735 research outputs found
Passing through the `chiral limit' in quenched QCD with Wilson fermions
We investigate the limit of vanishing quark mass in quenched lattice QCD with
unimproved Wilson fermions at . Exploiting the correlations of
propagators at different time slices we extract pion masses extremely close to
the `chiral limit', despite the presence of `exceptional configurations'. With
this at hand, the existence of quenched chiral logarithms can be demonstrated,
provided, finite size effects are small. With reference to the phase diagram
proposed by Aoki also the range is investigated. The width
of a potential parity-flavor violating phase can, if at all, hardly be
resolved.Comment: LATTICE98(spectrum
Effects of spatial size, lattice doubling and source operator on the hadron spectrum with dynamical staggered quarks
We have extended our previous study of the lattice QCD spectrum with 2
flavors of staggered dynamical quarks at and and 0.01
to larger lattices, with better statistics and with additional sources for the
propagators. The additional sources allowed us to estimate the mass
and to measure the masses of all mesons whose operators are local in time.
These mesons show good evidence for flavor symmetry restoration, except for the
masses of the Goldstone and non-Goldstone pions. PCAC is observed in that
, and is estimated. Use of undoubled lattices
removes problems with the pion propagator found in our earlier work. Previously
we found a large change in the nucleon mass at a quark mass of when
we increased the spatial size from 12 to 16. No such effect is observed at the
larger quark mass, . Two kinds of wall source were used, and we
have found difficulties in getting consistent results for the nucleon mass
between the two sources.Comment: 30 pages PostScript fil
Hadron Spectrum in QCD with Valence Wilson Fermions and Dynamical Staggered Fermions at $6/g^2=5.6
We present an analysis of hadronic spectroscopy for Wilson valence quarks
with dynamical staggered fermions at lattice coupling at
sea quark mass and 0.025, and of Wilson valence quarks in quenched
approximation at and 5.95, both on lattices. We
make comparisons with our previous results with dynamical staggered fermions at
the same parameter values but on lattices doubled in the temporal
direction.Comment: 32 page
A numerical reinvestigation of the Aoki phase with N_f=2 Wilson fermions at zero temperature
We report on a numerical reinvestigation of the Aoki phase in lattice QCD
with two flavors of Wilson fermions where the parity-flavor symmetry is
spontaneously broken. For this purpose an explicitly symmetry-breaking source
term was added to the fermion action.
The order parameter was computed with
the Hybrid Monte Carlo algorithm at several values of on
lattices of sizes to and extrapolated to . The existence of a
parity-flavor breaking phase can be confirmed at and 4.3, while we
do not find parity-flavor breaking at and 5.0.Comment: 8 pages, 5 figures, Revised version as to be published in Phys.Rev.
Integrated Distributed Energy Resource Pricing and Control
U.S. policy is to allow owners of distributed resources to effectively and reliably provide their services at scale, and operate harmoniously on an interconnected distribution and transmission grid. Accordingly, regulation, new business models and technology advances over the past decade have led to significant growth rates in distributed energy resources including generation, responsive demand, energy conservation and customer adoption of industrial, commercial and residential energy management systems. The result is that several regions are reaching proposed capacity levels for distributed generation that exceed traditional operating and engineering practices for distribution systems. At the same time, policies advocating wholesale spot prices to customer devices (âprices to devicesâ) have not adequately considered distribution system reliability impacts or relationship to distributed generation. As such, it is also not clear that current market models or regulations are entirely adequate or appropriate for the several emerging hybrid regional markets, such as California, with millions of distributed energy resources envision by the year 2020
The pi-N Sigma term - an evaluation using staggered fermions
A lattice calculation of the pi-N sigma term is described using dynamical
staggered fermions. Preliminary results give a sea term comparable in magnitude
to the valence term.Comment: Latex article, 3 pages. Contribution to the LAT93 Conference (Dallas,
U.S.A., September 1993). HLRZ preprint 93-7
Properties of the a1 Meson from Lattice QCD
We determine the mass and decay constant of the meson using Monte Carlo
simulation of lattice QCD. We find MeV and , in good agreement with experiment.Comment: 9 page uu-encoded compressed postscript file. version appearing in
Phys. Rev. Lett. 74 (1995) 459
Simulation and observations of stratospheric aerosols from the 2009 Sarychev volcanic eruption
We used a general circulation model of Earthâs climate to conduct simulations of the 12-16 June 2009 eruption of Sarychev volcano (48.1°N, 153.2°E). The model simulates the formation and transport of the stratospheric sulfate aerosol cloud from the eruption and the resulting climate response. We compared optical depth results from these simulations with limb scatter measurements from the Optical Spectrograph and InfraRed Imaging System (OSIRIS), in situ measurements from balloon-borne instruments lofted from Laramie, Wyoming (41.3°N, 105.7°W), and five lidar stations located throughout the Northern Hemisphere. The aerosol cloud covered most of the Northern Hemisphere, extending slightly into the tropics, with peak backscatter measured between 12 and 16 km in altitude. Aerosol concentrations returned to near background levels by Spring, 2010. After accounting for expected sources of discrepancy between each of the data sources, the magnitudes and spatial distributions of aerosol optical depth due to the eruption largely agree. In conducting the simulations, we likely overestimated both particle size and the amount of SO2 injected into the stratosphere, resulting in modeled optical depth values that were a factor of 2-4 too high. Model results of optical depth due to the eruption show a peak too late in high latitudes and too early in low latitudes, suggesting a problem with stratospheric circulation in the model. The model also shows a higher annual decay rate in optical depth than is observed, showing an inaccuracy in seasonal deposition rates. The modeled deposition rate of sulfate aerosols from the Sarychev eruption is higher than the rate calculated for aerosols from the 1991 eruption of Mt. Pinatubo
SMOS-NEXT: A New Concept for Soil Moisture Retrieval from Passive Interferometric Observations
This book is a collection of 19 articles which reflect the courses given at the CollĂšge de France/Summer school âReconstruction d'images â Applications astrophysiquesâ held in Nice and FrĂ©jus, France, from June 18 to 22, 2012. The articles presented in this volume address emerging concepts and methods that are useful in the complex process of improving our knowledge of the celestial objects, including Earth
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