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On fundamental groups of algebraic varieties and value distribution theory

Katsutoshi Yamanoi (2010)

Annales de l’institut Fourier

If a smooth projective variety X admits a non-degenerate holomorphic map X from the complex plane , then for any finite dimensional linear representation of the fundamental group of X the image of this representation is almost abelian. This supports a conjecture proposed by F. Campana, published in this journal in 2004.

On generalized “ham sandwich” theorems

Marek Golasiński (2006)

Archivum Mathematicum

In this short note we utilize the Borsuk-Ulam Anitpodal Theorem to present a simple proof of the following generalization of the “Ham Sandwich Theorem”: Let A 1 , ... , A m n be subsets with finite Lebesgue measure. Then, for any sequence f 0 , ... , f m of -linearly independent polynomials in the polynomial ring [ X 1 , ... , X n ] there are real numbers λ 0 , ... , λ m , not all zero, such that the real affine variety { x n ; λ 0 f 0 ( x ) + + λ m f m ( x ) = 0 } simultaneously bisects each of subsets A k , k = 1 , ... , m . Then some its applications are studied.

On generation of jets for vector bundles.

Mauro C. Beltrametti, Sandra Di Rocco, Andrew J. Sommese (1999)

Revista Matemática Complutense

We introduce and study the k-jet ampleness and the k-jet spannedness for a vector bundle, E, on a projective manifold. We obtain different characterizations of projective space in terms of such positivity properties for E. We compare the 1-jet ampleness with different notions of very ampleness in the literature.

On geometry of binary symmetric models of phylogenetic trees

Weronika Buczyńska, Jaroslaw A. Wiśniewski (2007)

Journal of the European Mathematical Society

We investigate projective varieties which are binary symmetric models of trivalent phylogenetic trees. We prove that they have Gorenstein terminal singularities and are Fano varieties of index 4 and dimension equal to the number of edges of the tree in question. Moreover any two such varieties which are of the same dimension are deformation equivalent, that is, they are in the same connected component of the Hilbert scheme of the projective space. As an application we provide a simple formula for...

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