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The Kähler Ricci flow on Fano manifolds (I)

Xiuxiong Chen, Bing Wang (2012)

Journal of the European Mathematical Society

We study the evolution of pluri-anticanonical line bundles K M - ν along the Kähler Ricci flow on a Fano manifold M . Under some special conditions, we show that the convergence of this flow is determined by the properties of the pluri-anticanonical divisors of M . For example, the Kähler Ricci flow on M converges when M is a Fano surface satisfying c 1 2 ( M ) = 1 or c 1 2 ( M ) = 3 . Combined with the works in [CW1] and [CW2], this gives a Ricci flow proof of the Calabi conjecture on Fano surfaces with reductive automorphism groups....

The Kodaira dimension of the moduli space of Prym varieties

Gavril Farkas, Katharina Ludwig (2010)

Journal of the European Mathematical Society

We study the enumerative geometry of the moduli space g of Prym varieties of dimension g - 1 . Our main result is that the compactication of g is of general type as soon as g > 13 and g is different from 15. We achieve this by computing the class of two types of cycles on g : one defined in terms of Koszul cohomology of Prym curves, the other defined in terms of Raynaud theta divisors associated to certain vector bundles on curves. We formulate a Prym–Green conjecture on syzygies of Prym-canonical curves....

The KSBA compactification for the moduli space of degree two K 3 pairs

Radu Laza (2016)

Journal of the European Mathematical Society

Inspired by the ideas of the minimal model program, Shepherd-Barron, Kollár, and Alexeev have constructed a geometric compactification for the moduli space of surfaces of log general type. In this paper, we discuss one of the simplest examples that fits into this framework: the case of pairs ( X , H ) consisting of a degree two K 3 surface X and an ample divisor H . Specifically, we construct and describe explicitly a geometric compactification P ¯ 2 for the moduli of degree two K 3 pairs. This compactification...

The Lamé family of connections on the projective line

Frank Loray, Marius van der Put, Felix Ulmer (2008)

Annales de la faculté des sciences de Toulouse Mathématiques

This paper deals with rank two connections on the projective line having four simple poles with prescribed local exponents 1/4 and - 1 / 4 . This Lamé family of connections has been extensively studied in the literature. The differential Galois group of a Lamé connection is never maximal : it is either dihedral (finite or infinite) or reducible. We provide an explicit moduli space of those connections having a free underlying vector bundle and compute the algebraic locus of those reducible connections....

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