59,834 research outputs found
Correlation of the earth's rotation rate and the secular change of the geomagnetic field
Power spectral density analysis using Burg's maximum entropy method was applied to the geomagnetic dipole field and its rate of change for the years 1901 to 1969. Both spectra indicate relative maxima at 0.015 cycles/year and its harmonics. These maxima correspond approximately to 66, 33, 22, 17, 13, 11, and 9-year spectral lines. The application of the same analysis techniques to the length-of-day (l.o.d) fluctuations for the period 1865 to 1961 reveal similar spectral characteristics. Although peaks were observed at higher harmonics of the fundamental frequency, the 22-year and 11-year lines are not attributed unambiguously to the solar magnetic cycle and the solar cycle. It is suggested that the similarity in the l.o.d fluctuations and the dipole field variations is related to the motion within the earth's fluid core during the past one hundred years
Temperature Dependence of the Magnetic Penetration Depth in the Vortex State of the Pyrochlore Superconductor, Cd2Re2O7
We report transverse field and zero field muon spin rotation studies of the
superconducting rhenium oxide pyrochlore, Cd2Re2O7. Transverse field
measurements (H=0.007 T) show line broadening below Tc, which is characteristic
of a vortex state, demonstrating conclusively the type-II nature of this
superconductor. The penetration depth is seen to level off below about 400 mK
(T/Tc~0.4), with a rather large value of lambda (T=0)~7500A. The temperature
independent behavior below ~ 400 mK is consistent with a nodeless
superconducting energy gap. Zero-field measurements indicate no static magnetic
fields developing below the transition temperature.Comment: 4 pages, 4 figures, REVTEX 4, submitted to PR
Changes in the measured image separation of the gravitational lens system, PKS 1830-211
We present eight epochs of 43 GHz, dual-polarisation VLBA observations of the
gravitational lens system PKS 1830-211, made over fourteen weeks. A bright,
compact ``core'' and a faint extended ``jet'' are clearly seen in maps of both
lensed images at all eight epochs.
The relative separation of the radio centroid of the cores (as measured on
the sky) changes by up to 87 micro arcsec between subsequent epochs.
A comparison with the previous 43 GHz VLBA observations (Garrett et al. 1997)
made 8 months earlier show even larger deviations in the separation of up to
201 micro arcsec. The measured changes are most likely produced by changes in
the brightness distribution of the background source, enhanced by the
magnification of the lens. A relative magnification matrix that is applicable
on the milliarcsecond scale has been determined by relating two vectors (the
``core-jet'' separations and the offsets of the polarised and total intensity
emission) in the two lensed images. The determinant of this matrix,
-1.13 +/-0.61, is in good agreement with the measured flux density ratio of
the two images. The matrix predicts that the 10 mas long jet, that is clearly
seen in previous 15 and 8.4 GHz VLBA observations (Garrett et al. 1997,
Guirado et al. 1999), should correspond to a 4 mas long jet trailing to the
south-east of the SW image. The clear non-detection of this trailing jet is a
strong evidence for sub-structure in the lens and may require more realistic
lens models to be invoked, e.g. Nair & Garrett (2000).Comment: 8 pages, 5 figure
Thermodynamics of lattice QCD with 2 flavours of colour-sextet quarks: A model of walking/conformal Technicolor
QCD with two flavours of massless colour-sextet quarks is considered as a
model for conformal/walking Technicolor. If this theory possess an infrared
fixed point, as indicated by 2-loop perturbation theory, it is a
conformal(unparticle) field theory. If, on the other hand, a chiral condensate
forms on the weak-coupling side of this would-be fixed point, the theory
remains confining. The only difference between such a theory and regular QCD is
that there is a range of momentum scales over which the coupling constant runs
very slowly (walks). In this first analysis, we simulate the lattice version of
QCD with two flavours of staggered quarks at finite temperatures on lattices of
temporal extent and 6. The deconfinement and chiral-symmetry
restoration couplings give us a measure of the scales associated with
confinement and chiral-symmetry breaking. We find that, in contrast to what is
seen with fundamental quarks, these transition couplings are very different.
for each of these transitions increases significantly from
and as expected for the finite temperature transitions of an
asymptotically-free theory. This suggests a walking rather than a conformal
behaviour, in contrast to what is observed with Wilson quarks. In contrast to
what is found for fundamental quarks, the deconfined phase exhibits states in
which the Polyakov loop is oriented in the directions of all three cube roots
of unity. At very weak coupling the states with complex Polyakov loops undergo
a transition to a state with a real, negative Polyakov loop.Comment: 21 pages, 9 figures, Revtex with postscript figures. One extra
reference was added; text is unchanged. Corrected typographical erro
Recent Experiments with Bose-Condensed Gases at JILA
We consider a binary mixture of two overlapping Bose-Einstein condensates in
two different hyperfine states of \Rb87 with nearly identical magnetic moments.
Such a system has been simply realized through application of radiofrequency
and microwave radiation which drives a two-photon transition between the two
states. The nearly identical magnetic moments afford a high degree of spatial
overlap, permitting a variety of new experiments. We discuss some of the
conditions under which the magnetic moments are identical, with particular
emphasis placed on the requirements for a time-averaged orbiting potential
(TOP) magnetic trap.Comment: 9 pages, 5 figures; corrected post-publication editio
Pulsars in FIRST Observations
We identified 16 pulsars from the Faint Images of the Radio Sky at Twenty-cm
(FIRST) at 1.4 GHz. Their positions and total flux densities are extracted from
the FIRST catalog. Comparing the source positions with those in the PSRcatalog,
we obtained better determined positions of PSRs J1022+1001, J1518+4904,
J1652+2651, and proper motion upper limits of another three pulsars PSRs
J0751+1807, J1012+5307, J1640+2224. Proper motions of the other 10 pulsars are
consistent with the values in the catalog.Comment: 6 pages, 2 figures, 3 tables, submited to CJA
ECONOMIC IMPACTS OF CALIFORNIA'S GOLF COURSE FACILITIES IN 2000
People spent 7.872 billion, 1.370 billion in 2000. Direct sales of $4.251 billion directly supported 62,173 jobs, and , through indirect and induced sales impacts, an additional 37,609 jobs.Land Economics/Use,
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