22,435 research outputs found
An alternative approach concerning Elko spinors and the hidden unitarity
In this theoretical communication we look towards understand the underlying
phenomenology concerning the Elko spinors within VSR theory. The program to be
accomplished here start when we define the eigenspinors of the charge
conjugation operator as eigenstates of the helicity operator in the Cartesian
coordinates system. This prescription is very useful in the sense of
phenomenological point of view, so, we propose a set of Elko spinors ready to
be computationally implemented. Regardless of, in order to show the application
of given approach we impose to these spinors to be restrict to an axis,
coincidentally the axis of locality, and then, using the proposed prescription,
we search for physical amounts and physical processes by analysing the Yukawa
and the self-interaction in such framework.Comment: 10 pages, 2 figures. Accepted for publication in AAC
Born-Infeld magnetars: larger than classical toroidal magnetic fields and implications for gravitational-wave astronomy
Magnetars are neutron stars presenting bursts and outbursts of X- and
soft-gamma rays that can be understood with the presence of very large magnetic
fields. Thus, nonlinear electrodynamics should be taken into account for a more
accurate description of such compact systems. We study that in the context of
ideal magnetohydrodynamics and make a realization of our analysis to the case
of the well-known Born-Infeld (BI) electromagnetism in order to come up with
some of its astrophysical consequences. We focus here on toroidal magnetic
fields as motivated by already known magnetars with low dipolar magnetic fields
and their expected relevance in highly magnetized stars. We show that BI
electrodynamics leads to larger toroidal magnetic fields when compared to
Maxwell's electrodynamics. Hence, one should expect higher production of
gravitational waves (GWs) and even more energetic giant flares from nonlinear
stars. Given current constraints on BI's scale field, giant flare energetics
and magnetic fields in magnetars, we also find that the maximum magnitude of
magnetar ellipticities should be . Besides, BI electrodynamics
may lead to a maximum increase of order of the GW energy radiated
from a magnetar when compared to Maxwell's, while much larger percentages may
arise for other physically motivated scenarios. Thus, nonlinear theories of the
electromagnetism might also be probed in the near future with the improvement
of GW detectors.Comment: 8 pages, no figures, accepted for publication in The European
Physical Journal C (EPJC
On the nature of some SGRs and AXPs as rotation-powered neutron stars
We investigate the possibility that some SGRs/AXPs could be canonical
rotation-powered pulsars using realistic NS structure parameters instead of
fiducial values. We show that realistic NS parameters lowers the estimated
value of the magnetic field and radiation efficiency, ,
with respect to estimates based on fiducial NS parameters. We show that nine
SGRs/AXPs can be described as canonical pulsars driven by the NS rotational
energy, for computed in the soft (2--10~keV) X-ray band. We compute the
range of NS masses for which . We discuss the observed
hard X-ray emission in three sources of the group of nine potentially
rotation-powered NSs. This additional hard X-ray component dominates over the
soft one leading to in two of them. We show that 9
SGRs/AXPs can be rotation-powered NSs if we analyze their X-ray luminosity in
the soft 2--10~keV band. Interestingly, four of them show radio emission and
six have been associated with supernova remnants (including Swift J1834.9-0846
the first SGR observed with a surrounding wind nebula). These observations give
additional support to our results of a natural explanation of these sources in
terms of ordinary pulsars. Including the hard X-ray emission observed in three
sources of the group of potential rotation-powered NSs, this number of sources
with becomes seven. It remains open to verification
1) the accuracy of the estimated distances and 2) the possible contribution of
the associated supernova remnants to the hard X-ray emission.Comment: 11 pages, 14 figures, to appear in A&
Influência dos fatores edáficos no crescimento da Bertholletia excelsa H.B.K. na Amazônia.
O objetivo deste trabalho foi determinar a influência dos fatores edáficos (fÃsicos e quÃmicos) na variabilidade do crescimento da Bertholletia excelsa H.B.K. (castanheira-do-brasil) em distintas condições de solo na Amazônia
Teste de germinação in vitro de embriões zigóticos de dendezeiro.
Este trabalho teve como objetivo avaliar a germinação e a viabilidade de sementes de E. guineensis, por meio de ensaios in vitro e teste de tetrazólio de embriões zigóticos
- …