29,585 research outputs found
Spinon Phonon Interaction and Ultrasonic Attenuation in Quantum Spin Liquids
Several experimental candidates for quantum spin liquids have been discovered
in the past few years which appear to support gapless fermionic excitations called spinons. The spinons may form a Fermi sea coupled to a
gauge field, and may undergo a pairing instability. We show that despite
being charge neutral, the spinons couple to phonons in exactly the same way
that electrons do in the long wavelength limit. Therefore we can use sound
attenuation to measure the spinon mass and lifetime. Furthermore, transverse
ultrasonic attenuation is a direct probe of the onset of pairing because the
Meissner effect of the gauge field causes a "rapid fall" of the attenuation at
in addition to the reduction due to the opening of the energy gap. This
phenomenon, well known in clean superconductors, may reveal the existence of
the U(1) gauge field.Comment: 4+epsilon pages of main text + 12 pages of supplementary materia
Automatic rendezvous system testing at the Flight Robotics Laboratory
The Flight Robotics Laboratory of MSFC provides sophisticated real time simulation capability in the study of human/system interactions of remote systems. This paper will describe the Flight Robotics Facility of NASA/MSFC, the hardware-in-the-loop simulation configuration, and test results
Ocean shrimp report 1979 season
Statewide Pacific ocean shrimp, Pandalus jordani, landings
totaled 2,237.7 mt (4,922,857 lb), down 3,745 mt
(8,240,386 lb) from the 1978 catch of 5,983.3 mt
(13,163,243 lb). The 1979 landings are the lowest
since 1976 when 1,545.5 mt (3,400,191 lb) were landed. Area A (Eureka-Crescent City)landings dropped to 1,842.5 mt (4,053,605 lb) from 5,046.3 mt (11,101,895 lb) landed during the previous season. No landings were made in Area B-1 (Fort Bragg). Only 2.0 mt (4,385 lb) were reported caught in Area B-2 (Bodega Bay). Record landings of 393.1 mt
(864,867 lb) were made in Area C (Morro Bay-Avila), surpassing the previous record of 90.4 mt (199,000 lb) landed in 1953. In Area A a record 71 vessels, 34 double-rigged and 37 single-rigged, shrimped during the
season. Average catch per hour was a low .15 mt (338 lb) and .22 mt (490 1b) for single-rig and double-rig vessels, respectively. In Area C average catch per hour was .23 mt (508 lb) and .42 mt (924 lb) for single-rig and double-rig
vessels, respectively. Area A shrimp catches were dominated by 1-year-old shrimp throughout most of the season. The
age composition in Area C shifted predominately from 2-year-old shrimp in May and June to predominately 1-year-old shrimp in July, August, October, and November. Area A was closed for one month from July 15 to
August 15 because closure criteria of less than .16 mt
(350 lb) per hour for two consecutive weeks was met and year class composition exceeded 70% of 1-year-old shrimp. The season was closed October 14 when the catch per hour criterion was exceeded again. (18pp.
KUV 01584-0939: A Helium-transferring Cataclysmic Variable with an Orbital Period of 10 Minutes
High speed photometry of KUV 01584-0939 (alias Cet3) shows that is has a
period of 620.26 s. Combined with its hydrogen-deficient spectrum, this implies
that it is an AM CVn star. The optical modulation is probably a superhump, in
which case the orbital period will be slightly shorter than what we have
observed.Comment: Published by PASP. See also the latest Early-Release Research Paper
website of the PAS
A Variational Monte Carlo Study of the Current Carried by a Quasiparticle
With the use of Gutzwiller-projected variational states, we study the
renormalization of the current carried by the quasiparticles in
high-temperature superconductors and of the quasiparticle spectral weight. The
renormalization coefficients are computed by the variational Monte Carlo
technique, under the assumption that quasiparticle excitations may be described
by Gutzwiller-projected BCS quasiparticles. We find that the current
renormalization coefficient decreases with decreasing doping and tends to zero
at zero doping. The quasiparticle spectral weight Z_+ for adding an electron
shows an interesting structure in k space, which corresponds to a depression of
the occupation number k just outside the Fermi surface. The perturbative
corrections to those quantities in the Hubbard model are also discussed.Comment: 9 pages, 9 figure
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