610 research outputs found
Large Mixing Induced by the Strong Coupling with a Single Bulk Neutrinos
Neutrino is a good probe of extra dimensions. Large mixing and the apparent
lack of very complicated oscillation patterns may be an indication of large
couplings between the brane and a single bulk neutrino. A simple and realistic
five-dimensional model of this kind is discussed. It requires a sterile in
addition to three active neutrinos on the brane, all coupled strongly to one
common bulk neutrino, but not directly among themselves. Mindful that sterile
neutrinos are disfavored in the atmospheric and solar data, we demand induced
mixing to occur among the active neutrinos, but not between the active and the
sterile. The size of the extra dimension is arbitrary in this model,
otherwise it contains six parameters which can be used to fit the three
neutrino masses and the three mixing angles. However, in the model those six
parameters must be suitably ordered, so a successful fit is not guaranteed. It
turns out that not only the data can be fitted, but as a result of the
ordering, a natural connection between the smallness of the reactor angle
and the smallness of the mass-gap ratio can be derived.Comment: Misprints above eq. (22) corrected. To appear in PR
N-body simulations of galaxies and groups of galaxies with the Marseille GRAPE systems
I review the Marseille GRAPE systems and the N-body simulations done with
them. I first describe briefly the available hardware and software, their
possibilities and their limitations. I then describe work done on interacting
galaxies and groups of galaxies. This includes simulations of the formation of
ring galaxies, simulations of bar destruction by massive compact satellites, of
merging in compact groups and of the formation of brightest members in clusters
of galaxies.Comment: 13 pages, 5 figures, to be published in "Non-linear Dynamics and
Chaos in Astrophysics", eds. J.R. Buchler, S. Gottesman, J. Hunter and H.
Kandrup, Annals of the New York Academy of Science
Properties of pattern formation and selection processes in nonequilibrium systems with external fluctuations
We extend the phase field crystal method for nonequilibrium patterning to
stochastic systems with external source where transient dynamics is essential.
It was shown that at short time scales the system manifests pattern selection
processes. These processes are studied by means of the structure function
dynamics analysis. Nonequilibrium pattern-forming transitions are analyzed by
means of numerical simulations.Comment: 15 poages, 8 figure
Changes in nasal airflow and heat transfer correlate with symptom improvement after surgery for nasal obstruction
Surgeries to correct nasal airway obstruction (NAO) often have less than desirable outcomes, partly due to the absence of an objective tool to select the most appropriate surgical approach for each patient. Computational fluid dynamics (CFD) models can be used to investigate nasal airflow, but variables need to be identified that can detect surgical changes and correlate with patient symptoms. CFD models were constructed from pre- and post-surgery computed tomography scans for 10 NAO patients showing no evidence of nasal cycling. Steady-state inspiratory airflow, nasal resistance, wall shear stress, and heat flux were computed for the main nasal cavity from nostrils to posterior nasal septum both bilaterally and unilaterally. Paired t-tests indicated that all CFD variables were significantly changed by surgery when calculated on the most obstructed side, and that airflow, nasal resistance, and heat flux were significantly changed bilaterally as well. Moderate linear correlations with patient-reported symptoms were found for airflow, heat flux, unilateral allocation of airflow, and unilateral nasal resistance as a fraction of bilateral nasal resistance when calculated on the most obstructed nasal side, suggesting that these variables may be useful for evaluating the efficacy of nasal surgery objectively. Similarity in the strengths of these correlations suggests that patient-reported symptoms may represent a constellation of effects and that these variables should be tracked concurrently during future virtual surgery planning
Oscillation Induced Neutrino Asymmetry Growth in the Early Universe
We study the dynamics of active-sterile neutrino oscillations in the early
universe using full momentum-dependent quantum-kinetic equations. These
equations are too complicated to allow for an analytical treatment, and
numerical solution is greatly complicated due to very pronounced and narrow
structures in the momentum variable introduced by resonances. Here we introduce
a novel dynamical discretization of the momentum variable which overcomes this
problem. As a result we can follow the evolution of neutrino ensemble
accurately well into the stable growing phase. Our results confirm the
existence of a "chaotic region" of mixing parameters, for which the final sign
of the asymmetry, and hence the SBBN prediction of He(4)-abundance cannot be
accurately determined.Comment: 23 pages, 9 eps-figs, Latex, uses JHEP clas
Constraining neutrino oscillation parameters with current solar and atmospheric data
We analyze the impact of recent solar, atmospheric and reactor data in the
determination of the neutrino oscillation parameters, taking into account that
both the solar nu_e and the atmospheric nu_mu may convert to a mixture of
active and sterile neutrinos. We use the most recent global solar neutrino
data, including the 1496-day Super-K neutrino data sample, and we investigate
in detail the impact of the SNO neutral current, spectral and day/night data by
performing also an analysis using only the charged current rate from SNO. The
implications of the first 145.1 days of KamLAND data on the determination of
the solar neutrino parameters are also discussed in detail. We confirm the
clear preference of solar+reactor data for the pure active LMA-MSW solution of
the solar neutrino problem, and obtain that the LOW, VAC, SMA and Just-So^2
solutions are disfavored with a Delta_chi^2 = 22, 22, 36, 44, respectively.
