1,029 research outputs found
Light quark mass effects in the on-shell renormalization constants
We compute the three-loop relation between the pole and the minimally
subtracted quark mass allowing for virtual effects from a second massive quark.
We also consider the analogue effects for the on-shell wave function
renormalization constant.Comment: 24 page
Uncertainty in Signals of Large-Scale Climate Variations in Radiosonde and Satellite Upper-Air Temperature Datasets
There is no single reference dataset of long-term global upper-air temperature observations, although several
groups have developed datasets from radiosonde and satellite observations for climate-monitoring purposes. The
existence of multiple data products allows for exploration of the uncertainty in signals of climate variations and
change. This paper examines eight upper-air temperature datasets and quantifies the magnitude and uncertainty
of various climate signals, including stratospheric quasi-biennial oscillation (QBO) and tropospheric ENSO
signals, stratospheric warming following three major volcanic eruptions, the abrupt tropospheric warming of
1976–77, and multidecadal temperature trends. Uncertainty estimates are based both on the spread of signal
estimates from the different observational datasets and on the inherent statistical uncertainties of the signal in
any individual dataset.
The large spread among trend estimates suggests that using multiple datasets to characterize large-scale upperair
temperature trends gives a more complete characterization of their uncertainty than reliance on a single
dataset. For other climate signals, there is value in using more than one dataset, because signal strengths vary.
However, the purely statistical uncertainty of the signal in individual datasets is large enough to effectively
encompass the spread among datasets. This result supports the notion of an 11th climate-monitoring principle,
augmenting the 10 principles that have now been generally accepted (although not generally implemented) by
the climate community. This 11th principle calls for monitoring key climate variables with multiple, independent
observing systems for measuring the variable, and multiple, independent groups analyzing the data
Controlling laser spectra in a phaseonium photonic crystal using maser
We study the control of quantum resonances in photonic crystals with
electromagnetically induced transparency driven by microwave field. In addition
to the control laser, the intensity and phase of the maser can alter the
transmission and reflection spectra in interesting ways, producing hyperfine
resonances through the combined effects of multiple scattering in the
superstructure.Comment: 7 pages, 4 figure
The spectrum of BPS branes on a noncompact Calabi-Yau
We begin the study of the spectrum of BPS branes and its variation on lines
of marginal stability on O_P^2(-3), a Calabi-Yau ALE space asymptotic to
C^3/Z_3. We show how to get the complete spectrum near the large volume limit
and near the orbifold point, and find a striking similarity between the
descriptions of holomorphic bundles and BPS branes in these two limits. We use
these results to develop a general picture of the spectrum. We also suggest a
generalization of some of the ideas to the quintic Calabi-Yau.Comment: harvmac, 45 pp. (v2: added references
Mutation in triangulated categories and rigid Cohen-Macaulay modules
We introduce the notion of mutation of -cluster tilting subcategories in a
triangulated category with Auslander-Reiten-Serre duality. Using this idea, we
are able to obtain the complete classifications of rigid Cohen-Macaulay modules
over certain Veronese subrings.Comment: 52 pages. To appear in Invent. Mat
Absolute Proper Motions to B~22.5: IV. Faint, Low Velocity White Dwarfs and the White Dwarf Population Density Law
The reduced proper motion diagram (RPMD) for a complete sample of faint stars
with high accuracy proper motions in the North Galactic Pole field SA57 is
investigated. Eight stars with very large reduced proper motions are identified
as faint white dwarf candidates. We discriminate these white dwarf candidates
from the several times more numerous QSOs based on proper motion and
variability.
We discuss the implausibility that these stars could be any kind of survey
contaminant. If {\it bona fide} white dwarfs, the eight candidates found here
represent a portion of the white dwarf population hitherto uninvestigated by
previous surveys by virtue of the faint magnitudes and low proper motions. The
newly discovered stars suggest a disk white dwarf scaleheight larger than the
values of 250-350 pc typically assumed in assessments of the local white dwarf
density. Both a <V/V_{max}> and a more complex maximum likelihood analysis of
the spatial distribution of our likely thin disk white dwarfs yield
scaleheights of 400-600 pc while at the same time give a reasonable match to
the local white dwarf volume density found in other surveys.
Our results could have interesting implications for white dwarfs as potential
MACHO objects. We can place some direct constraints (albeit weak ones) on the
contribution of halo white dwarfs to the dark matter of the Galaxy. Moreover,
the elevated scale height that we measure for the thin disk could alter the
interpretation of microlensing results to the extent of making white dwarfs
untenable as the dominant MACHO contributor. (Abridged)Comment: 38 pages, 5 figures, to appear in April Ap
Doped t-J Model on a Triangular Lattice: Possible Application to NaCoOH0 and NaTiO
We report the finding of time-reversal-symmetry-breaking superconducting ground state in the slave-boson mean-field theory for
the t-J model on triangular lattice. For () pairing exists for
() upon electron doping, and () upon hole
doping. These results are potentially relevant to doped Mott insulators
NaCoO.yHO and NaTiO.Comment: 3 figures, text polished, to appear in Phys. Rev.
Resonance enhanced isotope-selective photoionization of YbI for ion trap loading
Neutral Ytterbium (YbI) and singly ionized Ytterbium (YbII) is widely used in
experiments in quantum optics, metrology and quantum information science. We
report on the investigation of isotope selective two-photoionisation of YbI
that allows for efficient loading of ion traps with YbII. Results are presented
on two-colour (399 nm and 369 nm) and single-colour (399 nm) photoionisation
and their efficiency is compared to electron impact ionisation. Nearly
deterministic loading of a desired number of YbII ions into a linear Paul trap
is demonstrated.Comment: 9 pages. Considerably extended and revised version including new dat
Shrinking a large dataset to identify variables associated with increased risk of Plasmodium falciparum infection in Western Kenya
Large datasets are often not amenable to analysis using traditional single-step approaches. Here, our general objective was to apply imputation techniques, principal component analysis (PCA), elastic net and generalized linear models to a large dataset in a systematic approach to extract the most meaningful predictors for a health outcome. We extracted predictors for Plasmodium falciparum infection, from a large covariate dataset while facing limited numbers of observations, using data from the People, Animals, and their Zoonoses (PAZ) project to demonstrate these techniques: data collected from 415 homesteads in western Kenya, contained over 1500 variables that describe the health, environment, and social factors of the humans, livestock, and the homesteads in which they reside. The wide, sparse dataset was simplified to 42 predictors of P. falciparum malaria infection and wealth rankings were produced for all homesteads. The 42 predictors make biological sense and are supported by previous studies. This systematic data-mining approach we used would make many large datasets more manageable and informative for decision-making processes and health policy prioritization
Global Search for New Physics with 2.0/fb at CDF
Data collected in Run II of the Fermilab Tevatron are searched for
indications of new electroweak-scale physics. Rather than focusing on
particular new physics scenarios, CDF data are analyzed for discrepancies with
the standard model prediction. A model-independent approach (Vista) considers
gross features of the data, and is sensitive to new large cross-section
physics. Further sensitivity to new physics is provided by two additional
algorithms: a Bump Hunter searches invariant mass distributions for "bumps"
that could indicate resonant production of new particles; and the Sleuth
procedure scans for data excesses at large summed transverse momentum. This
combined global search for new physics in 2.0/fb of ppbar collisions at
sqrt(s)=1.96 TeV reveals no indication of physics beyond the standard model.Comment: 8 pages, 7 figures. Final version which appeared in Physical Review D
Rapid Communication
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