1,547 research outputs found
Parallel Search with no Coordination
We consider a parallel version of a classical Bayesian search problem.
agents are looking for a treasure that is placed in one of the boxes indexed by
according to a known distribution . The aim is to minimize
the expected time until the first agent finds it. Searchers run in parallel
where at each time step each searcher can "peek" into a box. A basic family of
algorithms which are inherently robust is \emph{non-coordinating} algorithms.
Such algorithms act independently at each searcher, differing only by their
probabilistic choices. We are interested in the price incurred by employing
such algorithms when compared with the case of full coordination. We first show
that there exists a non-coordination algorithm, that knowing only the relative
likelihood of boxes according to , has expected running time of at most
, where is the expected running time of the best
fully coordinated algorithm. This result is obtained by applying a refined
version of the main algorithm suggested by Fraigniaud, Korman and Rodeh in
STOC'16, which was designed for the context of linear parallel search.We then
describe an optimal non-coordinating algorithm for the case where the
distribution is known. The running time of this algorithm is difficult to
analyse in general, but we calculate it for several examples. In the case where
is uniform over a finite set of boxes, then the algorithm just checks boxes
uniformly at random among all non-checked boxes and is essentially times
worse than the coordinating algorithm.We also show simple algorithms for Pareto
distributions over boxes. That is, in the case where for
, we suggest the following algorithm: at step choose uniformly
from the boxes unchecked in ,
where . It turns out this algorithm is asymptotically
optimal, and runs about times worse than the case of full coordination
Quark cluster signatures in deuteron electromagnetic interactions
A suggestion is made for distinguishing 2N and 6q short range correlations
within the deuteron. The suggestion depends upon observing high momentum
backward nucleons emerging from inelastic electromagnetic scattering from a
deuteron target. A simple model is worked out to see the size of effects that
may be expected.Comment: 18 pages (3 figures available as hard copy), WM-94-10
Measurement of the double-\beta decay half-life of ^{136}Xe with the KamLAND-Zen experiment
We present results from the KamLAND-Zen double-beta decay experiment based on
an exposure of 77.6 days with 129 kg of Xe. The measured two-neutrino
double-beta decay half-life of Xe is yr, consistent with a recent
measurement by EXO-200. We also obtain a lower limit for the neutrinoless
double-beta decay half-life, yr at 90%
confidence level (C.L.), which corresponds to almost a five-fold improvement
over previous limits.Comment: 6 pages, 4 figures. Version as published in PR
Study of electron anti-neutrinos associated with gamma-ray bursts using KamLAND
We search for electron anti-neutrinos () from long and
short-duration gamma-ray bursts~(GRBs) using data taken by the KamLAND detector
from August 2002 to June 2013. No statistically significant excess over the
background level is found. We place the tightest upper limits on
fluence from GRBs below 7 MeV and place first constraints on
the relation between luminosity and effective temperature.Comment: 16 pages and 5 figure
KamLAND Sensitivity to Neutrinos from Pre-Supernova Stars
In the late stages of nuclear burning for massive stars (M>8~M_{\sun}), the
production of neutrino-antineutrino pairs through various processes becomes the
dominant stellar cooling mechanism. As the star evolves, the energy of these
neutrinos increases and in the days preceding the supernova a significant
fraction of emitted electron anti-neutrinos exceeds the energy threshold for
inverse beta decay on free hydrogen. This is the golden channel for liquid
scintillator detectors because the coincidence signature allows for significant
reductions in background signals. We find that the kiloton-scale liquid
scintillator detector KamLAND can detect these pre-supernova neutrinos from a
star with a mass of 25~M_{\sun} at a distance less than 690~pc with 3
significance before the supernova. This limit is dependent on the neutrino mass
ordering and background levels. KamLAND takes data continuously and can provide
a supernova alert to the community.Comment: 19 pages, 6 figures, 1 tabl
A compact ultra-clean system for deploying radioactive sources inside the KamLAND detector
We describe a compact, ultra-clean device used to deploy radioactive sources
along the vertical axis of the KamLAND liquid-scintillator neutrino detector
for purposes of calibration. The device worked by paying out and reeling in
precise lengths of a hanging, small-gauge wire rope (cable); an assortment of
interchangeable radioactive sources could be attached to a weight at the end of
the cable. All components exposed to the radiopure liquid scintillator were
made of chemically compatible UHV-cleaned materials, primarily stainless steel,
in order to avoid contaminating or degrading the scintillator. To prevent radon
intrusion, the apparatus was enclosed in a hermetically sealed housing inside a
glove box, and both volumes were regularly flushed with purified nitrogen gas.
An infrared camera attached to the side of the housing permitted real-time
visual monitoring of the cable's motion, and the system was controlled via a
graphical user interface.Comment: Revised author affiliations, corrected typos, made minor improvements
to text, and revised reference
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