38,639 research outputs found
Structure of logarithmically divergent one-loop lattice Feynman integrals
For logarithmically divergent one-loop lattice Feynman integrals I(p,a),
subject to mild general conditions, we prove the following expected and crucial
structural result: I(p,a) = f(p)log(aM)+g(p)+h(p,M) up to terms which vanish
for lattice spacing a -> 0. Here p denotes collectively the external momenta
and M is a mass scale which may be chosen arbitrarily. The f(p) and h(p,M) are
shown to be universal and coincide with analogous quantities in the
corresponding continuum integral when the latter is regularized either by
momentum cut-off or dimensional regularization. The non-universal term g(p) is
shown to be a homogeneous polynomial in p of the same degree as f(p). This
structure is essential for consistency between renormalized lattice and
continuum formulations of QCD at one loop.Comment: 26 pages (after reformatting using revtex); typos corrected; to
appear in Phys.Rev.
Spin Readout Techniques of the Nitrogen-Vacancy Center in Diamond
The diamond nitrogen-vacancy (NV) center is a leading platform for quantum
information science due to its optical addressability and room-temperature spin
coherence. However, measurements of the NV center's spin state typically
require averaging over many cycles to overcome noise. Here, we review several
approaches to improve the readout performance and highlight future avenues of
research that could enable single-shot electron-spin readout at room
temperature.Comment: 21 pages, 7 figure
The Use of Multi-beam Sonars to Image Bubbly Ship Wakes
During the past five years, researchers at Penn State University (PSU) have used upward-looking multi-beam (MB) sonar to image the bubbly wakes of surface ships. In 2000, a 19-beam, 5° beam width, 120° sector, 250 kHz MB sonar integrated into an autonomous vehicle was used to obtain a first-of-a-kind look at the three-dimensional variability of bubbles in a large ship wake. In 2001 we acquired a Reson 8101 MB sonar, which operates at 240 kHz and features 101-1.5º beams spanning a 150º sector. In July 2002, the Reson sonar was deployed looking upward from a 1.4 m diameter buoy moored at 29.5 m depth in 550 m of water using three anchor lines. A fiber optic cable connected the sonar to a support ship 500 m away. Images of the wake of a small research vessel provided new information about the persistence of bubble clouds in the ocean. An important goal is to use the MB sonar to estimate wake bubble distributions, as has been done with single beam sonar. Here we show that multipath interference and strong, specular reflections from the sea surface adversely affect the use of MB sonars to unambiguously estimate wake bubble distributio
Frequency stabilization of an external-cavity diode laser
Using a hybrid optical/electronic technique, an external-cavity diode laser was frequency stabilized with respect to the sub-Doppler spectrum of cesium vapor. Laser linewidths of 65 kHz and frequency stabilities of ±10 kHz were obtained
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