5,582 research outputs found
Quantum Non-Gravity and Stellar Collapse
Observational indications combined with analyses of analogue and emergent
gravity in condensed matter systems support the possibility that there might be
two distinct energy scales related to quantum gravity: the scale that sets the
onset of quantum gravitational effects (related to the Planck scale) and
the much higher scale signalling the breaking of Lorentz symmetry. We
suggest a natural interpretation for these two scales: is the energy
scale below which a special relativistic spacetime emerges, is the scale
below which this spacetime geometry becomes curved. This implies that the first
`quantum' gravitational effect around could simply be that gravity is
progressively switched off, leaving an effective Minkowski quantum field theory
up to much higher energies of the order of . This scenario may have
important consequences for gravitational collapse, inasmuch as it opens up new
possibilities for the final state of stellar collapse other than an evaporating
black hole.Comment: 6 pages, 2 figures. v2: Partially restructured; potentially
observable consequence added. Several clarifications + 3 new references. To
appear in Found. of Phy
Does the Sun Shine by pp or CNO Fusion Reactions?
We show that solar neutrino experiments set an upper limit of 7.8% (7.3%
including the recent KamLAND measurements) to the fraction of energy that the
Sun produces via the CNO fusion cycle, which is an order of magnitude
improvement upon the previous limit. New experiments are required to detect CNO
neutrinos corresponding to the 1.5% of the solar luminosity that the standard
solar model predicts is generated by the CNO cycle.Comment: Background information at http://www.sns.ias.edu/~jn
Solar Neutrinos
The study of solar neutrinos has given since ever a fundamental contribution
both to astroparticle and to elementary particle physics, offering an ideal
test of solar models and offering at the same time relevant indications on the
fundamental interactions among particles. After reviewing the striking results
of the last two decades, which were determinant to solve the long standing
solar neutrino puzzle and refine the Standard Solar Model, we focus our
attention on the more recent results in this field and on the experiments
presently running or planned for the near future. The main focus at the moment
is to improve the knowledge of the mass and mixing pattern and especially to
study in detail the lowest energy part of the spectrum, which represents most
of solar neutrino spectrum but is still a partially unexplored realm. We
discuss this research project and the way in which present and future
experiments could contribute to make the theoretical framemork more complete
and stable, understanding the origin of some "anomalies" that seem to emerge
from the data and contributing to answer some present questions, like the exact
mechanism of the vacuum to matter transition and the solution of the so called
solar metallicity problem.Comment: 51 pages, to be published in Special Issue on Neutrino Physics,
Advances in High Energy Physics Hindawi Publishing Corporation 201
Quasi-normal mode analysis in BEC acoustic black holes
We perform a quasi-normal mode analysis of black hole configurations in
Bose-Einstein condensates (BEC). In this analysis we use the full Bogoliubov
dispersion relation, not just the hydrodynamic or geometric approximation. We
restrict our attention to one-dimensional flows in BEC with step-like
discontinuities. For this case we show that in the hydrodynamic approximation
quasi-normal modes do not exist. The full dispersion relation, however, allows
the existence of quasi-normal modes. Remarkably, the spectrum of these modes is
not discrete but continuous.Comment: 7 pages, 3 figure
Global Analysis of Solar Neutrino Oscillations Including SNO CC Measurement
For active and sterile neutrinos, we present the globally allowed solutions
for two neutrino oscillations. We include the SNO CC measurement and all other
relevant solar neutrino and reactor data. Five active neutrino oscillation
solutions (LMA, LOW, SMA, VAC, and Just So2) are currently allowed at 3 sigma;
three sterile neutrino solutions (Just So2, SMA, and VAC) are allowed at 3
sigma. The goodness of fit is satisfactory for all eight solutions. We also
investigate the robustness of the allowed solutions by carrying out global
