particles, cannot produce stable thermal balance. In this case, avoiding an unrealistic increase of the central temperatures yields the upper bound on the cross-section, \sigma_xp<10^-25 cm^2 (m_x/m_p), where m_x and m_p are the DMP and proton mass, respectively. A stable balance, however, can be achieved for a power law dependence on the relative velocity, V, of the form \sigma_xp \propto V^a with a<-3. An advantage of this heating mechanism is that it preserves the metal gradients observed in clusters.Comment: 7 pages, new calculations include

Closing the Window on Strongly Interacting Dark Matter with IceCube

We use the recent results on dark matter searches of the 22-string IceCube detector to probe the remaining allowed window for strongly interacting dark matter in the mass range 10^4<m_X<10^15 GeV. We calculate the expected signal in the 22-string IceCube detector from the annihilation ofsuch particles captured in the Sun and compare it to the detected background. As a result, the remaining allowed region in the mass versus cross sectionparameter space is ruled out. We also show the expected sensitivity of the complete IceCube detector with 86 strings.Comment: 5 pages, 7 figures. Uppdated figures 2 and 3 (y-axis normalization and label) . Version accepted for publication in PR

Heisenberg model in a random field: phase diagram and tricritical behavior

By using the differential operator technique and the effective field theory scheme we study the tricritical behavior of Heisenberg classical model of spin-1/2 in a random field. The phase diagram in the T-h plane on a square and simple cubic lattice for a cluster with two spins is obtained when the random field is bimodal distributed.Comment: 10 pages, 1 figur

Piper colubrinum Link. porta-enxêrto para Piper nigrum L. resistente às enfermidades causadas por Phytophthora palmivora Butl. e Fusarium solani f. piperi.

O sistema radicular da pimenta do reino (Piper nigrum L.) está sujeito ao ataque dos fungos do solo Fusarium solani f. piperi e Phytophthora palmivora (Butl.) Butl. Em testes de laboratório a espécie Piper colubrinum Link., compatível com a pimenta do reino, mostrou elevada resistência às enfermidades causadas pelos citados patógenos. Poderia ser utilizada como porta-enxêrto resistente em culturas extensas com fim lucrativo, desde que a produção venha a ser compensadora. A percentagem de pegamento dos enxêrtos feitos, foi elevada: acima de 98%. O desenvolvimento vegetativo das pimenteiras enxertadas, em áreas experimentais, no campo, vem sendo considerado bom. São relatados os processos de preparo dos porta-enxertos, métodos de enxertia e plantio no campo definitivo. A pimenteira enxertada só se desenvolve bem em áreas onde o solo possui umidade disponível constante.Separata da Pesquisa Agropecuária Brasileira, série agronomia, v. 3, p. 141-145, 1968