Furthermore, we find that the global solar data constrains the admixture of a
sterile neutrino to be less than 43% at 99% CL. By performing an improved fit
of the atmospheric data, we also update the corresponding regions of
oscillation parameters. We find that the recent atmospheric Super-K (1489-day)
and MACRO data have a strong impact on constraining a sterile component in
atmospheric oscillations: if the nu_mu is restricted to the atmospheric mass
states only a sterile admixture of 16% is allowed at 99% CL, while a bound of
35% is obtained in the unconstrained case. Pure sterile oscillations are
disfavored with a Delta_chi^2 = 34.6 compared to the pure active case.Comment: 28 pages, LaTeX file using RevTEX4, 12 figures and 3 tables included.
Improved version including the new KamLAND dat
Supernova Bounds on Majoron-emitting decays of light neutrinos
Neutrino masses arising from the spontaneous violation of ungauged
lepton-number are accompanied by a physical Goldstone boson, generically called
Majoron. In the high-density supernova medium the effects of Majoron-emitting
neutrino decays are important even if they are suppressed in vacuo by small
neutrino masses and/or small off-diagonal couplings. We reconsider the
influence of these decays on the neutrino signal of supernovae in the light of
recent Super-Kamiokande data on solar and atmospheric neutrinos. We find that
majoron-neutrino coupling constants in the range 3\times 10^{-7}\lsim g\lsim
2\times 10^{-5} or g \gsim 3 \times 10^{-4} are excluded by the observation
of SN1987A. Then we discuss the potential of Superkamiokande and the Sudbury
Neutrino Observatory to detect majoron neutrino interactions in the case of a
future galactic supernova. We find that these experiments could probe majoron
neutrino interactions with improved sensitivity.Comment: 28 pages, 5 figure
Confusing non-standard neutrino interactions with oscillations at a neutrino factory
Most neutrino mass theories contain non-standard interactions (NSI) of
neutrinos which can be either non-universal (NU) or flavor-changing (FC). We
study the impact of such interactions on the determination of neutrino mixing
parameters at a neutrino factory using the so-called ``golden channels''
\pnu{e}\to\pnu{\mu} for the measurement of \theta_{13}. We show that a certain
combination of FC interactions in neutrino source and earth matter can give
exactly the same signal as oscillations arising due to \theta_{13}. This
implies that information about \theta_{13} can only be obtained if bounds on
NSI are available. Taking into account the existing bounds on FC interactions,
this leads to a drastic loss in sensitivity in \theta_{13}, at least two orders
of magnitude. A near detector at a neutrino factory offers the possibility to
obtain stringent bounds on some NSI parameters. Such near site detector
constitutes an essential ingredient of a neutrino factory and a necessary step
towards the determination of \theta_{13} and subsequent study of leptonic CP
violation.Comment: 23 pages, 5 figures, improved version, accepted for publication in
Phs. Rev. D, references adde
Lepton Mixing Matrix in Standard Model Extended by One Sterile Neutrino
We consider the simplest extension of the standard electroweak model by one
sterile neutrino that allows for neutrino masses and mixing. We find that its
leptonic sector contains much less free physical parameters than previously
realized. In addition to the two neutrino masses, the lepton mixing matrix in
charged current interactions involves (n-1) free physical mixing angles for n
generations. The mixing matrix in neutral current interactions of neutrinos is
completely fixed by the two masses. Both interactions conserve CP. We
illustrate the phenomenological implications of the model by vacuum neutrino
oscillations, tritium beta decay and neutrinoless double beta decay. It turns
out that, due to the revealed specific structure in its mixing matrix, the
model with any n generations cannot accommodate simultaneously the data by
KamLAND, K2K and CHOOZ.Comment: 14 pages, no figures; version 2: (1) added a short paragraph at the
end of subsec 2.2 to record the counting of physical parameters for any
numbers of generations and sterile neutrinos for completeness; (2) added a
note in ref list, item [18] to quote and comment on an earlier work; (3)
added the second paper to ref list, item [17]; (4) fixed typo
Connecting bimaximal neutrino mixing to a light sterile neutrino
It is shown that if small neutrino masses owe their origin to the
conventional seesaw mechanism and the MNS mixing matrix is in the exact
bimaximal form, then there exist symmetries in the theory that allow one of the
righthanded neutrinos to become naturally massless, making it a candidate for
the sterile neutrino discussed in the literature. Departures from the exact
bimaximal limit leads to tiny mass for the sterile neutrino as well as its
mixing to the active neutrinos. This provides a minimal theoretical framework
where a simultaneous explanation of the solar, atmospheric and LSND
observations within the so-called 3+1 scenario may be possible.Comment: new references added; paper accepted for publication in Phys. Rev.
D.(rapid communications); note adde
- …