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A Fano variety of Picard number $1$ is said to be \textit{birationally solid} if it is not birational to a Mori fiber space over a positive dimensional base. In this paper we complete the classification of quasi-smooth birationally solid…

Algebraic Geometry · Mathematics 2023-09-12 Takuzo Okada

A complex smooth prime Fano threefold $X$ of genus $9$ is related via projective duality to a quartic plane curve $\Gamma$. We use this setup to study the restriction of rank $2$ stable sheaves with prescribed Chern classes on $X$ to an…

Algebraic Geometry · Mathematics 2024-01-08 Dominique Mattei

We introduce a new boundedness condition for affine permutations, motivated by the fruitful concept of periodic boundary conditions in statistical physics. We study pattern avoidance in bounded affine permutations. In particular, we show…

Combinatorics · Mathematics 2023-06-22 Neal Madras , Justin M. Troyka

In this article we prove a local implication of boundedness of Fano varieties. More precisely, we prove that $d$-dimensional $a$-log canonical singularities, with standard coefficients, which admit an $\epsilon$-plt blow-up have minimal log…

Algebraic Geometry · Mathematics 2018-10-25 Joaquín Moraga

We prove that a family of varieties is birationally isotrivial if all the fibers are birational to each other.

Algebraic Geometry · Mathematics 2017-09-18 Fedor Bogomolov , Christian Böhning , Hans-Christian Graf von Bothmer

We prove finite generation of the algebra of type A conformal blocks over arbitrary stable curves of any genus. As an application we construct a flat family of irreducible normal projective varieties over the moduli stack of stable pointed…

Algebraic Geometry · Mathematics 2019-09-11 Han-Bom Moon , Sang-Bum Yoo

This paper demonstrates the existence of $\mathbb{Q}$-complements for algebraically integrable log-Fano foliations on klt ambient varieties. Additionally, we investigate properties of algebraically integrable Fano foliations such as a…

Algebraic Geometry · Mathematics 2024-08-22 Yen-An Chen , Dongchen Jiao , Pascale Voegtli

Let $f:\, X\to Y$ be a semistable non-isotrivial family of $n$-folds over a smooth projective curve with discriminant locus $S \subseteq Y$ and with general fibre $F$ of general type. We show the strict Arakelov inequality…

Algebraic Geometry · Mathematics 2022-01-07 Xin Lu , Jinbang Yang , Kang Zuo

In this paper we prove a result on the effective generation of pluri-canonical linear systems on foliated surfaces of general type. Fix a function $P: \mathbb Z_{\geq 0}\to \mathbb Z $, then there exists an integer $N_1>0$ such that if…

Algebraic Geometry · Mathematics 2025-01-13 Christopher D. Hacon , Adrian Langer

We consider a class of foliations on the complex projective plane that are determined by a quadratic vector field in a fixed affine neighborhood. Such foliations, as a rule, have an invariant line at infinity. Two foliations with…

Dynamical Systems · Mathematics 2010-10-28 Yulij Ilyashenko , Vadims Moldavskis

We introduce bilinear secant varieties and joins of subvarieties of products of projective spaces, as a generalisation of the classical secant varieties and joins of projective varieties. We show that the bilinear secant varieties of…

Algebraic Geometry · Mathematics 2026-02-27 Elisa Postinghel , Artie Prendergast-Smith

We study a notion of VC-dimension for subsets of groups, defining this for a set $A$ to be the VC-dimension of the family $\{ (xA) \cap A : x \in A\cdot A^{-1} \}$. We show that if a finite subset $A$ of an abelian group has bounded…

Combinatorics · Mathematics 2021-03-26 Olof Sisask

We construct klt projective varieties with ample canonical class and the smallest known volume. We also find exceptional klt Fano varieties with the smallest known anticanonical volume. We conjecture that our examples have the smallest…

Algebraic Geometry · Mathematics 2022-11-03 Burt Totaro

Shokurov conjectured that the set of all log canonical thresholds on varieties of bounded dimension satisfies the ascending chain condition. In this paper we prove that the conjecture holds for log canonical thresholds on smooth varieties…

Algebraic Geometry · Mathematics 2019-12-19 Tommaso de Fernex , Lawrence Ein , Mircea Mustata

For a birational log Fano contraction, it is conjectured an inequality between the dimension of its exceptional locus and the minimal log discrepancy over the locus. The conjecture follows from the existence of the flip for the contraction…

Algebraic Geometry · Mathematics 2016-09-07 V. V. Shokurov

In this article we present a 3-dimensional analogue of a well-known theorem of E. Bombieri (in 1973) which characterizes the bi-canonical birationality of surfaces of general type. Let $X$ be a projective minimal 3-fold of general type with…

Algebraic Geometry · Mathematics 2007-05-23 Meng Chen , De-Qi Zhang

We introduce the notion of boundary representation for fractal Fourier expansions, starting with a familiar notion of spectral pairs for affine fractal measures. Specializing to one dimension, we establish boundary representations for these…

Functional Analysis · Mathematics 2010-08-24 Dorin Ervin Dutkay , Palle E. T. Jorgensen

We consider all connected and simply connected 7-dimensional Lie groups whose Lie algebras have nilradical $\g_{5,2} = \s \{X_1, X_2, X_3, X_4, X_5 \colon [X_1, X_2] = X_4, [X_1, X_3] = X_5\}$ of Dixmier. First, we give a geometric…

Differential Geometry · Mathematics 2022-09-12 Tuyen T. M. Nguyen , Vu A. Le , Tuan A. Nguyen

In this article we prove the following boundedness result: Fix a DCC set $I\subset [0, 1]$. Let $\mathfrak{D}$ be the set of all log pairs $(X, \Delta)$ satisfying the following properties: (i) $X$ is a projective surface defined over an…

Algebraic Geometry · Mathematics 2020-11-10 Omprokash Das

Studying Manin's program for a family of spherical log Fano threefolds, we determine the asymptotic number of integral points whose height associated with an arbitrary ample line bundle is bounded. This confirms a recent conjecture by…

Number Theory · Mathematics 2025-05-16 Ulrich Derenthal , Florian Wilsch