133,769 research outputs found

    Reduced classes and curve counting on surfaces II: calculations

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    We calculate the stable pair theory of a projective surface SS. For fixed curve class βH2(S)\beta\in H^2(S) the results are entirely topological, depending on β2\beta^2, β.c1(S)\beta.c_1(S), c1(S)2c_1(S)^2, c2(S)c_2(S), b1(S)b_1(S) \emph{and} invariants of the ring structure on H(S)H^*(S) such as the Pfaffian of β\beta considered as an element of Λ2H1(S)\Lambda^2 H^1(S)^*. Amongst other things, this proves an extension of the G\"ottsche conjecture to non-ample linear systems. We also give conditions under which this calculates the full 3-fold reduced residue theory of KSK_S. This is related to the reduced residue Gromov-Witten theory of SS via the MNOP conjecture. When the surface has no holomorphic 2-forms this can be expressed as saying that certain Gromov-Witten invariants of SS are topological. Our method uses the results of \cite{KT1} to express the reduced virtual cycle in terms of Euler classes of bundles over a natural smooth ambient space.Comment: 19 pages. Minor correction

    Anomalous Hall effect in the Co-based Heusler compounds Co2_{2}FeSi and Co2_{2}FeAl

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    The anomalous Hall effect (AHE) in the Heusler compounds Co2_{2}FeSi and Co2_{2}FeAl is studied in dependence of the annealing temperature to achieve a general comprehension of its origin. We have demonstrated that the crystal quality affected by annealing processes is a significant control parameter to tune the electrical resistivity ρxx\rho_{xx} as well as the anomalous Hall resistivity ρahe\rho_{ahe}. Analyzing the scaling behavior of ρahe\rho_{ahe} in terms of ρxx\rho_{xx} points to a temperature-dependent skew scattering as the dominant mechanism in both Heusler compounds

    Working Effectively with Persons who have Cognitive Disabilities

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    This brochure on cognitive disabilities and the American with Disabilities Act is one of a series on human resources practices and workplace accommodations for persons with disabilities edited by Susanne M. Bruyère, Ph.D., CRC, SPHR, Director, Program on Employment and Disability, School of Industrial and Labor Relations – Extension Division, Cornell University. Cornell University was funded in the early 1990’s by the U.S. Department of Education National Institute on Disability and Rehabilitation Research as a National Materials Development Project on the employment provisions (Title I) of the ADA (Grant #H133D10155). These updates, and the development of new brochures, have been funded by Cornell’s Program on Employment and Disability, the Pacific Disability and Business Technical Assistance Center, and other supporters

    Geographical catch distribution of yellowfin and skipjack tuna in the Eastern Pacific Ocean, 1967-1970, and fleet and total catch statistics, 1962-1970

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    ENGLISH: Logbook records of tuna vessels fishing in the eastern Pacific Ocean were used to prepare charts showing the distribution of yellowfin tuna and skipjack catches by i-degree area, by quarter of the year, and by gear, for the years 1967-1970. Recent changes in the geographical distribution of yellowfin catch are illustrated. Also given are annual catch statistics and the composition of the international tuna fishing fleets which operated in the Commission's Yellowfin Regulatory Area each year, 1962-1970. SPANISH: Los registros de los cuadernos de bitácora de los barcos pesqueros de atún en el Océano Pacífico oriental se usaron para preparar gráficos que presentan para los años de 1967-1970, la distribución de captura del atún aleta amarilla y barrilete por área de 1 grado, trimestre del año y, por las artes. Se ilustran los recientes cambios en la distribución geográfica de la captura del atún aleta amarilla. Se presentan también las estadísticas de captura anual y la composición de la flota internacional de pesca, que explota cada año el Area Reglamentaria de la Comisión, 1962-1970. (PDF contains 95 pages.

    The role of active galactic nuclei in galaxy formation

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    We use Monte-Carlo Markov chain techniques to constrain acceptable parameter regions for the Munich L-Galaxies semi-analytic galaxy formation model. Feedback from active galactic nuclei (AGN) is required to limit star-formation in the most massive galaxies. However, we show that the introduction of tidal stripping of dwarf galaxies as they fall into and merge with their host systems can lead to a reduction in the required degree of AGN feedback. In addition, the new model correctly reproduces both the metallicity of large galaxies and the fraction of intracluster light.Comment: Monster's Fiery Breath Conference Proceedings, 4 page

    The First Moments of Nucleon Generalized Parton Distributions

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    We extrapolate the first moments of the generalized parton distributions using heavy baryon chiral perturbation theory. The calculation is based on the one loop level with the finite range regularization. The description of the lattice data is satisfactory and the extrapolated moments at physical pion mass are consistent with the results obtained with dimensional regularization, although the extrapolation in the momentum transfer to t=0t=0 does show sensitivity to form factor effects which lie outside the realm of chiral perturbation theory. We discuss the significance of the results in the light of modern experiments as well as QCD inspired models.Comment: 14 pages, 9 figure

    Quark structure and nuclear effective forces

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    We formulate the quark meson coupling model as a many-body effective Hamiltonian. This leads naturally to the appearance of many-body forces. We investigate the zero range limit of the model and compare its Hartree-Fock Hamiltonian to that corresponding to the Skyrme effective force. By fixing the three parameters of the model to reproduce the binding and symmetry energy of nuclear matter, we find that it allows a very satisfactory interpretation of the Skyrme force.Comment: 4 pages, 1tabl
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