1,173 research outputs found
Updating the parameters of a threshold scheme by minimal broadcast
Threshold schemes allow secret data to be protected among a set of participants in such a way that only a prespecified threshold of participants can reconstruct the secret from private information (shares) distributed to them on a system setup using secure channels. We consider the general problem of designing unconditionally secure threshold schemes whose defining parameters (the threshold and the number of participants) can later be changed by using only public channel broadcast messages. In this paper, we are interested in the efficiency of such threshold schemes, and seek to minimize storage costs (size of shares) as well as optimize performance in low-bandwidth environments by minimizing the size of necessary broadcast messages. We prove a number of lower bounds on the smallest size of broadcast message necessary to make general changes to the parameters of a threshold scheme in which each participant already holds shares of minimal size. We establish the tightness of these bounds by demonstrating optimal schemes.S. G. Barwick, Wen-Ai Jackson and Keith M. Marti
Inference for Parameters Defined by Moment Inequalities: A Recommended Moment Selection Procedure
This paper is concerned with tests and confi dence intervals for parameters that are
not necessarily identifi ed and are de fined by moment inequalities. In the literature,
different test statistics, critical value methods, and implementation methods (i.e., the
asymptotic distribution versus the bootstrap) have been proposed. In this paper, we
compare these methods. We provide a recommended test statistic, moment selection
critical value method, and implementation method. We provide data-dependent procedures for choosing the key moment selection tuning parameter kappa and a size-correction
factor eta.National Science Foundation (U.S.) (grant SES-0751517
Updating the Parameters of a Threshold Scheme by Minimal Broadcast
Threshold schemes allow secret data to be protected amongst a set
of participants in such a way that only a pre-specified threshold
of participants can reconstruct the secret from private
information (shares) distributed to them on system setup using
secure channels. We consider the general problem of designing
unconditionally secure
threshold schemes whose defining parameters (the threshold and the
number of participants) can later be changed by using only public
channel broadcast messages. In this paper we are interested in the
efficiency of such threshold schemes, and seek to minimise storage
costs (size of shares) as well as optimise performance in low
bandwidth environments by minimising the size of necessary
broadcast messages. We prove a number of lower bounds on the
smallest size of broadcast message necessary to make general
changes to the parameters of a threshold scheme in which each
participant already holds shares of minimal size. We establish the
tightness of these bounds by demonstrating optimal schemes
Energy Spectra, Altitude Profiles and Charge Ratios of Atmospheric Muons
We present a new measurement of air shower muons made during atmospheric
ascent of the High Energy Antimatter Telescope balloon experiment. The muon
charge ratio mu+ / mu- is presented as a function of atmospheric depth in the
momentum interval 0.3-0.9 GeV/c. The differential mu- momentum spectra are
presented between 0.3 and about 50 GeV/c at atmospheric depths between 13 and
960 g/cm^2. We compare our measurements with other recent data and with Monte
Carlo calculations of the same type as those used in predicting atmospheric
neutrino fluxes. We find that our measured mu- fluxes are smaller than the
predictions by as much as 70% at shallow atmospheric depths, by about 20% at
the depth of shower maximum, and are in good agreement with the predictions at
greater depths. We explore the consequences of this on the question of
atmospheric neutrino production.Comment: 11 pages, 8 figures, to appear in Phys. Rev. D (2000
Neutrino production through hadronic cascades in AGN accretion disks
We consider the production of neutrinos in active galactic nuclei (AGN)
through hadronic cascades. The initial, high energy nucleons are accelerated in
a source above the accretion disk around the central black hole. From the
source, the particles diffuse back to the disk and initiate hadronic cascades.
The observable output from the cascade are electromagnetic radiation and
neutrinos. We use the observed diffuse background X-ray luminosity, which
presumably results {}from this process, to predict the diffuse neutrino flux
close to existing limits from the Frejus experiment. The resulting neutrino
spectrum is down to the \GeV region. We discuss modifications of
this scenario which reduce the predicted neutrino flux.Comment: 12 Pages, LaTeX, TK 92 0
Majorana Neutrinos and Gravitational Oscillation
We analyze the possibility of encountering resonant transitions of high
energy Majorana neutrinos produced in Active Galactic Nuclei (AGN). We consider
gravitational, electromagnetic and matter effects and show that the latter are
ignorable. Resonant oscillations due to the gravitational interactions are
shown to occur at energies in the PeV range for magnetic moments in the
range. Coherent precession will dominate for larger magnetic
moments. The alllowed regions for gravitational resonant transitions are
obtained.Comment: 11 pages, 8 figures, Latex; requires revtex and epsf.tex submitted to
Physical Review
Performance of the AMS-02 Transition Radiation Detector
For cosmic particle spectroscopy on the International Space Station the AMS
experiment will be equipped with a Transition Radiation Detector (TRD) to
improve particle identification. The TRD has 20 layers of fleece radiator with
Xe/CO2 proportional mode straw tube chambers. They are supported in a conically
shaped octagon structure made of CFC-Al-honeycomb. For low power consumption VA
analog multiplexers are used as front-end readout. A 20 layer prototype built
from final design components has achieved proton rejections from 100 to 2000 at
90% electron efficiency for proton beam energies up to 250 GeV with cluster
counting, likelihood and neural net selection algorithms.Comment: 11 pages, 25 figures, espcrc2.sty (elsevier 2-column
Neutrino Interactions at Ultrahigh Energies
We report new calculations of the cross sections for deeply inelastic
neutrino-nucleon scattering at neutrino energies between 10^{9}\ev and
10^{21}\ev. We compare with results in the literature and assess the
reliability of our predictions. For completeness, we briefly review the cross
sections for neutrino interactions with atomic electrons, emphasizing the role
of the -boson resonance in interactions for neutrino
energies in the neighborhood of 6.3\pev. Adopting model predictions for
extraterrestrial neutrino fluxes from active galactic nuclei, gamma-ray
bursters, and the collapse of topological defects, we estimate event rates in
large-volume water \v{C}erenkov detectors and large-area ground arrays.Comment: 32 pages, 11 figures, uses RevTeX and boxedep
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