3,978 research outputs found
A size criterion for macroscopic superposition states
An operational measure to quantify the sizes of some ``macroscopic quantum
superpositions'', realized in recent experiments, is proposed. The measure is
based on the fact that a superposition presents greater sensitivity in
interferometric applications than its superposed constituent states. This
enhanced sensitivity, or ``interference utility'', may then be used as a size
criterion among superpositions.Comment: LaTeX2e-REVTeX4, 9 pages, 3 figures. V2: introduction and discussion
slightly altere
Paired composite fermion phase of quantum Hall bilayers at \nu = 1/2 + 1/2
We provide numerical evidence for composite fermion pairing in quantum Hall
bilayer systems at filling for intermediate spacing between the
layers. We identify the phase as pairing, and construct high
accuracy trial wavefunctions to describe the groundstate on the sphere. For
large distances between the layers, and for finite systems, a competing "Hund's
rule" state, or composite fermion liquid, prevails for certain system sizes. We
argue that for larger systems, the pairing phase will persist to larger layer
spacing.Comment: 4 pages, 2 figures; v2: final version, as published in journa
Time-dependent magnetotransport of a wave packet in a quantum wire with embedded quantum dots
We consider wave packet propagation in a quantum wire with either an embedded
antidot or an embedded parallel double open quantum dot under the influence of
a uniform magnetic field. The magnetoconductance and the time evolution of an
electron wave packet are calculated based on the Lippmann-Schwinger formalism.
This approach allows us to look at arbitrary embedded potential profiles and
illustrate the results by performing computational simulations for the
conductance and the time evolution of the electron wave packet through the
quantum wire. In the double-dot system we observe a long-lived resonance state
that enhances the spatial spreading of the wave packet, and quantum
skipping-like trajectories are induced when the envelop function of the wave
packet covers several subbands in appropriate magnetic fields.Comment: RevTeX, 9 pages with 8 included postscript figure
Borel Degenerations of Arithmetically Cohen-Macaulay curves in P^3
We investigate Borel ideals on the Hilbert scheme components of
arithmetically Cohen-Macaulay (ACM) codimension two schemes in P^n. We give a
basic necessary criterion for a Borel ideal to be on such a component. Then
considering ACM curves in P^3 on a quadric we compute in several examples all
the Borel ideals on their Hilbert scheme component. Based on this we conjecture
which Borel ideals are on such a component, and for a range of Borel ideals we
prove that they are on the component.Comment: 20 pages, shorter and more effective versio
Avalanche defences for Flateyri, Iceland. From hazard evaluation to construction of defences.
The village of Flateyri was hit by two major avalanches in 1995, with the latter one killing 20 of the 45 people caught in it. These, together with the catastrophic avalanche in the nearby SúôavĂk in January the same year, initiated a complete review of all government actions and regulations regarding avalanche risk and avalanche defences in Iceland. The government set a long term goal for the acceptable risk to people living in avalanche prone areas and increased funding for the construction of avalanche defences. The avalanche situation in Flateyri is quite serious and the risk the inhabitants live with is very high. The town is threatened by avalanches from two gullies, Innra-Bæjargil in the north-west and Skollahvilft in the north-east, with several records of avalanches reaching well into the present residential area. To fulfil the safety requirements, an appraisal study was carried out and a proposal made for avalanche defences for the community, consisting of two earthfill deflecting dams and an earthfill catching dam. The proposal was accepted by the local authorities and the Icelandic government in the spring of 1996, design work was carried out in that summer and construction work started in September 1996. The construction of the dams is now close to completion, two years after the accident
Characterization of Particulate Matter Accumulated on Ramalina farinacea in the Seattle Area Using Semi-Automated Electron Microscopy
Semi-automated scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDS) can be used to determine the size and composition of filtered particulate matter (PM). This information is valuable for determining the identity and contribution of overlapping air emissions. One limitation of this method is the cost of filtering PM at enough locations to give meaningful spatial data. To address this limitation, I developed an exploratory method to collect PM using Ramalina farinacea for semi-automated SEM analysis as a component of lichen biomonitoring studies. I applied this method as a proof of concept in the Seattle area to better understand trends in regional urban dust. To do this, bags of lichen were transplanted to 9 locations in the Duwamish Valley and adjacent uplands for 3 months between September and December, 2017. Some of these locations were arranged close to major industrial sources of airborne metals, which we hypothesized would contribute to the PM observed on the lichens alongside the regional background signature of particulate emissions. Upon collection, PM deposition on the lichen was characterized using SEM with EDS. A total of 18,581 particles were identified and analyzed using the PACLA for Oxford two-stage classifier. My findings suggest that R. farinacea are an effective tool for collecting PM and show the greatest proportion of anthropogenic-specific particles on lichens adjacent to Interstate 5. Furthermore, the spatial trends of PM between locations suggest that fugitive dust controls such as green walls and green spaces may be more effective than point source controls at further reducing exposure to harmful dust in the Seattle area
Entanglement quantification through local observable correlations
We present a significantly improved scheme of entanglement detection inspired
by local uncertainty relations for a system consisting of two qubits.
Developing the underlying idea of local uncertainty relations, namely
correlations, we demonstrate that it's possible to define a measure which is
invariant under local unitary transformations and which is based only on local
measurements. It is quite simple to implement experimentally and it allows
entanglement quantification in a certain range for mixed states and exactly for
pure states, without first obtaining full knowledge (e.g. through tomography)
of the state.Comment: 5 pages, 3 figures, revised version with new proof and replaced
figure
Economic study of the range cattle industry in Colorado
May 9, 1925.Includes bibliographical references (pages 264-297)
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