149 research outputs found
Global well-posedness of the Kirchhoff equation and Kirchhoff systems
This article is devoted to review the known results on global well-posedness
for the Cauchy problem to the Kirchhoff equation and Kirchhoff systems with
small data. Similar results will be obtained for the initial-boundary value
problems in exterior domains with compact boundary. Also, the known results on
large data problems will be reviewed together with open problems.Comment: arXiv admin note: text overlap with arXiv:1211.300
P-3. Development of the overall breeding goal and selection index of Japanese Shorthorn using field records(Abstracts of the International Symposium on Recent Advances in Animal Science(IS-RAAS),Joint meeting of 2^<nd> IS-AS and 3^<rd> IS-IFS)
CANGAROO-III Search for Gamma Rays from SN 1987A and the Surrounding Field
Optical images of SN 1987A show a triple ring structure. The inner (dust)
ring has recently increased in brightness and in the number of hot spots
suggesting that the supernova shock wave has collided with the dense
pre-existing circumstellar medium, a scenario supported by radio and X-ray
observations. Such a shocked environment is widely expected to result in the
acceleration of charged particles, and the accompanying emission of very high
energy gamma-rays. Here, we report the results of observations made in 2004 and
2006 which yield upper limits on the TeV gamma-ray flux, which are compared
with a theoretical prediction. In addition, we set upper limits on the TeV flux
for four high energy objects which are located within the same field of view of
the observation: the super-bubble 30 Dor C, the Crab-like pulsar PSR
B054069, the X-ray binary LMC X-1, and the supernova remnant N157B.Comment: 5 pages, 5 figures, Accepted for publication in Ap
Observation of Very High Energy Gamma Rays from HESS J1804-216 with CANGAROO-III Telescopes
We observed the unidentified TeV gamma-ray source HESS J1804-216 with the
CANGAROO-III atmospheric Cerenkov telescopes from May to July in 2006. We
detected very high energy gamma rays above 600 GeV at the 10 sigma level in an
effective exposure of 76 hr. We obtained a differential flux of
(5.0+/-1.5_{stat}+/-1.6_{sys})\times 10^{-12}(E/1 TeV)^{-\alpha}
cm^{-2}s^{-1}TeV^{-1} with a photon index \alpha of 2.69 +/- 0.30_{stat} +/-
0.34_{sys}, which is consistent with that of the H.E.S.S. observation in 2004.
We also confirm the extended morphology of the source. By combining our result
with multi-wavelength observations, we discuss the possible counterparts of
HESS J1804-216 and the radiation mechanism based on leptonic and hadronic
processes for a supernova remnant and a pulsar wind nebula.Comment: 11 pages, 12 figures, Accepted in Ap
Phase and density dependence of the delayed annihilation of metastable antiprotonic helium atoms in gas, liquid and solid helium
Effects of impurity atoms and molecules on the lifetime of antiprotonic helium atoms
Delayed annihilation time spectra of antiprotons (DATS) in room temperature helium gas have been studied as a function of the concentration of admixed noble gases (Ne, Ar, Kr, Xe) as well as molecular gases (N_2,O_2,H_2) at the low energy antiproton ring (LEAR) at CERN. The DATS were a superposition of two exponential components, one with lifetime of several 100 ns and the other with lifetime 1 to 3 \mus. They showed a shorter average lifetime (T_{av}) than DATS of pure helium. Ne, Ar, and Kr were found to affect T_{av} only slightly even in concentrations up to 20\%, while Xe showed a much stronger influence. In the case of molecular gases the presence of N_2 influenced the DATS much less than O_2 and H_2 which destroyed the metastability almost completely in concentrations of 100 ppm and less. The decay rate of the slow component of DATS was found to exhibit a linear relation to the number density of the admixture. From this a collisional destruction (``quenching'') cross section \sigma_q was extracted. No evidence for a delayed annihilation of antiprotons in pure Ne, Kr, and Xe was observed
CANGAROO-III search for TeV Gamma-rays from two clusters of galaxies
