9,853 research outputs found
Microwave ISM Emission Observed by WMAP
We investigate the nature of the diffuse Galactic emission in the Wilkinson
Microwave Anisotropy Probe (WMAP) temperature anisotropy data. Substantial
dust-correlated emission is observed at all WMAP frequencies, far exceeding the
expected thermal dust emission in the lowest frequency channels (23, 33, 41
GHz). The WMAP team (Bennett et al.) interpret this emission as dust-correlated
synchrotron radiation, attributing the correlation to the natural association
of relativistic electrons produced by SNae with massive star formation in dusty
clouds, and deriving an upper limit of 5% on the contribution of Draine &
Lazarian spinning dust at K-band (23 GHz). We pursue an alternative
interpretation that much, perhaps most, of the dust-correlated emission at
these frequencies is indeed spinning dust, and explore the spectral dependence
on environment by considering a few specific objects as well as the full sky
average. Models similar to Draine & Lazarian spinning dust provide a good fit
to the full-sky data. The full-sky fit also requires a significant component
with free-free spectrum uncorrelated with \Halpha, possibly hot (~million K)
gas within 30 degrees of the Galactic center.Comment: ApJ in press (accepted 5 Dec 2003), version 2: corrected typos and
added references. 23 pages, 5 figures, 2 tables. Free-free haze map is
available at http://skymaps.inf
Discovery of a high-redshift Einstein ring
We report the discovery of a partial Einstein ring of radius 1.48arcsec
produced by a massive (and seemingly isolated) elliptical galaxy. The
spectroscopic follow-up at the VLT reveals a 2L* galaxy at z=0.986, which is
lensing a post-starburst galaxy at z=3.773. This unique configuration yields a
very precise measure of the mass of the lens within the Einstein radius,
(8.3e11 +- 0.4)/h70 Msolar. The fundamental plane relation indicates an
evolution rate of d [log (M/L)B] / dz = -0.57+-0.04, similar to other massive
ellipticals at this redshift. The source galaxy shows strong interstellar
absorption lines indicative of large gas-phase metallicities, with fading
stellar populations after a burst. Higher resolution spectra and imaging will
allow the detailed study of an unbiased representative of the galaxy population
when the universe was just 12% of its current age.Comment: 5 pages, 3 figures, accepted in A&A Le
Hydrodynamics of superfluids confined in blocked rings and wedges
Motivated by many recent experimental studies of non-classical rotational
inertia (NCRI) in superfluid and supersolid samples, we present a study of the
hydrodynamics of a superfluid confined in the two-dimensional region
(equivalent to a long cylinder) between two concentric arcs of radii and
() subtending an angle , with . The case
corresponds to a blocked ring. We discuss the methodology to
compute the NCRI effects, and calculate these effects both for small angular
velocities, when no vortices are present, and in the presence of a vortex. We
find that, for a blocked ring, the NCRI effect is small, and that therefore
there will be a large discontinuity in the moment of inertia associated with
blocking or unblocking circular paths. For blocked wedges () with , we find an unexpected divergence of the velocity at the origin, which
implies the presence of either a region of normal fluid or a vortex for {\it
any} nonzero value of the angular velocity. Implications of our results for
experiments on "supersolid" behavior in solid are discussed. A
number of mathematical issues are pointed out and resolved.Comment: 15 pages, including figures. To appear in Phys. Rev.
Melting and structure of the vortex solid in strongly anisotropic layered superconductors with random columnar pins
We study the melting transition of the low-temperature vortex solid in
strongly anisotropic layered superconductors with a concentration of random
columnar pinning centers small enough so that the areal density of the pins is
much less than that of the vortex lines. Both the external magnetic field and
the columnar pins are assumed to be oriented perpendicular to the layers Our
method, involving numerical minimization of a model free energy functional,
yields not only the free energy values at the local minima of the functional
but also the detailed density distribution of the system at each minimum: this
allows us to study in detail the structure of the different phases. We find
that at these pin concentrations and low temperatures, the thermodynamically
stable state is a topologically ordered Bragg glass. This nearly crystalline
state melts into an interstitial liquid (a liquid in which a small fraction of
vortex lines remain localized at the pinning centers) in two steps, so that the
Bragg glass and the liquid are separated by a narrow phase that we identify
from analysis of its density structure as a polycrystalline Bose glass. Both
the Bragg glass to Bose glass and the Bose glass to interstitial liquid
transitions are first-order. We also find that a local melting temperature
defined using a criterion based on the degree of localization of the vortex
lines exhibits spatial variations similar to those observed in recent
experiments.Comment: 17 page
Conceptual design of the EU-DEMO dual coolant lithium lead equatorial module
© 20xx IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.Within the framework of EUROfusion Program, the Dual Coolant Lithium Lead (DCLL) is one of the four EU breeder blanket concepts that are being investigated as candidates for DEMO. DCLL uses PbLi as the main coolant, tritium breeder, tritium carrier, and neutron multiplier. The main structures, including the first wall, are cooled with helium. The EU program proposed for the next years will consider a DCLL version limited to 550 °C in order to allow the use of conventional materials and technologies. During the first year of EUROfusion activities, a draft design of the DCLL has been proposed. The main blanket performances were adapted to the new specifications and the CAD model of DEMO. The breeder zone has been toroidally divided into four parallel PbLi circuits, separated through stiffening grid radial walls. The PbLi flow routing has been designed to maximize the amount of thermal power extracted by flowing PbLi and to avoid the occurrence of reverse flows due to volumetric heating. Thermal hydraulics, magnetohydrodynamic and neutronics calculations have been performed for the first draft design. The new DCLL design employs Eurofer-alumina-Eurofer sandwich as flow channel insert (FCI).Postprint (published version
On a conjecture on the integrability of Liénard systems
We consider the Liénard differential systems ̇x=y+F(x), ̇y=x (1), in C2 where F(x) is an analytic function satisfying F(0) = 0 and F'(0) ≠ 0. Then these systems have a strong saddle at the origin of coordinates. It has been conjecture that if such systems have an analytic first integral defined in a neighborhood of the origin, then the function F(x) is linear, i.e. F(x) = ax. Here we prove this conjecture, and show that when F(x) is linear and system (1) has an analytic first integral, this is a polynomial
A new species of Arachis (Fabaceae) from Mato Grosso, Brazil, related to Arachis Matiensis.
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