498 research outputs found
A World of Fields
Trope ontology is exposed and confronted with the question where one trope ends and another begins. It is argued that tropes do not have determinate boundaries, it is arbitrary how tropes are carved up. An ontology, which I call field ontology, is proposed which takes this into account. The material world consists of a certain number of fields, each of which is extended over all of space. It is shown how field ontology can also tackle the problem of determin-able properties and the problem of completeness of things
Onset of collective and cohesive motion
We study the onset of collective motion, with and without cohesion, of groups
of noisy self-propelled particles interacting locally. We find that this phase
transition, in two space dimensions, is always discontinuous, including for the
minimal model of Vicsek et al. [Phys. Rev. Lett. {\bf 75},1226 (1995)] for
which a non-trivial critical point was previously advocated. We also show that
cohesion is always lost near onset, as a result of the interplay of density,
velocity, and shape fluctuations.Comment: accepted for publication in Phys. Rev. Let
Quasiparticle dynamics and in-plane anisotropy in system near onset of superconductivity
We report on an infrared study of carrier dynamics within the CuO
planes in heavily underdoped detwinned single crystals of YBaCuO. In an effort to reveal the electronic structure near the onset of
superconductivity, we investigate the strong anisotropy of the electromagnetic
response due to an enhancement of the scattering rate along the a-axis. We
propose that the origin of this anisotropy is related to a modulation of the
electron density within the CuO planes.Comment: 5 pages, 4 figure
First Spitzer Space Telescope Observations of Magnetic Cataclysmic Variables: Evidence for Excess Emission at 3--8 microns
We present the first observations of magnetic cataclysmic variables with the
Spitzer Space Telescope. We used the Infrared Array Camera to obtain photometry
of the polars EF Eri, GG Leo, V347 Pav, and RX J0154.0-5947 at 3.6, 4.5, 5.8,
and 8.0 m. In all of our targets, we detect excess mid-infrared emission
over that expected from the component stars alone. We explore the origin of
this IR excess by examining bremsstrahlung, cyclotron emission, circumbinary
dust, and L/T brown dwarf secondary stars. Bremsstrahlung and cyclotron
emission appear unlikely to be significant contributors to the observed fluxes.
At present, the most likely candidate for the excess emission is dust that is
probably located in a circumbinary disk with an inner temperature near 800 K.
However, a simple dust disk plus any reasonable low mass or brown dwarf-like
secondary star is unable to fully explain the observed flux densities in the
3--8 m region.Comment: Accepted to ApJ Letter
Разработка технических средств повышения эффективности солнечных установок
In this paper a method and means of increasing the power generated by solar installations during the day are considered. It is recommended to use acrylic concentrator and solar tracker with active type of tracking based on the control board without microcontrollers. This feature allows using DC commutator motor as an electric drive component, which simplifies the construction of the whole system significantly
First Evidence of -Dependence in the QCD Interquark Potential
We present a lattice calculation of the interquark potential between static
quarks in a ``full'' QCD simulation with 2 flavours of dynamical Wilson-quarks
at three intermediate sea-quark masses. We work at on lattice
size of with 100 configurations per sea-quark mass. We compare
the full QCD potential with its quenched counterpart at equal lattice spacing,
GeV, which is at the onset of the quenched scaling regime.
We find that the full QCD potential lies consistently below that of quenched
QCD. We see no evidence for string-breaking effects on these lattice volumes,
.Comment: 9 pages (1 tex file epsf-style + 6 ps-figures
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