10,466 research outputs found
Simultaneous measurement of multiple parameters of a subwavelength structure based on the weak value formalism
A mathematical extension of the weak value formalism to the simultaneous
measurement of multiple parameters is presented in the context of an optical
focused vector beam scatterometry experiment. In this example, preselection and
postselection are achieved via spatially-varying polarization control, which
can be tailored to optimize the sensitivity to parameter variations. Initial
experiments for the two-parameter case demonstrate that this method can be used
to measure physical parameters with resolutions at least 1000 times smaller
than the wavelength of illumination
Affine transformations and analytic capacities
Analytic capacities are set functions defined on the plane which may be used in the study of removable singularities, boundary smoothness and approximation of analytic functions
belonging to some function space. The symmetric concrete Banach spaces form a class of function spaces that include most spaces usually studied. The Beurling transform is a
certain singular integral operator that has proved useful in analytic function theory. It is shown that the analytic capacity associated to each Beurling–invariant symmetric concrete Banach space behaves reasonably under affine transformation of the plane. It is not known how general analytic capacities behave under affine maps
Comparison of Nucleon Form Factors from Lattice QCD Against the Light Front Cloudy Bag Model and Extrapolation to the Physical Mass Regime
We explore the possibility of extrapolating state of the art lattice QCD
calculations of nucleon form factors to the physical regime. We find that the
lattice results can be reproduced using the Light Front Cloudy Bag Model by
letting its parameters be analytic functions of the quark mass. We then use the
model to extend the lattice calculations to large values of Q^{2} of interest
to current and planned experiments. These functions are also used to define
extrapolations to the physical value of the pion mass, thereby allowing us to
study how the predicted zero in G_{E}(Q^{2})/G_{M}(Q^{2}) varies as a function
of quark mass.Comment: 31 pages, 22 figure
Gluon polarization in the proton
We combine heavy-quark renormalization group arguments with our understanding
of the nucleon's wavefunction to deduce a bound on the gluon polarization Delta
g in the proton. The bound is consistent with the values extracted from spin
experiments at COMPASS and RHIC.Comment: 4 page
Wide-field weak lensing by RXJ1347-1145
We present an analysis of weak lensing observations for RXJ1347-1145 over a
43' X 43' field taken in B and R filters on the Blanco 4m telescope at CTIO.
RXJ1347-1145 is a massive cluster at redshift z=0.45. Using a population of
galaxies with 20<R<26, we detect a weak lensing signal at the p<0.0005 level,
finding best-fit parameters of \sigma_v=1400^{+130}_{-140} km s^{-1} for a
singular isothermal sphere model and r_{200} = 3.5^{+0.8}_{-0.2} Mpc with c =
15^{+64}_{-10} for a NFW model in an \Omega_m = 0.3, \Omega_\Lambda = 0.7
cosmology. In addition, a mass to light ratio M/L_R =90 \pm 20 M_\odot /
L_{R\odot} was determined. These values are consistent with the previous weak
lensing study of RXJ1347--1145 by Fischer and Tyson, 1997, giving strong
evidence that systemic bias was not introduced by the relatively small field of
view in that study. Our best-fit parameter values are also consistent with
recent X-ray studies by Allen et al, 2002 and Ettori et al, 2001, but are not
consistent with recent optical velocity dispersion measurements by Cohen and
Kneib, 2002.Comment: accepted to ApJ, tentative publication 10 May 2005, v624
Towards tactile sensing applied to underwater autonomous vehicles for near shore survey and de-mining
Artificial tactile whisker sensors demonstrate an approach to localisation [1] that is robust to harsh environmental disturbances, endowing autonomous systems with the ability to operate effectively in confined, noisy and visually occluded spaces, such as collapsed buildings or mine shafts, where conventional sensors become unreliable [2]. Marine engineering applications could benefit from such tactile sensors due to the lack of robust underwater close proximity sensing techniques. Animals such as walruses, seals and manatees all have exquisitely sensitive whiskers, which they use for hunting and foraging. Building upon a recent pilot study in underwater tactile sensing [3], we present the motivation for further research and our work plans toward a demonstrator platform for near shore survey and demining. © 2012 Springer-Verlag
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