15,098 research outputs found
The LSST Data Mining Research Agenda
We describe features of the LSST science database that are amenable to
scientific data mining, object classification, outlier identification, anomaly
detection, image quality assurance, and survey science validation. The data
mining research agenda includes: scalability (at petabytes scales) of existing
machine learning and data mining algorithms; development of grid-enabled
parallel data mining algorithms; designing a robust system for brokering
classifications from the LSST event pipeline (which may produce 10,000 or more
event alerts per night); multi-resolution methods for exploration of petascale
databases; indexing of multi-attribute multi-dimensional astronomical databases
(beyond spatial indexing) for rapid querying of petabyte databases; and more.Comment: 5 pages, Presented at the "Classification and Discovery in Large
Astronomical Surveys" meeting, Ringberg Castle, 14-17 October, 200
Electromagnetically Induced Transparency and Light Storage in an Atomic Mott Insulator
We experimentally demonstrate electromagnetically induced transparency and
light storage with ultracold 87Rb atoms in a Mott insulating state in a three
dimensional optical lattice. We have observed light storage times of about 240
ms, to our knowledge the longest ever achieved in ultracold atomic samples.
Using the differential light shift caused by a spatially inhomogeneous far
detuned light field we imprint a "phase gradient" across the atomic sample,
resulting in controlled angular redirection of the retrieved light pulse.Comment: 4 pages, 4 figure
Curriculum for Excellence Draft Experiences and Outcomes: Collection, analysis and reporting of data. Interim report.
Scotland, Catalonia and the ârightâ to self-determination: a comment suggested by Kathryn Crameriâs âDo Catalans Have the Right to Decide?
No abstract available
Hylleraas Variational Perturbation Theory: Application to Correlation Problems in Molecular Systems
Hylleraas variational perturbation theory is applied through second order in energy to estimate the correlation energy in several molecular systems. The specific choices for H0 and V which are made lead to equations nearly identical to the multireference linearized coupledâcluster method of Laidig and Bartlett. The results obtained are in virtually exact agreement where comparisons have been made. Results from test calculations are presented for BeH2, CH2, and C2H4. In addition, the utility of perturbation theory for selecting correlating configurations is examined. This procedure is found to be quite accurate while significantly reducing the size of the system of linear equations to be solved
KortewegâdeVries equation for longitudinal disturbances in coasting charged-particle beams
Ultrafast Plasmonic Control of Second Harmonic Generation
Efficient frequency conversion techniques are crucial to the development of
plasmonic metasurfaces for information processing and signal modulation. In
principle, nanoscale electric-field confinement in nonlinear materials enables
higher harmonic conversion efficiencies per unit volume than those attainable
in bulk materials. Here we demonstrate efficient second-harmonic generation
(SHG) in a serrated nanogap plasmonic geometry that generates steep electric
field gradients on a dielectric metasurface. An ultrafast pump is used to
control plasmon-induced electric fields in a thin-film material with inversion
symmetry that, without plasmonic enhancement, does not exhibit an an even-order
nonlinear optical response. The temporal evolution of the plasmonic near-field
is characterized with ~100as resolution using a novel nonlinear interferometric
technique. The ability to manipulate nonlinear signals in a metamaterial
geometry as demonstrated here is indispensable both to understanding the
ultrafast nonlinear response of nanoscale materials, and to producing active,
optically reconfigurable plasmonic device
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Were Presolar Grains Destroyed by the Nebular Process Responsible for the Volatile Element Fractionation?
We present SiC abundances from a number of CM and CR chondrites using NanoSIMS raster ion imaging of acid residues. We find higher SiC abundances for CRs than previously estimated based on noble gases
Gauged Dimension Bubbles
Some of the peculiar electrodynamical effects associated with gauged
``dimension bubbles'' are presented. Such bubbles, which effectively enclose a
region of 5d spacetime, can arise from a 5d theory with a compact extra
dimension. Bubbles with thin domain walls can be stabilized against total
collapse by the entrapment of light charged scalar bosons inside the bubble,
extending the idea of a neutral dimension bubble to accommodate the case of a
gauged U(1) symmetry. Using a dielectric approach to the 4d dilaton-Maxwell
theory, it is seen that the bubble wall is almost totally opaque to photons,
leading to a new stabilization mechanism due to trapped photons. Photon
dominated bubbles very slowly shrink, resulting in a temperature increase
inside the bubble. At some critical temperature, however, these bubbles
explode, with a release of radiation.Comment: 14 pages, no figures; to appear in Phys.Rev.
Geodetic Brane Gravity
Within the framework of geodetic brane gravity, the Universe is described as
a 4-dimensional extended object evolving geodetically in a higher dimensional
flat background. In this paper, by introducing a new pair of canonical fields
{lambda, P_{lambda}}, we derive the quadratic Hamiltonian for such a brane
Universe; the inclusion of matter then resembles minimal coupling. Second class
constraints enter the game, invoking the Dirac bracket formalism. The algebra
of the first class constraints is calculated, and the BRST generator of the
brane Universe turns out to be rank-1. At the quantum level, the road is open
for canonical and/or functional integral quantization. The main advantages of
geodetic brane gravity are: (i) It introduces an intrinsic, geometrically
originated, 'dark matter' component, (ii) It offers, owing to the Lorentzian
bulk time coordinate, a novel solution to the 'problem of time', and (iii) It
enables calculation of meaningful probabilities within quantum cosmology
without any auxiliary scalar field. Intriguingly, the general relativity limit
is associated with lambda being a vanishing (degenerate) eigenvalue.Comment: 23 pages, 1 figure, minor change
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