497 research outputs found
Neutrinos Have Mass - So What?
In this brief review, I discuss the new physics unveiled by neutrino
oscillation experiments over the past several years, and discuss several
attempts at understanding the mechanism behind neutrino masses and lepton
mixing. It is fair to say that, while significant theoretical progress has been
made, we are yet to construct a coherent picture that naturally explains
non-zero, yet tiny, neutrino masses and the newly revealed, puzzling patterns
of lepton mixing. I discuss what the challenges are, and point to the fact that
more experimental input (from both neutrino and non-neutrino experiments) is
dearly required - and that new data is expected to reveal, in the next several
years, new information. Finally, I draw attention to the fact that neutrinos
may have only just begun to reshape fundamental physics, given the fact that we
are still to explain the LSND anomaly and because the neutrino oscillation
phenomenon is ultimately sensitive to very small new-physics effects.Comment: invited brief review, 15 pages, 1 eps figure, typo corrected,
reference adde
The Physical Range of Majorana Neutrino Mixing Parameters
If neutrinos are Majorana fermions, the lepton mixing parameter space
consists of six mixing parameters: three mixing angles and three CP-odd phases.
A related issue concerns the physical range of the mixing parameters. What
values should these take so that all physically distinguishable mixing
scenarios are realized? We present a detailed discussion of the lepton mixing
parameter space in the case of two and three active neutrinos, and in the case
of three active and N sterile neutrinos. We emphasize that this question, which
has been a source of confusion even among "neutrino" physicists, is connected
to an unambiguous definition of the neutrino mass eigenstates. We find that all
Majorana phases can always be constrained to lie between 0 and pi, and that all
mixing angles can be chosen positive and at most less than or equal to pi/2
provided the Dirac phases are allowed to vary between -pi and pi. We illustrate
our results with several examples. Finally, we point out that, in the case of
new flavor-changing neutrino interactions, the lepton mixing parameter space
may need to be enlarged. We properly qualify this statement, and offer concrete
examples.Comment: 16 pages, 2 .eps figures, references added, minor typos correcte
Low Temperature Static and Dynamic Behavior of the Two-Dimensional Easy-Axis Heisenberg Model
We apply the self-consistent harmonic approximation (SCHA) to study static
and dynamic properties of the two-dimensional classical Heisenberg model with
easy-axis anisotropy. The static properties obtained are magnetization and spin
wave energy as functions of temperature, and the critical temperature as a
function of the easy-axis anisotropy. We also calculate the dynamic correlation
functions using the SCHA renormalized spin wave energy. Our analytical results,
for both static properties and dynamic correlation functions, are compared to
numerical simulation data combining cluster-Monte Carlo algorithms and Spin
Dynamics. The comparison allows us to conclude that far below the transition
temperature, where the SCHA is valid, spin waves are responsible for all
relevant features observed in the numerical simulation data; topological
excitations do not seem to contribute appreciably. For temperatures closer to
the transition temperature, there are differences between the dynamic
correlation functions from SCHA theory and Spin Dynamics; these may be due to
the presence of domain walls and solitons.Comment: 12 pages, 14 figure
Efeito do pré-tratamento enzimåtico no teor de antocianinas do suco de amora-preta processado por microfiltração.
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.).
Effect of enzymatic treatment, shear stress and temperature on the rheological behavior of blackberry (Rubus spp.) juice.
Identificação das antocianinas majoritårias na casca de uva tinta sem semente utilizando CLUE-ESI-EM/EM.
Caracterização e avaliação do teor de antocianinas do suco de romã (Punica granatum L.).
Estudo de compostos de valor agregado presentes no resĂduo gerado apĂłs o processo de microfiltração do açaĂ.
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