7,828 research outputs found
The 2D Euler-Poisson System with Spherical Symmetry
This article concerns the global-in-time existence of smooth solutions with
small amplitude to two space dimensional Euler-Poisson system. The main
difficulty lies in the slow time decay of the linear system.
Inspired by Ozawa, Tsutaya, and Tsutsumi's work, we show that such smooth
solutions exist for radially symmetric flows
Two-slit diffraction with highly charged particles: Niels Bohr's consistency argument that the electromagnetic field must be quantized
We analyze Niels Bohr's proposed two-slit interference experiment with highly
charged particles that argues that the consistency of elementary quantum
mechanics requires that the electromagnetic field must be quantized. In the
experiment a particle's path through the slits is determined by measuring the
Coulomb field that it produces at large distances; under these conditions the
interference pattern must be suppressed. The key is that as the particle's
trajectory is bent in diffraction by the slits it must radiate and the
radiation must carry away phase information. Thus the radiation field must be a
quantized dynamical degree of freedom. On the other hand, if one similarly
tries to determine the path of a massive particle through an inferometer by
measuring the Newtonian gravitational potential the particle produces, the
interference pattern would have to be finer than the Planck length and thus
undiscernable. Unlike for the electromagnetic field, Bohr's argument does not
imply that the gravitational field must be quantized.Comment: 8 pages, 4 figures. To appear in Proc. Natl. Acad. Sc
Portable reflectance spectrometer
A portable reflectance spectrometer is disclosed. The spectrometer essentially includes an optical unit and an electronic recording unit. The optical unit includes a pair of thermoelectrically-cooled detectors, for detecting total radiance and selected radiance projected through a circular variable filter wheel, and is capable of operating to provide spectral data in the range 0.4 to 2.5 micrometers without requiring coventional substitution of filter elements. The electronic recording unit includes power supplies, amplifiers, and digital recording electronics designed to permit recordation of data on tape casettes. Both the optical unit and electronic recording unit are packaged to be manually portable
Conservation laws, uncertainty relations, and quantum limits of measurements
The uncertainty relation between the noise operator and the conserved
quantity leads to a bound for the accuracy of general measurements. The bound
extends the assertion by Wigner, Araki, and Yanase that conservation laws limit
the accuracy of ``repeatable'', or ``nondisturbing'', measurements to general
measurements, and improves the one previously obtained by Yanase for spin
measurements. The bound also sets an obstacle to making a small quantum
computer.Comment: 4 pages, RevTex, to appear in PR
Larval ontogeny of a percichthyid fish, Synagrops philippinensis (GĂŒnther) in Kagoshima Bay, southern Japan
The larval ontogeny of a developmental series (1.2-8.3mm body length, BL) of Synagrops philippinensis from Kagoshima Bay, southern Japan is described and illustrated. The yolk was completely absorbed in larva of â„1.5 mm BL. Notochord flexion commenced at about 3.5mm BL and was completed by about 4.0-4.5mm BL. S. philippinensis larvae were distinguished from their congeners based on melanophore patterns, head spination and fin spines and rays. Larvae of 7.5-8.3 mm BL were characterized by anteriorly serrated pelvic spine, two anal spines, nine inner preopercular spines and no melanophore on lateral side of the caudal peduncle; 7.0 to 7.5mm BL larvae by the above characters except serration on pelvic spine; and yolk-sac, pre-flexion, flexing and post-flexion larvae up to 7.0mm BL by unique melanophores on lower lobe of pectoral finfold/fin
Global solutions in the critical Sobolev space for the wave equations with nonlinearity of exponential growth
LECTURES ON NONLINEAR DISPERSIVE EQUATIONS II
Program
N. Tzvetkov
Ill-posedness issues for nonlinear dispersive equations
H. Koch
Dispersive estimates and application
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