15,975 research outputs found
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
Tensor product of motives via K\"unneth formula
Following Nori's original idea we here provide certain motivic categories
with a canonical tensor structure. These motivic categories are associated to a
cohomological functor on a suitable base category and the tensor structure is
induced by the cartesian tensor structure on the base category via a
cohomological K\"unneth formula.Comment: Revised version to appear on JPA
Optical phase coherent timing of the Crab nebula pulsar with Iqueye at the ESO New Technology Telescope
The Crab nebula pulsar was observed in 2009 January and December with a novel
very fast optical photon counter, Iqueye, mounted at the ESO 3.5 m New
Technology Telescope. Thanks to the exquisite quality of the Iqueye data, we
computed accurate phase coherent timing solutions for the two observing runs
and over the entire year 2009. Our statistical uncertainty on the determination
of the phase of the main pulse and the rotational period of the pulsar for
short (a few days) time intervals are s and ~0.5 ps,
respectively. Comparison with the Jodrell Bank radio ephemerides shows that the
optical pulse leads the radio one by ~240 s in January and ~160 s in
December, in agreement with a number of other measurements performed after
1996. A third-order polynomial fit adequately describes the spin-down for the
2009 January plus December optical observations. The phase noise is consistent
with being Gaussian distributed with a dispersion of s in most observations, in agreement with theoretical expectations for
photon noise-induced phase variability.Comment: 10 pages, 5 figures. Accepted for publication in Monthly Notices of
the Royal Astronomical Societ
Diminishing "charginos nearly degenerate with the lightest neutralino" slit using precision data
Though LEP II direct searches still cannot exclude a chargino nearly
degenerate with the lightest neutralino if their mass is only slightly above
half of the Z boson mass, it can be excluded indirectly analyzing precision
data. In this particular limit simple analytical formulas for oblique
electroweak radiative corrections are presented.Comment: 6 pages, latex, 2 figures included; published on PLB. Bounds on
chargino mass are improved; two references are adde
Logarithmic SUSY electroweak effects on four-fermion processes at TeV energies
We compute the MSSM one-loop contributions to the asymptotic energy behaviour
of fermion-antifermion pair production at future lepton-antilepton colliders.
Besides the conventional logarithms of Renormalization Group origin, extra SUSY
linear logarithmic terms appear of "Sudakov-type". In the TeV range their
overall effect on a variety of observables can be quite relevant and
drastically different from that obtained in the SM case.Comment: 19 pages and 14 figures, corrected version. e-mail:
[email protected]
Growth and first sexual maturation size of Gymnotus carapo (Linnaeus, 1758) in the Lobo reservoir (state of Sao Paulo, Brazil) (Pisces, Gymnotidae)
- …