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In this paper we investigate various properties of generalised pairs in families, especially boundedness of several kinds. We show that many statements for usual pairs do not hold for generalised pairs. In particular, we construct an…

Algebraic Geometry · Mathematics 2022-04-25 Caucher Birkar , Christopher D. Hacon

Up to finite \'etale cover, any smooth complex projective variety $X$ with nef anti-canonical bundle is a holomorphic fibre bundle over a $K$-trivial variety with locally constant transition functions. We show that this result is optimal by…

Algebraic Geometry · Mathematics 2025-03-26 Niklas Müller

The effective freeness in Fujita's conjecture states that, for an ample line bundle $L$ on a complex projective manifold $X$, the adjoint bundle $K_X\otimes L^{\otimes m}$ is globally generated when $m \geq \dim_{\mathbb C} X + 1$.…

Algebraic Geometry · Mathematics 2024-11-26 Tsz On Mario Chan

In this note, we extend the theories of the canonical bundle formula and adjunction to the case of generalized pairs. As an application, we study a particular case of a conjecture by Prokhorov and Shokurov.

Algebraic Geometry · Mathematics 2021-08-12 Stefano Filipazzi

Over an algebraically closed field $\mathbb{K}$ with any characteristic, on an $N$-dimensional smooth projective $\mathbb{K}$-variety $\mathbf{P}$ equipped with $c\geqslant N/2$ very ample line bundles $\mathcal{L}_1,\dots,\mathcal{L}_c$,…

Algebraic Geometry · Mathematics 2016-01-21 Song-Yan Xie

The generalized $k$-connectivity of a graph $G$, denoted by $\kappa_k(G)$, is a generalization of the traditional connectivity. It is well known that the generalized $k$-connectivity is an important indicator for measuring the fault…

Combinatorics · Mathematics 2021-04-26 Wang Jing , Li Fangmin

Let $(X,B)$ be a log canonical pair over a normal variety $Z$ with maximal Albanese dimension. If $K_X+B$ is relatively abundant over $Z$ (for example, $K_X+B$ is relatively big over $Z$), then we prove that $K_X+B$ is abundant. In…

Algebraic Geometry · Mathematics 2018-05-29 Zhengyu Hu

The aim of this survey paper is threefold: (a) to discuss the status of the Morrison-Kawamata cone conjecture, (b) to report on recent developments towards the Abundance Conjecture, and (c) to discuss the nef line bundle version of the…

Algebraic Geometry · Mathematics 2019-04-15 Vladimir Lazić , Keiji Oguiso , Thomas Peternell

We will show that the sequence appearing in the double recurrence theorem is a good universal weight for the Furstenberg averages. That is, given a system $(X, \mathcal{F}, \mu, T)$ and bounded functions $f_1, f_2 \in L^\infty(\mu)$, there…

Dynamical Systems · Mathematics 2016-01-06 Idris Assani , Ryo Moore

Generalising a classical theorem by Ueno, we prove structure results for manifolds with nef or semiample cotangent bundle.

Algebraic Geometry · Mathematics 2017-11-07 Andreas Höring

Let $(X,B)$ be a pair, and let $f \colon X \rightarrow S$ be a contraction with $-(K_X + B)$ nef over $S$. A conjecture, known as the Shokurov-Koll\'{a}r connectedness principle, predicts that $f^{-1} (s) \cap \mathrm{Nklt}(X,B)$ has at…

Algebraic Geometry · Mathematics 2023-04-25 Stefano Filipazzi , Roberto Svaldi

We develop a theory of $P$-trivial MMP whose each step is $P$-trivial for a given nef divisor $P$. As an application, we prove that, given a projective generalised klt pair $(X,B+M)$ with data $M'$ being just a nef $\mathbb{R}$-divisor, if…

Algebraic Geometry · Mathematics 2025-01-14 Zhengyu Hu

We prove the bulk universality of the $\beta$-ensembles with non-convex regular analytic potentials for any $\beta>0$. This removes the convexity assumption appeared in our earlier work. The convexity condition enabled us to use the…

Probability · Mathematics 2015-06-03 Paul Bourgade , Laszlo Erdos , Horng-Tzer Yau

We give a generalization of Collatz conjecture or 3n+1 problem on 2-adic completion of Q. A isometric of $Q_2$ provides information on the average behavior of the firsts terms of the sequence according to the class of $u_0$ modulo $2^m$. A…

Number Theory · Mathematics 2016-07-11 Vincent Fleckinger , Ibrahim Abdoulkarim

The main geometric result of this paper is that given any family of surfaces of general type f:X-->B, for sufficiently large n the fiber product X^n_B dominates a variety of general type. This result is especially interesting when it is…

alg-geom · Mathematics 2008-02-03 Brendan Hassett

The notes start with an elementary introduction to a few important analytic techniques of algebraic geometry: closed positive currents, $L^2$ estimates for the $\dbar$-operator on positive vector bundles, Nadel's vanishing theorem for…

alg-geom · Mathematics 2015-06-30 Jean-Pierre Demailly

We formulate a generalization of the volume conjecture for planar graphs. Denoting by <G, c> the Kauffman bracket of the graph G whose edges are decorated by real "colors" c, the conjecture states that, under suitable conditions, certain…

Geometric Topology · Mathematics 2014-03-11 Francesco Costantino , François Guéritaud , Roland van der Veen

We observe what the canonical bundle formula gives towards a conjecture of Schnell on algebraic fiber spaces, a question concerning the equivalence between the non-vanishing conjecture and the Campana--Peternell conjecture. As a result, we…

Algebraic Geometry · Mathematics 2025-10-09 Hyunsuk Kim

Given a fibration $f$ between two projective manifolds $X$ and $Y$, we provide a sufficient condition such that the direct images $f_{\ast}(K_{X/Y}\otimes L\otimes\mathscr{I}(f,\|L\|))$ is nef, where $L$ is a holomorphic line bundle with…

Algebraic Geometry · Mathematics 2021-08-10 Jingcao Wu

Let $\overline{\mathrm{Mov}}^k(X)$ be the closure of the cone $\mathrm{Mov}^k(X)$ generated by classes of effective divisors on a projective variety $X$ with stable base locus of codimension at least $k+1$. We propose a generalized version…

Algebraic Geometry · Mathematics 2024-05-24 Gilberto Bini , Maria Chiara Brambilla , Claudio Fontanari , Elisa Postinghel