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We show that for a weak $\mathbb{Q}$-Fano threefold $X$ ($\mathbb{Q}$-factorial with terminal singularities and $-K_X$ is nef and big) of Picard rank $\rho(X)\leq 2$, either $-K_X^3\leq 64$ or $-K_X^3=72$ and…

Algebraic Geometry · Mathematics 2025-02-28 Ching-Jui Lai , Tsung-Ju Lee

Firstly, we see that the bases of the miniversal deformations of isolated $\mathbb{Q}$-Gorenstein toric singularities are quite restricted. In particular, we classify the analytic germs of embedding dimension $\leq 2$ which are the bases of…

Algebraic Geometry · Mathematics 2022-09-13 Andrea Petracci

We prove a structure theorem for projective varieties with nef anticanonical divisors.

Algebraic Geometry · Mathematics 2007-05-23 Qi Zhang

We give a simple necessary and sufficient condition for uniform K-stability of $\mathbb{Q}$-Fano varieties.

Algebraic Geometry · Mathematics 2016-09-20 Kento Fujita

A characterization of relative weak mixing in W*-dynamical systems in terms of a relatively independent joining is proven.

Operator Algebras · Mathematics 2021-08-31 Rocco Duvenhage , Malcolm King

We show that fixed dimensional klt weak Fano pairs with alpha-invariants and volumes bounded away from $0$ and the coefficients of the boundaries belonging to a fixed DCC set $S$ form a bounded family. Moreover, such pairs admit a strong…

Algebraic Geometry · Mathematics 2020-02-25 Weichung Chen

In this paper we find necessary and sufficient conditions for the weak convergence of c-free convolution of pairs of measures, where the measures are assumed to be infinitesimal and their support may be unbounded. These results are obtained…

Operator Algebras · Mathematics 2008-05-13 Jiun-Chau Wang

Inspired by Fujita's algebro-geometric result that complex projective space has maximal degree among all K-semistable complex Fano varieties, we conjecture that the height of a K-semistable metrized arithmetic Fano variety X of relative…

Algebraic Geometry · Mathematics 2024-11-20 Rolf Andreasson , Robert J. Berman

We give conditions for a uniruled variety of dimension at least 2 to be non-solid. This study provides further evidence to a conjecture by Abban and Okada on the solidity of Fano 3-folds. To complement our results we write explicit…

Algebraic Geometry · Mathematics 2023-07-07 Livia Campo , Tiago Duarte Guerreiro

We define a weak bimonad as a monad T on a monoidal category M with the property that the Eilenberg-Moore category M^T is monoidal and the forgetful functor from M^T to M is separable Frobenius. Whenever M is also Cauchy complete, a simple…

Category Theory · Mathematics 2014-05-21 Gabriella Böhm , Stephen Lack , Ross Street

In this notes we classify toric Fano 4-folds having positive second Chern Character.

Algebraic Geometry · Mathematics 2011-09-06 Edilaine Ervilha Nobili

For every complete toric variety, there exists a projective toric variety which is isomorphic to it in codimension one. In this paper, we show that every smooth non-projective complete toric threefold of Picard number at most five becomes…

Algebraic Geometry · Mathematics 2025-07-15 Osamu Fujino , Hiroshi Sato

A topological space ${\mathcal X}$ is reversible iff each continuous bijection (condensation) $f: {\mathcal X} \rightarrow {\mathcal X}$ is a homeomorphism; weakly reversible iff whenever ${\mathcal Y}$ is a space and there are…

General Topology · Mathematics 2024-12-11 Miloš S. Kurilić

The usual way of defining weak equivalences for simplicial presheaves is to require an isomorphism on all sheaves of homotopy groups. We unravel some of the machinery here, and give a more concrete description in terms of local homotopy…

Algebraic Topology · Mathematics 2007-05-23 Daniel Dugger , Daniel C. Isaksen

An inductive approach to classifying toric Fano varieties is given. As an application of this technique, we present a classification of the toric Fano threefolds with at worst canonical singularities. Up to isomorphism, there are 674,688…

Algebraic Geometry · Mathematics 2019-08-15 Alexander M. Kasprzyk

In this short note, we prove that the set of elementary tensors is weakly closed in the projective tensor product of two Banach spaces. As a result, we are able to answer a question from the literature proving that if $(x_n) \subset X$ and…

Functional Analysis · Mathematics 2025-03-19 Colin Petitjean

This paper gives an explicit computation of the category of constructible sheaves on a toric variety (with respect to the stratification by torus orbits). Over the complex numbers, this simplifies a description due to Braden and Lunts. The…

Algebraic Geometry · Mathematics 2024-10-10 Remy van Dobben de Bruyn

We investigate the extent to which the weak equivalences in a model category can be equipped with algebraic structure. We prove, for instance, that there exists a monad T such that a morphism of topological spaces admits T-algebra structure…

Category Theory · Mathematics 2022-01-31 John Bourke

We give an abstract definition of a hypertoric variety, generalizing the existing constructive definition. We construct a hypertoric variety associated with any zonotopal tiling, and we show that the previously known examples are exactly…

Algebraic Geometry · Mathematics 2015-12-01 Matthew Arbo , Nicholas Proudfoot

We give the first examples of flat fiber type contractions of Fano manifolds onto varieties that are not weak Fano, and we prove that these morphisms are Fano conic bundles. We also review some known results about the interaction between…

Algebraic Geometry · Mathematics 2017-03-09 Eleonora Anna Romano