analyses with and without: 1) imposing solar model constraints on the 8B
neutrino flux, 2) including the Super-Kamiokande spectral energy distribution
and day-night data, 3) including a continuous mixture of active and sterile
neutrinos, 4) using an enhanced CC cross section for deuterium (due to
radiative corrections), and 5) a optimistic, hypothetical reduction by a factor
of three of the error of the SNO CC rate. For every analysis strategy used in
this paper, the most favored solutions all involve large mixing angles: LMA,
LOW, or VAC. The favored solutions are robust, but the presence at 3 sigma of
individual sterile solutions and the active Just So2 solution is sensitive to
the analysis assumptions.Comment: 9 figures, higher resolution versions at http://www.sns.ias.edu/~jnb,
added references and clarification
Solar Neutrinos Before and After Neutrino 2004
We compare, using a three neutrino analysis, the allowed neutrino oscillation
parameters and solar neutrino fluxes determined by the experimental data
available Before and After Neutrino 2004. New data available after Neutrino2004
include refined KamLAND and gallium measurements. We use six different
approaches to analyzing the KamLAND data. We present detailed results using all
the available neutrino and anti-neutrino data for Delta m^2_{12}, tan^2
theta_{12}, sin^2 theta_{13}, and sin^2 eta (sterile fraction). Using the same
complete data sets, we also present Before and After determinations of all the
solar neutrino fluxes, which are treated as free parameters, an upper limit to
the luminosity fraction associated with CNO neutrinos, and the predicted rate
for a 7Be solar neutrino experiment. The 1 sigma (3 sigma) allowed range of
Delta m^2_{21} = (8.2 +- 0.3) (^+1.0_-0.8)times 10^{-5} eV^2 is decreased by a
factor of 1.7 (5), but the allowed ranges of all other neutrino oscillation
parameters and neutrino fluxes are not significantly changed. Maximal mixing is
disfavored at 5.8 sigma and the bound on the mixing angle theta_{13} is
slightly improved to sin^2 theta_{13}<0.048 at 3 sigma. The predicted rate in a
7Be neutrino-electron scattering experiment is (0.665 +-0.015) of the rate
implied by the BP04 solar model in the absence of neutrino oscillations. The
corresponding predictions for p-p and pep experiments are, respectively, 0.707
{+0.011}{-0.013} and 0.644 {+0.011}{-0.013}. We derive upper limits to CPT
violation in the weak sector by comparing reactor anti-neutrino oscillation
parameters with neutrino oscillation parameters. We also show that the recent
data disfavor at 91 % CL a proposed non-standard interaction description of
solar neutrino oscillations.Comment: Added predictions for p-p and pep neutrino-electron scattering rate;
publishe
Global three-neutrino oscillation analysis of neutrino data
A global analysis of the solar, atmospheric and reactor neutrino data is
presented in terms of three-neutrino oscillations. We include the most recent
solar neutrino rates of Homestake, SAGE, GALLEX and GNO, as well as the recent
1117 day Super-Kamiokande data sample, including the recoil electron energy
spectrum both for day and night periods and we treat in a unified way the full
parameter space for oscillations, correctly accounting for the transition from
the matter enhanced (MSW) to the vacuum oscillations regime. Likewise, we
include in our description conversions with . For the
atmospheric data we perform our analysis of the contained events and the
upward-going -induced muon fluxes, including the previous data samples of
Frejus, IMB, Nusex, and Kamioka experiments as well as the full 71 kton-yr
(1144 days) Super-Kamiokande data set, the recent 5.1 kton-yr contained events
of Soudan2 and the results on upgoing muons from the MACRO detector. We first
present the allowed regions of solar and atmospheric oscillation parameters
, and , ,
respectively, as a function of and determine the constraints from
atmospheric and solar data on the mixing angle , common to solar
and atmospheric analyses. We also obtain the allowed ranges of parameters from
the full five-dimensional combined analysis of the solar, atmospheric and
reactor data.Comment: 56 pages, 21 postscript figures. Some misprints corrected and new
references added. Chooz limit included in Fig.21. Final version to appear in
Phys. Rev.
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