546 research outputs found
Scenario for Fractional Quantum Hall Effect in Bulk Isotropic Materials
We investigate the possibility of a strongly correlated Fractional Quantum
Hall (FQH) state in bulk three dimensional isotropic (not layered) materials.
We find that a FQH state can exist at low densities only if it is accompanied
by a staging transition in which the electrons re-organize themselves in
layers, perpendicular to the magnetic field, at distances of order the magnetic
length apart. The Hartree energy associated to the staging transition is
off-set by the correlation Fock energy of the 3D FQH state. We obtain the phase
diagram of bulk electrons in a magnetic field subject to Coulomb interactions
as a function of carrier density and lattice constant. At very low densities,
the 3D FQH state exhibits a transition to a 3D Wigner crystal state stabilized
by phonon correlations
Monopole Flux State on the Pyrochlore Lattice
The ground state of a spin 1/2 nearest neighbor quantum Heisenberg
antiferromagnet on the pyrochlore lattice is investigated using a large
SU(N) fermionic mean field theory. We find several mean field states, of which
the state of lowest energy upon Gutzwiller projection, is a parity and time
reversal breaking chiral phase with a unit monopole flux exiting each
tetrahedron. This "monopole flux" state has a Fermi surface consisting of 4
lines intersecting at a point. At mean field the low-energy excitations about
the Fermi surface are gapless spinons. An analysis using the projective
symmetry group of this state suggests that the state is stable to small
fluctuations which neither induce a gap, nor alter the unusual Fermi surface
Earth Observations Division version of the Laboratory for Applications of Remote Sensing System (EOD-LARSYS) user guide for the IBM 370/148. Volume 3: As-built documentation (sections 13-23)
There are no author-identified significant results in this report
Earth Observations Division version of the Laboratory for Applications of Remote Sensing system (EOD-LARSYS) user guide for the IBM 370/148. Volume 4: Program listings
There are no author-identified significant results in this report
Excess sub-millimetre emission from GRS 1915+105
We present the first detections of the black hole X-ray binary GRS 1915+105
at sub-millimetre wavelengths. We clearly detect the source at 350 GHz on two
epochs, with significant variability over the 24 hr between epochs.
Quasi-simultaneous radio monitoring indicates an approximately flat spectrum
from 2 - 350 GHz, although there is marginal evidence for a minimum in the
spectrum between 15 - 350 GHz. The flat spectrum and correlated variability
imply that the sub-mm emission arises from the same synchrotron source as the
radio emission. This source is likely to be a quasi-steady partially
self-absorbed jet, in which case these sub-mm observations probe significantly
closer to the base of the jet than do radio observations and may be used in
future as a valuable diagnostic of the disc:jet connection in this source.Comment: 5 pages, 3 figures, accepted for publication in MNRA
Aquaculture and its role in integrated coastal zone management: handbook of contributions and extended abstracts presented at the International Workshop on "Aquaculture and its role in Integrated Coastal Zone Management" Oostende, Belgium, April 19-21, 2001
Legislative strengthening meets party support in international assistance: a closer relationship?
Recent reports recommend that international efforts to help strengthen legislatures in emerging democracies should work more closely with support for building stronger political parties and competitive party systems. This article locates the recommendations within international assistance more generally and reviews the arguments. It explores problems that must be addressed if the recommendations are to be implemented effectively. The article argues that an alternative, issue-based approach to strengthening legislatures and closer links with civil society could gain more traction. However, that is directed more centrally at promoting good governance for the purpose of furthering development than at democratisation goals sought by party aid and legislative strengtheners in the democracy assistance industry
Normal state properties of high angle grain boundaries in (Y,Ca)Ba2Cu3O7-delta
By lithographically fabricating an optimised Wheatstone bridge geometry, we
have been able to make accurate measurements of the resistance of grain
boundaries in Y1-xCaxBa2Cu3O7-d between the superconducting transition
temperature, Tc, and room temperature. Below Tc the normal state properties
were assessed by applying sufficiently high currents. The behaviour of the
grain boundary resistance versus temperature and of the conductance versus
voltage are discussed in the framework charge transport through a tunnel
barrier. The influence of misorientation angle, oxygen content, and calcium
doping on the normal state properties is related to changes of the height and
shape of the grain boundary potential barrier.Comment: 17 pages, 1 table, 5 figures, submitted to PR
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