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We compute global log canonical thresholds, or equivalently alpha invariants, of birationally rigid orbifold Fano threefolds embedded in weighted projective spaces as codimension two or three. As an important application, we prove that most…

Algebraic Geometry · Mathematics 2016-04-04 In-Kyun Kim , Takuzo Okada , Joonyeong Won

We study birational automorphisms of algebraic varieties of bounded growth, i.e. such that the norms of the inverse images ${(f^n)}^* \colon \mathrm{NS}(X)\to \mathrm{NS}(X)$ of the powers of the automorphism $f\in\mathrm{Bir}(X)$ are…

Algebraic Geometry · Mathematics 2025-03-05 Alexandra Kuznetsova

We first elaborate on the theory of relative internality in stable theories, focusing on the notion of uniform relative internality (called collapse of the groupoid in an earlier work of the second author), and relating it to orthogonality,…

Logic · Mathematics 2020-09-15 Rémi Jaoui , Léo Jimenez , Anand Pillay

We have previously shown that the nonlinear growth of a finite-amplitude perturbation to a basic state given by a baroclinic zonal flow on the $\beta$-plane in a thermal quasigeostrophic reduced-gravity model can be a priori bounded. In…

Atmospheric and Oceanic Physics · Physics 2024-03-21 F. J. Beron-Vera

We derive a priori bounds on the size of the structure constants of the free Lie algebra over a set of indeterminates, relative to its Hall bases. We investigate their asymptotic growth, especially as a function of the length of the…

Combinatorics · Mathematics 2022-09-23 Karine Beauchard , Jérémy Le Borgne , Frédéric Marbach

We study the birational geometry of a Fano 4-fold X from the point of view of Mori dream spaces; more precisely, we study rational contractions of X. Here a rational contraction is a rational map f: X-->Y, where Y is normal and projective,…

Algebraic Geometry · Mathematics 2012-01-17 Cinzia Casagrande

A new tool for the model theory of differentially closed fields and of compact complex manifolds is here developed. In such settings, it is shown that a type internal to the field of constants (resp. to the projective line) admits a maximal…

Algebraic Geometry · Mathematics 2023-10-13 Rémi Jaoui , Rahim Moosa

In the paper two important theorems about complete affine spheres are generalized to the case of statistical structures on abstract manifolds. The assumption about constant sectional curvature is replaced by the assumption that the…

Differential Geometry · Mathematics 2018-05-22 Barbara Opozda

We propose a new method to study birational maps between Fano varieties based on multiplier ideal sheaves. Using this method, we prove equivariant birational rigidity of four Fano threefolds acted on by the group A6. As an application, we…

Algebraic Geometry · Mathematics 2011-12-08 Ivan Cheltsov , Constantin Shramov

This is the first in a series of papers about foliations in derived geometry. After introducing derived foliations on arbitrary derived stacks, we concentrate on quasi-smooth and rigid derived foliations on smooth complex algebraic…

Algebraic Geometry · Mathematics 2020-05-22 Bertrand Toën , Gabriele Vezzosi

We prove that in any fixed dimension, K-semistable log Fano cone singularities whose volumes are bounded from below by a fixed positive number form a bounded set. As a consequence, we show that the set of local volumes of klt singularities…

Algebraic Geometry · Mathematics 2024-08-22 Chenyang Xu , Ziquan Zhuang

We study closed, connected, spin 4-manifolds up to stabilisation by connected sums with copies of $S^2 \times S^2$. For a fixed fundamental group, there are primary, secondary and tertiary obstructions, which together with the signature…

Geometric Topology · Mathematics 2024-06-07 Daniel Kasprowski , Mark Powell , Peter Teichner

We show that the set of Fano varieties (with arbitrary singularities) whose anticanonical divisors have large Seshadri constants satisfies certain weak and birational boundedness. We also classify singular Fano varieties of dimension $n$…

Algebraic Geometry · Mathematics 2021-02-22 Ziquan Zhuang

We introduce a new, relatively simple, line-breaking construction of the $\alpha$-stable tree which realises its random finite-dimensional distributions. This is a direct analogue of Aldous' line-breaking construction of the Brownian…

Probability · Mathematics 2026-02-11 Christina Goldschmidt , Liam Hill

We consider pairs (X,A), where X is a variety with klt singularities and A is a formal product of ideals on X with exponents in a fixed set that satisfies the Descending Chain Condition. We also assume that X has (formally) bounded…

Algebraic Geometry · Mathematics 2010-06-25 Tommaso de Fernex , Lawrence Ein , Mircea Mustata

Motivated by Arveson's conjecture, we introduce a notion of hyperrigidity for a partial order on the state space of a $C^*$-algebra $B$. We show how this property is equivalent to the existence of a boundary: a subset of the pure states…

Operator Algebras · Mathematics 2023-10-27 Raphaël Clouâtre , Hridoyananda Saikia

We study rationality questions for Fano schemes of linear spaces on smooth complete intersections of two quadrics, especially over non-closed fields. Our approach is to study hyperbolic reductions of the pencil of quadrics associated to…

Algebraic Geometry · Mathematics 2025-07-31 Lena Ji , Fumiaki Suzuki

In this paper, we prove the openness of K-semistability in families of log Fano pairs by showing that the stability threshold is a constructible function on the fibers. We also prove that any special test configuration arises from a log…

Algebraic Geometry · Mathematics 2021-11-02 Harold Blum , Yuchen Liu , Chenyang Xu

We prove that there exist infinite families of regular bipartite Ramanujan graphs of every degree bigger than 2. We do this by proving a variant of a conjecture of Bilu and Linial about the existence of good 2-lifts of every graph. We also…

Combinatorics · Mathematics 2014-03-04 Adam Marcus , Daniel A. Spielman , Nikhil Srivastava

We prove boundedness of global strong $(\delta,n)$-complements for generalized $\epsilon$-log canonical pairs of Fano type. We also prove some partial results towards boundedness of local strong $(\delta,n)$-complements for semi-stable…

Algebraic Geometry · Mathematics 2021-08-12 Stefano Filipazzi , Joaquín Moraga
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