Because accretion and merger shocks in clusters of galaxies may accelerate
particles to high energies, clusters are candidate sites for the origin of
ultra-high-energy (UHE) cosmic-rays. A prediction was presented for gamma-ray
emission from a cluster of galaxies at a detectable level with the current
generation of imaging atmospheric Cherenkov telescopes. The gamma-ray emission
was produced via inverse Compton upscattering of cosmic microwave background
(CMB) photons by electron-positron pairs generated by collisions of UHE cosmic
rays in the cluster. We observed two clusters of galaxies, Abell 3667 and Abell
4038, searching for very-high-energy gamma-ray emission with the CANGAROO-III
atmospheric Cherenkov telescope system in 2006. The analysis showed no
significant excess around these clusters, yielding upper limits on the
gamma-ray emission. From a comparison of the upper limit for the north-west
radio relic region of Abell 3667 with a model prediction, we derive a lower
limit for the magnetic field of the region of ~0.1 micro G. This shows the
potential of gamma-ray observations in studies of the cluster environment. We
also discuss the flux upper limit from cluster center regions using a model of
gamma-ray emission from neutral pions produced in hadronic collisions of
cosmic-ray protons with the intra-cluster medium (ICM). The derived upper limit
of the cosmic-ray energy density within this framework is an order of magnitude
higher than that of our Galaxy.Comment: 7 pages, 6 figures, Accepted in Ap
Observation of an extended VHE gamma-ray emission from MSH 15-52 with CANGAROO-III
We have observed the supernova remnant MSH 15-52 (G320.4-1.2), which contains
the gamma-ray pulsar PSR B1509-58, using the CANGAROO-III imaging atmospheric
Cherenkov telescope array from April to June in 2006. We detected gamma rays
above 810 GeV at the 7 sigma level during a total effective exposure of 48.4
hours. We obtained a differential gamma-ray flux at 2.35 TeV of
(7.9+/-1.5_{stat}+/-1.7_{sys}) \times 10^{-13} cm^{-2}s^{-1}TeV^{-1} with a
photon index of 2.21+/-0.39_{stat}+/-0.40_{sys}, which is compatible with that
of the H.E.S.S. observation in 2004. The morphology shows extended emission
compared to our Point Spread Function. We consider the plausible origin of the
high energy emission based on a multi-wavelength spectral analysis and
energetics arguments.Comment: 9 pages, 9 figures, Accepted in Ap
CANGAROO-III Observations of the supernova remnant RX J0852.04622
Sub-TeV gamma-ray emission from the North-West rim of the supernova remnant
RX J0852.04622 was detected with the CANGAROO-II telescope and recently
confirmed by the H.E.S.S. group. In addition, the H.E.S.S. data revealed a very
wide (up to two degrees in diameter), shell-like profile of the gamma-ray
emission. We have carried out CANGAROO-III observations in January and February
2005 with three telescopes and show here the results of three-fold coincidence
data. We confirm the H.E.S.S. results about the morphology and the energy
spectrum, and find the energy spectrum in the NW-rim is consistent with that of
the whole remnant.Comment: 9 pages, 13 figures, to appear in Ap
CANGAROO-III Search for Gamma Rays from Centaurus A and the Centauri Region
We have observed the giant radio galaxy Centaurus A and the globular cluster
Centauri in the TeV energy region using the CANGAROO-III stereoscopic
system. The system has been in operation since 2004 withan array of four
Imaging Atmospheric Cherenkov Telescopes (IACT) with 100-m spacings. The
observations were carried out in March and April 2004. In total, approximately
10 hours data were obtained for each target.No statistically significant
gamma-ray signal has been found above 420 GeV over a wide angular region (a
one-degree radius from thepointing center) and we derive flux upper limits
using all of the field of view.Implications for the total energy of cosmic rays
and the density of the cold dark matter are considered.Comment: 7 pages, 6 figures, to appear in ApJ, emulateapj.cl
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