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We report on the computation of torsion in certain homology theories of congruence subgroups of SL(4,Z). Among these are the usual group cohomology, the Tate-Farrell cohomology, and the homology of the sharbly complex. All of these theories…

Number Theory · Mathematics 2010-02-19 Avner Ash , Paul E. Gunnells , Mark McConnell

In this note we discuss some examples of non torsion and non algebraic cohomology classes for varieties over finite fields. The approach follows the construction of Atiyah-Hirzebruch and Totaro.

Algebraic Geometry · Mathematics 2014-01-09 Alena Pirutka , Nobuaki Yagita

We construct first examples of Fano varieties with torsion in their third cohomology group. The examples are constructed as double covers of linear sections of rank loci of symmetric matrices, and can be seen as higher-dimensional analogues…

Algebraic Geometry · Mathematics 2023-11-17 John Christian Ottem , Jørgen Vold Rennemo

The main purpose of this paper is to generalize the celebrated L${}^2$ extension theorem of Ohsawa-Takegoshi in several directions : the holomorphic sections to extend are taken in a possibly singular hermitian line bundle, the subvariety…

Algebraic Geometry · Mathematics 2017-05-24 Junyan Cao , Jean-Pierre Demailly , Shin-Ichi Matsumura

We show that (under mild assumptions) the generating function of log homology torsion of a knot exterior has a meromorphic continuation to the entire complex plane. As corollaries, this gives new proofs of (a) the Silver-Williams…

Geometric Topology · Mathematics 2017-02-22 Oliver Braunling

Let $B$ be the split extension of a finite dimensional algebra $C$ by a $C$-$C$-bimodule $E$. We define a morphism of associative graded algebras $\varphi^*:\HH^*(B)\rightarrow \HH^*(C)$ from the Hochschild cohomology of $B$ to that of $C$,…

Representation Theory · Mathematics 2016-02-03 Ibrahim Assem , M. Andrea Gatica , Ralf Schiffler , Rachel Taillefer

We characterize the Hurewicz cofibrations between finite topological spaces, that is, the continuous functions between finite topological spaces that have the homotopy extension property with respect to all topological spaces. In…

Algebraic Topology · Mathematics 2018-02-28 Nicolás Cianci , Miguel Ottina

We establish a structure theorem for the connected automorphism groups of smooth complete toroidal horospherical varieties, that is, toric fibrations over rational homogeneous spaces. The key ingredient is a characterization of the Demazure…

Algebraic Geometry · Mathematics 2026-03-10 Lorenzo Barban , DongSeon Hwang , Minseong Kwon

Let F be a fibration on a simply-connected base with symplectic fibre (M, \omega). Assume that the fibre is nilpotent and T^{2k}-separable for some integer k or a nilmanifold. Then our main theorem, Theorem 1.8, gives a necessary and…

Algebraic Topology · Mathematics 2011-08-04 Katsuhiko Kuribayashi

In the case of toric varieties, we continue the pursuit of Kontsevich's fundamental insight, Homological Mirror Symmetry, by unifying it with the Mori program. We give a refined conjectural version of Homological Mirror Symmetry relating…

Algebraic Geometry · Mathematics 2013-02-05 Matthew Ballard , Colin Diemer , David Favero , Ludmil Katzarkov , Gabriel Kerr

We study the growth of the order of torsion subgroups of the homology in a tower of finite abelian coverings. In particular, we prove that it is exponential for when the tower converges to the maximal free abelian cover of a link complement…

Geometric Topology · Mathematics 2014-10-01 Jean Raimbault

We characterise and investigate co-Higgs sheaves and associated algebraic and combinatorial invariants on toric varieties. In particular, we compute explicit examples.

Algebraic Geometry · Mathematics 2020-10-20 Klaus Altmann , Frederik Witt

We show that a toric Fano contraction associated to an extremal ray whose length is greater than the dimension of its fiber is a projective space bundle.

Algebraic Geometry · Mathematics 2018-08-20 Osamu Fujino , Hiroshi Sato

If a mapping of several complex variables into projective space is holomorphic in each pair of variables, then it is globally holomorphic.

Complex Variables · Mathematics 2007-05-23 P. M. Gauthier , E. S. Zeron

This article is concerned with the convexity properties of universal covers of projective varieties. We study the relation between the convexity properties of the universal cover of X and the properties of the pullback map sending vector…

Algebraic Geometry · Mathematics 2007-05-23 F. Bogomolov , B. De Oliveira

We discuss the problem of the existence of envelopes of holomorphy of the A-crosses, which leads us to the far-reaching generalizations of the famous Hartogs theorem. We also take under consideration the issue of the existence of "nice"…

Complex Variables · Mathematics 2013-04-24 Arkadiusz Lewandowski

We show that the (toric) local height of a toric variety with respect to a semipositive torus-invariant singular metric is given by the integral of a concave function over a compact convex set. This generalizes a result of Burgos,…

Algebraic Geometry · Mathematics 2026-01-21 Gari Y. Peralta Alvarez

Let X be a Zariski open subset of a compact Kaehler manifold. In this paper, we study the set $\Sigma^k(X)$ of one dimensional local systems on X with nonvanishing kth cohomology. We show that under certain conditions (X compact, X has a…

alg-geom · Mathematics 2008-02-03 Donu Arapura

We generalize classical results about the topology of toric varieties to the case of projective Q-factorial T-varieties of complexity one using the language of divisorial fans. We describe the Hodge-Deligne polynomial in the smooth case,…

Algebraic Geometry · Mathematics 2017-12-07 Antonio Laface , Alvaro Liendo , Joaquín Moraga

We prove that the cohomology of the moduli space of morphisms of a fixed finite degree from a smooth projective curve $C$ of genus $g$ to a complete simplicial toric variety $\mathbb{P}(\Sigma)$, denoted by the rational polyhedral fan…

Algebraic Geometry · Mathematics 2022-10-13 Oishee Banerjee