What brakes the Crab pulsar?

Optical observations provide convincing evidence that the optical phase of the Crab pulsar follows the radio one closely. Since optical data do not depend on dispersion measure variations, they provide a robust and independent confirmation of the radio timing solution. The aim of this paper is to find a global mathematical description of Crab pulsar's phase as a function of time for the complete set of published Jodrell Bank radio ephemerides (JBE) in the period 1988-2014. We apply the mathematical techniques developed for analyzing optical observations to the analysis of JBE. We break the whole period into a series of episodes and express the phase of the pulsar in each episode as the sum of two analytical functions. The first function is the best-fitting local braking index law, and the second function represents small residuals from this law with an amplitude of only a few turns, which rapidly relaxes to the local braking index law. From our analysis, we demonstrate that the power law index undergoes "instantaneous" changes at the time of observed jumps in rotational frequency (glitches). We find that the phase evolution of the Crab pulsar is dominated by a series of constant braking law episodes, with the braking index changing abruptly after each episode in the range of values between 2.1 and 2.6. Deviations from such a regular phase description behave as oscillations triggered by glitches and amount to fewer than 40 turns during the above period, in which the pulsar has made more than 2.0e10 turns. Our analysis does not favor the explanation that glitches are connected to phenomena occurring in the interior of the pulsar. On the contrary, timing irregularities and changes in slow down rate seem to point to electromagnetic interaction of the pulsar with the surrounding environment.Comment: 11 pages, 8 figures, 3 tables; accepted for publication in Astronomy & Astrophysic

Nori 1-motives

Let EHM be Nori's category of effective homological mixed motives. In this paper, we consider the thick abelian subcategory EHM_1 generated by the i-th relative homology of pairs of varieties for i = 0,1. We show that EHM_1 is naturally equivalent to the abelian category M_1 of Deligne 1-motives with torsion; this is our main theorem. Along the way, we obtain several interesting results. Firstly, we realize M_1 as the universal abelian category obtained, using Nori's formalism, from the Betti representation of an explicit diagram of curves. Secondly, we obtain a conceptual proof of a theorem of Vologodsky on realizations of 1-motives. Thirdly, we verify a conjecture of Deligne on extensions of 1-motives in the category of mixed realizations for those extensions that are effective in Nori's sense

Caracterização da variabilidade genética de populações locais de pimenta dedo-de-moça, utilizando marcadores RAPD.

bitstream/item/30461/1/boletim-80.pd

Divergência genética entre acessos do banco ativo de germoplasma de cebola da Embrapa Clima Temperado revelada por marcadores RAPD.

bitstream/item/30465/1/boletim-81.pd

Oscillations of solar and atmospheric neutrinos

Motivated by recent results from SuperKamiokande, we study both solar and atmospheric neutrino fluxes in the context of oscillations of the three known neutrinos. We aim at a global view which identifies the various possibilities, rather than attempting the most accurate determination of the parameters of each scenario. For solar neutrinos we emphasise the importance of performing a general analysis, independent of any particular solar model and we consider the possibility that any one of the techniques --- chlorine, gallium or water Cerenkov --- has a large unknown systematic error, so that its results should be discarded. The atmospheric neutrino anomaly is studied by paying special attention to the ratios of upward and downward going nu_e and nu_mu fluxes. Both anomalies can be described in a minimal scheme where the respective oscillation frequencies are widely separated or in non-minimal schemes with two comparable oscillation frequencies. We discuss explicit forms of neutrino mass matrices in which both atmospheric and solar neutrino fluxes are explained. In the minimal scheme we identify only two `zeroth order' textures that can result from unbroken symmetries. Finally we discuss experimental strategies for the determination of the various oscillation parameters.Comment: 20 pages, 7 figures. Final version: one reference added; fit of atmospheric neutrinos improve

Bipartite Bell inequalities for hyperentangled states

We show that bipartite Bell inequalities based on the Einstein-Podolsky-Rosen criterion for elements of reality and derived from the properties of some hyperentangled states allow feasible experimental verifications of the fact that quantum nonlocality grows exponentially with the size of the subsystems, and Bell loophole-free tests with currently available photodetection efficiencies.Comment: REVTeX4, 5 page

Doprinosi dodatnih raspršenja međudjelovanju u konačnom stanju u (e, e ˇ ′p) reakcijama

A semiclassical model is employed to study the effects of rescattering on (e,e˘p) cross sections. We consider a two-step process with the propagation of an intermediate nucleon and use Glauber theory to account for the effects of N-N scattering. This calculation has relevance for the analysis of data at high missing energies. Of particular interest is the E97-006 experiment done at JLab. It is found that rescattering is strongly reduced in parallel kinematics and that the excitation of nucleon resonances is likely to give important contributions to the final-state interactions in the correlated region.Primjenjujemo poluklasičan model za proučavanje učinaka dodatnih raspršenja u udarnim presjecima reakcija (e,e′p). Razmatramo dvostruki proces s gibanjem međunukleona, a učinke N–N raspršenja uključujemo prema Glauberovoj teoriji. Ovi su računi važni za analize podataka pri velikim manjkovima energije. Posebno je zanimljivo mjerenje E97-006 u JLaboratoriju. Nalazimo jako smanjenje dodatnih raspršenja u usporednoj kinematici te vjerojatno velike doprinose od uzbude nukleonskih rezonancija međudjelovanju u konačnom stanju u koreliranom području

Doprinosi dodatnih raspršenja međudjelovanju u konačnom stanju u (e, e ˇ ′p) reakcijama

A semiclassical model is employed to study the effects of rescattering on (e,e˘p) cross sections. We consider a two-step process with the propagation of an intermediate nucleon and use Glauber theory to account for the effects of N-N scattering. This calculation has relevance for the analysis of data at high missing energies. Of particular interest is the E97-006 experiment done at JLab. It is found that rescattering is strongly reduced in parallel kinematics and that the excitation of nucleon resonances is likely to give important contributions to the final-state interactions in the correlated region.Primjenjujemo poluklasičan model za proučavanje učinaka dodatnih raspršenja u udarnim presjecima reakcija (e,e′p). Razmatramo dvostruki proces s gibanjem međunukleona, a učinke N–N raspršenja uključujemo prema Glauberovoj teoriji. Ovi su računi važni za analize podataka pri velikim manjkovima energije. Posebno je zanimljivo mjerenje E97-006 u JLaboratoriju. Nalazimo jako smanjenje dodatnih raspršenja u usporednoj kinematici te vjerojatno velike doprinose od uzbude nukleonskih rezonancija međudjelovanju u konačnom stanju u koreliranom području

Quasiparticles in Neon using the Faddeev Random Phase Approximation

The spectral function of the closed-shell Neon atom is computed by expanding the electron self-energy through a set of Faddeev equations. This method describes the coupling of single-particle degrees of freedom with correlated two-electron, two-hole, and electron-hole pairs. The excitation spectra are obtained using the Random Phase Approximation, rather than the Tamm-Dancoff framework employed in the third-order algebraic diagrammatic contruction [ADC(3)] method. The difference between these two approaches is studied, as well as the interplay between ladder and ring diagrams in the self-energy. Satisfactory results are obtained for the ionization energies as well as the energy of the ground state with the Faddeev-RPA scheme that is also appropriate for the high-density electron gas.Comment: Revised manuscript. The working equations of the Faddeev-RPA method are included in the Appendi