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Twisted stable maps to tame Artin stacks
Full text linkWe develop the theory of twisted stable maps into a tame Artin stack M. We show that the stacks K(g,n)(M) of twisted stable maps are algebraic, and proper and quasi-finite over the corresponding stacks K(g,n)(M) of stable maps of the coarse moduli space M of M. In the special case where M = BC, the classifying stack of a linearly reductive group scheme G, we show that K(g,n)(BG) -> (M) over bar (g,n) is a flat morphism with local complete intersection fibers
Expanded degenerations and pairs
No full textWe provide a universal approach to the moduli of Jun Li's expanded pairs and expanded degenerations. This enables us to prove algebraicity results, compare with Li's approach and with the approach of Graber and Vakil, and generalize to the twisted expansions used by Abramovich and Fantechi as a basis for orbifold techniques in degeneration formulas
Twisted bundles and admissible covers
No full textWe study the structure of the stacks of twisted stable maps to the classifying stack of. a finite group G-which we call the stack of twisted G-covers, or twisted G-bundles. For a suitable group G we show that the substack. corresponding to admissible G-covers is a smooth projective fine moduli space
Tame stacks in positive characteristic
Full text linkWe introduce and study a class of algebraic stacks with finite inertia in positive and mixed characteristic, which we call tame algebraic stacks. They include tame Deligne-Mumford stacks, and are arguably better behaved than general Deligne-Mumford stacks. We also give a complete characterization of finite flat linearly reductive schemes over an arbitrary base. Our main result is that tame algebraic stacks are etale locally quotient by actions of linearly reductive finite group schemes
Gromov-Witten theory of Deligne-Mumford stacks
Full text linkGiven a smooth complex Deligne-Mumford stack X with a projective coarse moduli space. we introduce Gromov-Witten invariants of X and prove some of their basic properties, including the WDVV equation
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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