23,106 research outputs found

    Extensions of Johnson's and Morita's homomorphisms that map to finitely generated abelian groups

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    We extend each higher Johnson homomorphism to a crossed homomorphism from the automorphism group of a finite-rank free group to a finite-rank abelian group. We also extend each Morita homomorphism to a crossed homomorphism from the mapping class group of once-bounded surface to a finite-rank abelian group. This improves on the author's previous results [Algebr. Geom. Topol. 7 (2007):1297-1326]. To prove the first result, we express the higher Johnson homomorphisms as coboundary maps in group cohomology. Our methods involve the topology of nilpotent homogeneous spaces and lattices in nilpotent Lie algebras. In particular, we develop a notion of the "polynomial straightening" of a singular homology chain in a nilpotent homogeneous space.Comment: 34 page

    Single spin asymmetry in high energy QCD

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    We present the first steps in an effort to incorporate the physics of transverse spin asymmetries into the saturation formalism of high energy QCD. We consider a simple model in which a transversely polarized quark scatters on a proton or nuclear target. Using the light-cone perturbation theory the hadron production cross section can be written as a convolution of the light-cone wave function squared and the interaction with the target. To generate the single transverse spin asymmetry (STSA) either the wave function squared or the interaction with the target has to be T-odd. In this work we use the lowest-order q->qG wave function squared, which is T-even, generating the STSA from the T-odd interaction with the target mediated by an odderon exchange. We study the properties of the obtained STSA, some of which are in qualitative agreement with experiment: STSA increases with increasing projectile x_F and is a non-monotonic function of the transverse momentum k_T. Our mechanism predicts that the quark STSA in polarized proton--nucleus collisions should be much smaller than in polarized proton--proton collisions. We also observe that the STSA for prompt photons due to our mechanism is zero within the accuracy of the approximation.Comment: 10 pages, 6 figures, proceedings of the QCD Evolution Workshop, May 14 - 17, 2012, Thomas Jefferson National Accelerator Facility, Newport News, V

    Top 10 Law School Home Pages of 2012

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    For a fourth consecutive year, every website home page of every ABA-accredited law school is evaluated and ranked based on objective criteria. The goal is to identify well-executed sites adopting best practices. For the 2012 report, twenty-six elements are evaluated across these three categories: Design Patterns and Metadata, Accessibility and Validation, & Marketing and Communications. For 2012, there are four new elements, two prior elements have been combined, and one element was dropped. For 2012, forty-six schools now use the HTML5 doctype, which is up from thirteen in 2011 and just one in 2010. Eighteen schools achieve perfect scores in an adjusted web accessibility evaluation, which is a slight increase over previous years. One of the new elements awards points for use of Responsive Web Design practices, which is a page layout method that shifts the order and number of elements on a page, based on the screen size displaying the content. Our survey discovered fourteen home pages using responsive web design. As has been the case since this annual study launched in 2009, there is still no objective way to account for good taste. For interpreting these results, please decide for yourself whether any home page is greater or less than the sum of its evaluated elements

    Sivers Function in the Quasi-Classical Approximation

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    We calculate the Sivers function in semi-inclusive deep inelastic scattering (SIDIS) and in the Drell-Yan process (DY) by employing the quasi-classical Glauber-Mueller/ McLerran-Venugopalan approximation. Modeling the hadron as a large "nucleus" with non-zero orbital angular momentum (OAM), we find that its Sivers function receives two dominant contributions: one contribution is due to the OAM, while another one is due to the local Sivers function density in the nucleus. While the latter mechanism, being due to the "lensing" interactions, dominates at large transverse momentum of the produced hadron in SIDIS or of the di-lepton pair in DY, the former (OAM) mechanism is leading in saturation power counting and dominates when the above transverse momenta become of the order of the saturation scale. We show that the OAM channel allows for a particularly simple and intuitive interpretation of the celebrated sign flip between the Sivers functions in SIDIS and DY.Comment: 44 pages, 14 figures; v2: typos corrected, figure modifie

    Using Charge Asymmetries to Measure Single Top Quark Production at the LHC

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    Electroweak production of single top quarks is an as-yet-unverified prediction of the Standard model, potentially sensitive to new physics. Two of the single top quark productions channels have significant charge asymmetries at the LHC, while the much larger background from ttˉt\bar{t} is nearly charge-symmetric. This can be used to reduce systematic uncertainties and make precision measurements of single top quark production.Comment: 4 pages, 1 figur

    Evaluating cultural competency and patient satisfaction in an urban dermatology clinic.

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    Cultural competency continues to gain increased attention in medicine. Not only does it play a significant role in the delivery of health care and patient outcomes, but it also remains a major determinant of patient satisfaction. This study investigated how patients in an urban dermatology clinic rated their satisfaction with cultural competency. Compared to White patients, satisfaction scores were greater for Hispanic or Latino patients and less for Asian patients, while there was no significant difference for Black or African American patients. There were clear differences in patient satisfaction rates of various dimensions of cultural competency. A follow-up study with a larger sample size is needed for closer examination into the conclusions
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