1,721,020 research outputs found
Kawamata-Viehweg vanishing fails for log del Pezzo surfaces in characteristic 3
Full text linkWe construct a klt del Pezzo surface in characteristic three violating the Kawamata-Viehweg vanishing theorem. As a consequence we show that there exists a Kawamata log terminal threefold singularity which is not Cohen-Macaulay in characteristic three. (c) 2021 Elsevier B.V. All rights reserved
Non-normal purely log terminal centres in characteristic p >= 3
Full text linkWe show, building on a recent work of Totaro (The failure of Kodaira vanishing for Fano varieties, and terminal singularities that are not Cohen-Macaulay, 2017. arXiv:1710.04364v1), that for every prime number p >= 3 there exists a purely log terminal pair (Z, S) of dimension 2p + 2 whose plt centre S is not normal
On the base point free theorem for klt threefolds in large characteristic
Full text linkIn this article we present a refinement of the base point free theorem for threefolds in positive characteristic. If L is a nef Cartier divisor of numerical dimension at least one on a projective Kawamata log terminal threefold (X, 1) over a perfect field k of characteristic p >> 0 such that L - (K-X + 1) is big and nef, then we show that the linear system |mL| is base point free for all sufficiently large integers m > 0
Counterexamples to the MMP for 1-foliations in positive characteristic
Full text linkWe show that many statements of the Minimal Model Program, including the cone theorem, the base point free theorem and the existence of Mori fibre spaces, fail for 1-foliated surface pairs with canonical singularities in characteristic p>0
Vanishing Theorems for Three-folds in Characteristic p > 5
Full text linkWe prove Grauert-Riemenschneider-type vanishing theorems for excellent divisiorally log terminal threefolds pairs whose closed points have perfect residue fields of positive characteristic p > 5. Then we discuss applications to dlt singularities and to Mori fiber spaces of three-folds
Independent Regulation of Rap1 and Mitogen-Activated Protein Kinase by the alpha Chain of G(o)
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Bounding geometrically integral del Pezzo surfaces
Full text linkWe prove several boundedness statements for geometrically integral normal del Pezzo surfaces X over arbitrary fields. We give an explicit sharp bound on the irregularity if X is canonical or regular. In particular, we show that wild canonical del Pezzo surfaces exist only in characteristic
. As an application, we deduce that canonical del Pezzo surfaces form a bounded family over
, generalising work of Tanaka. More generally, we prove the BAB conjecture on the boundedness of
-klt del Pezzo surfaces over arbitrary fields of characteristic different from
and
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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