3,273 research outputs found
Neutrino scattering and flavor transformation in supernovae
We argue that the small fraction of neutrinos that undergo direction-changing
scattering outside of the neutrinosphere could have significant influence on
neutrino flavor transformation in core-collapse supernova environments. We show
that the standard treatment for collective neutrino flavor transformation is
adequate at late times, but could be inadequate in the crucial shock
revival/explosion epoch of core-collapse supernovae, where the potentials that
govern neutrino flavor evolution are affected by the scattered neutrinos.
Taking account of this effect, and the way it couples to entropy and
composition, will require a new paradigm in supernova modeling.Comment: 5 pages, 3 figure
Halo Modification of a Supernova Neutronization Neutrino Burst
We give the first self-consistent calculation of the effect of the scattered
neutrino halo on flavor evolution in supernovae. Our example case is an O-Ne-Mg
core collapse supernova neutronization neutrino burst. We find that the
addition of the halo neutrinos produces qualitative and quantitative changes in
the final flavor states of neutrinos. We also find that the halo neutrinos
produce a novel distortion of the neutrino flavor swap. Our results provide
strong motivation for tackling the full multidimensional and
composition-dependent aspects of this problem in the future.Comment: 14 pages, 13 figures, 1 tabl
Using airborne LiDAR Survey to explore historic-era archaeological landscapes of Montserrat in the eastern Caribbean
This article describes what appears to be the first archaeological application of airborne LiDAR survey to historic-era landscapes in the Caribbean archipelago, on the island of Montserrat. LiDAR is proving invaluable in extending the reach of traditional pedestrian survey into less favorable areas, such as those covered by dense neotropical forest and by ashfall from the past two decades of active eruptions by the Soufrière Hills volcano, and to sites in localities that are inaccessible on account of volcanic dangers. Emphasis is placed on two aspects of the research: first, the importance of ongoing, real-time interaction between the LiDAR analyst and the archaeological team in the field; and second, the advantages of exploiting the full potential of the three-dimensional LiDAR point cloud data for purposes of the visualization of archaeological sites and features
Mode signature and stability for a Hamiltonian model of electron temperature gradient turbulence
Stability properties and mode signature for equilibria of a model of electron
temperature gradient (ETG) driven turbulence are investigated by Hamiltonian
techniques. After deriving the infinite families of Casimir invariants,
associated with the noncanonical Poisson bracket of the model, a sufficient
condition for stability is obtained by means of the Energy-Casimir method. Mode
signature is then investigated for linear motions about homogeneous equilibria.
Depending on the sign of the equilibrium "translated" pressure gradient, stable
equilibria can either be energy stable, i.e.\ possess definite linearized
perturbation energy (Hamiltonian), or spectrally stable with the existence of
negative energy modes (NEMs). The ETG instability is then shown to arise
through a Kre\u{\i}n-type bifurcation, due to the merging of a positive and a
negative energy mode, corresponding to two modified drift waves admitted by the
system. The Hamiltonian of the linearized system is then explicitly transformed
into normal form, which unambiguously defines mode signature. In particular,
the fast mode turns out to always be a positive energy mode (PEM), whereas the
energy of the slow mode can have either positive or negative sign
Density Fluctuation Effects on Collective Neutrino Oscillations in O-Ne-Mg Core-Collapse Supernovae
We investigate the effect of matter density fluctuations on supernova
collective neutrino flavor oscillations. In particular, we use full
multi-angle, 3-flavor, self-consistent simulations of the evolution of the
neutrino flavor field in the envelope of an O-Ne-Mg core collapse supernova at
shock break-out (neutrino neutronization burst) to study the effect of the
matter density "bump" left by the He-burning shell. We find a seemingly
counterintuitive increase in the overall electron neutrino survival probability
created by this matter density feature. We discuss this behavior in terms of
the interplay between the matter density profile and neutrino collective
effects. While our results give new insights into this interplay, they also
suggest an immediate consequence for supernova neutrino burst detection: it
will be difficult to use a burst signal to extract information on fossil
burning shells or other fluctuations of this scale in the matter density
profile. Consistent with previous studies, our results also show that the
interplay of neutrino self-coupling and matter fluctuation could cause a
significant increase in the electron neutrino survival probability at very low
energyComment: 12 pages, 11 figures. This is a pre-submission version of the pape
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