6,842 research outputs found
Information on the structure of the a1 from tau decay
The decay is analysed using different methods to
account for the resonance structure, which is usually ascribed to the a1. One
scenario is based on the recently developed techniques to generate axial-vector
resonances dynamically, whereas in a second calculation the a1 is introduced as
an explicit resonance. We investigate the influence of different assumptions on
the result. In the molecule scenario the spectral function is described
surprisingly well by adjusting only one free parameter. This result can be
systematically improved by adding higher order corrections to the iterated
Weinberg-Tomozawa interaction. Treating the a1 as an explicit resonance on the
other hand leads to peculiar properties
Relativistically invariant quantum information
We show that quantum information can be encoded into entangled states of
multiple indistinguishable particles in such a way that any inertial observer
can prepare, manipulate, or measure the encoded state independent of their
Lorentz reference frame. Such relativistically invariant quantum information is
free of the difficulties associated with encoding into spin or other degrees of
freedom in a relativistic context.Comment: 5 pages, published versio
Gravity from a fermionic condensate of a gauge theory
The most prominent realization of gravity as a gauge theory similar to the
gauge theories of the standard model comes from enlarging the gauge group from
the Lorentz group to the de Sitter group. To regain ordinary Einstein-Cartan
gravity the symmetry must be broken, which can be accomplished by known
quasi-dynamic mechanisms. Motivated by symmetry breaking models in particle
physics and condensed matter systems, we propose that the symmetry can
naturally be broken by a homogenous and isotropic fermionic condensate of
ordinary spinors. We demonstrate that the condensate is compatible with the
Einstein-Cartan equations and can be imposed in a fully de Sitter invariant
manner. This lends support, and provides a physically realistic mechanism for
understanding gravity as a gauge theory with a spontaneously broken local de
Sitter symmetry.Comment: 16 page
Relativistically covariant state-dependent cloning of photons
The influence of the relativistic covariance requirement on the optimality of
the symmetric state-dependent 1 -> 2 cloning machine is studied. Namely, given
a photonic qubit whose basis is formed from the momentum-helicity eigenstates,
the change to the optimal cloning fidelity is calculated taking into account
the Lorentz covariance unitarily represented by Wigner's little group. To
pinpoint some of the interesting results, we found states for which the optimal
fidelity of the cloning process drops to 2/3 which corresponds to the fidelity
of the optimal classical cloner. Also, an implication for the security of the
BB84 protocol is analyzed.Comment: corrected, rewritten and accepted in PR
Comment on "Reinterpreting aircraft measurement in anisotropic scaling turbulence" by Lovejoy et al. (2009)
Recently, Lovejoy et al. (2009) argued that the steep ~k−3 atmospheric kinetic energy spectrum at synoptic scales (≥1000 km) observed by aircraft is a spurious artefact of aircraft following isobars instead of isoheights. Without taking into account the earth's rotation they hypothesise that the horizontal atmospheric energy spectrum should scale as k−5/3 at all scales. We point out that the approximate k−3-spectrum at synoptic scales has been observed by a number of non-aircraft means since the 1960s and that general circulation models and other current models have successfully produced this spectrum. We also argue that the vertical movements of the aircraft are far too small to cause any strong effect on the measured spectrum at synoptic scales
How should one formulate, extract, and interpret `non-observables' for nuclei?
Nuclear observables such as binding energies and cross sections can be
directly measured. Other physically useful quantities, such as spectroscopic
factors, are related to measured quantities by a convolution whose
decomposition is not unique. Can a framework for these nuclear structure
`non-observables' be formulated systematically so that they can be extracted
from experiment with known uncertainties and calculated with consistent theory?
Parton distribution functions in hadrons serve as an illustrative example of
how this can be done. A systematic framework is also needed to address
questions of interpretation, such as whether short-range correlations are
important for nuclear structure.Comment: 7 pages. Contribution to the "Focus issue on Open Problems in Nuclear
Structure", Journal of Physics
Heavy Quark Production and PDF's Subgroup Report
We present a status report of a variety of projects related to heavy quark
production and parton distributions for the Tevatron Run II.Comment: Latex. 8 pages, 7 eps figures. Contribution to the Physics at Run II
Workshops: QCD and Weak Boson Physic
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Fibronectin Synthesis is a Marker for Peritubular Cell Contaminants in Sertoli Cell-Enriched Cultures
With indirect immunofluorescent microscopic techniques, we have shown that fibronectin is distributed primarily in or along the basal lamina of the seminiferous tubule boundary tissue in sections of testes from 20-day-old rats. Purified rat Sertoli cell-enriched aggregates, maintained in culture in the presence or absence of serum, exhibit no detectable immunofluorescence with fibronectin antibody, whereas purified peritubular cells in culture do have a positive reaction to fibronectin antibody. Peritubular cells in culture incorporate [35S] methionine into fibronectin which can be immunoprecipitated with a fibronectin antiserum, but Sertoli cells do not. We have used various criteria to estimate the degree of purity of Sertoli cell-enriched preparations. The presence of peritubular myoid cells in conventional Sertoli cell-enriched aggregates, cultured in the presence or absence of serum, can be detected with transmission electron microscopic examination, by the Feulgen staining procedure, and by the immunocytochemical identification of fibronectin. We describe a technique to purify Sertoli cells in conventional Sertoli cell-enriched preparations by treatment with hyaluronidase, resulting in a lesser number of peritubular cells by the above criteria, even in preparations cultured in the presence of serum. Data presented suggest that some of the products previously attributed exclusively to Sertoli cells in Sertoli cell-enriched preparations, particularly those cultured in the presence of serum, may have been contributed by peritubular cells
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