606 research outputs found
Vortex motion in a finite-size easy-plane ferromagnet and application to a nanodot
We study the motion of a non-planar vortex in a circular easy-plane
ferromagnet, which imitates a magnetic nanodot. Analysis was done using
numerical simulations and a new collective variable theory which includes the
coupling of Goldstone-like mode with the vortex center. Without magnetic field
the vortex follows a spiral orbit which we calculate. When a rotating in-plane
magnetic field is included, the vortex tends to a stable limit cycle which
exists in a significant range of field amplitude B and frequency for a
given system size L. For a fixed , the radius R of the orbital motion
is proportional to L while the orbital frequency varies as 1/L and is
significantly smaller than . Since the limit cycle is caused by the
interplay between the magnetization and the vortex motion, the internal mode is
essential in the collective variable theory which then gives the correct
estimate and dependency for the orbit radius . Using this
simple theory we indicate how an ac magnetic field can be used to control
vortices observed in real magnetic nanodots.Comment: 15 pages (RevTeX), 14 figures (eps
Right-handed Sneutrinos as Nonthermal Dark Matter
When the minimal supersymmetric standard model is augmented by three
right-handed neutrino superfields, one generically predicts that the neutrinos
acquire Majorana masses. We postulate that all supersymmetry (SUSY) breaking
masses as well as the Majorana masses of the right-handed neutrinos are around
the electroweak scale and, motivated by the smallness of neutrino masses,
assume that the lightest supersymmetric particle (LSP) is an almost-pure
right-handed sneutrino. We discuss the conditions under which this LSP is a
successful dark matter candidate. In general, such an LSP has to be nonthermal
in order not to overclose the universe, and we find the conditions under which
this is indeed the case by comparing the Hubble expansion rate with the rates
of the relevant thermalizing processes, including self-annihilation and
co-annihilation with other SUSY and standard model particles.Comment: 17 pages v.2: References adde
Efeito das auxinas 2,4-D, dicamba e picloram na indução de calos em embriÔes de Schizolobium parahybum.
Resumo
Efeito das citocininas BAP, TDZ e CIN na indução de calos in vitro de Schizolobium parahybum.
Pseudo-Dirac Neutrinos in the New Standard Model
The addition of gauge singlet fermions to the Standard Model Lagrangian
renders the neutrinos massive and allows one to explain all that is
experimentally known about neutrino masses and lepton mixing by varying the
values of the Majorana mass parameters M for the gauge singlets and the
neutrino Yukawa couplings. Here we explore the region of parameter space where
M values are much smaller than the neutrino Dirac masses. In this region,
neutrinos are pseudo-Dirac fermions. We find that current solar data constrain
M values to be less than at least 1E-9 eV, and discuss the sensitivity of
future experiments to tiny gauge singlet fermion masses. We also discuss a
useful basis for analyzing pseudo-Dirac neutrino mixing effects. In particular,
we identify a simple relationship between elements of M and the induced
enlarged mixing matrix and new mass-squared differences. These allow one to
directly relate bounds on the new mass-squared differences to bounds on the
singlet fermion Majorana masses.Comment: 20 Pages, 9 .eps figures, Updated reference
Deviation of Atmospheric Mixing from Maximal and Structure in the Leptonic Flavor Sector
I attempt to quantify how far from maximal one should expect the atmospheric
mixing angle to be given a neutrino mass-matrix that leads, at zeroth order, to
a nu_3 mass-eigenstate that is 0% nu_e, 50% nu_mu, and 50% nu_tau. This is done
by assuming that the solar mass-squared difference is induced by an
"anarchical" first order perturbation, an approach than can naturally lead to
experimentally allowed values for all oscillation parameters. In particular,
both |cos 2theta_atm| (the measure for the deviation of atmospheric mixing from
maximal) and |U_e3| are of order sqrt(Delta m^2_sol/Delta m^2_atm) in the case
of a normal neutrino mass-hierarchy, or of order Delta m^2_sol/Delta m^2_atm in
the case of an inverted one. Hence, if any of the textures analyzed here has
anything to do with reality, next-generation neutrino experiments can see a
nonzero cos 2theta_atm in the case of a normal mass-hierarchy, while in the
case of an inverted mass-hierarchy only neutrino factories should be able to
see a deviation of sin^2 2theta_atm from 1.Comment: 12 pages, no figures, references and acknowledgments adde
Distinction of representations via Bruhat-Tits buildings of p-adic groups
Introductory and pedagogical treatmeant of the article : P. Broussous
"Distinction of the Steinberg representation", with an appendix by Fran\c{c}ois
Court\`es, IMRN 2014, no 11, 3140-3157. To appear in Proceedings of Chaire Jean
Morlet, Dipendra Prasad, Volker Heiermann Ed. 2017. Contains modified and
simplified proofs of loc. cit. This article is written in memory of
Fran\c{c}ois Court\`es who passed away in september 2016.Comment: 33 pages, 4 figure
Caracterização e avaliação do teor de antocianinas do suco de romã (Punica granatum L.).
Avaliação por CLAE do coeficiente de rendimento das antocianinas majoritĂĄrias cianidina-3-O-glicosĂdeo e cianidina-3-rutenosĂdeo no suco clarificado de açaĂ (Euterpe oleracea Mart.).
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