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Zsolt Patakfalvi

Publications and source records attributed to Zsolt Patakfalvi.

At least 37 records · Page 2Linked to original sources
arXiv2018

Singularities of General Fibers and the LMMP

We use the theory of foliations to study the relative canonical divisor of a normalized inseparable base-change. Our main technical theorem states that it is linearly equivalent to a divisor with positive integer coefficients divisible by $p-1$. We deduce many consequences about the fibrations of the minimal model program: for example the general fibers of terminal $3$-fold Mori fiber spaces are normal in characteristic $p\geq 5$ and smooth in characteristic $p\geq 11$.

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arXiv2017

F-singularities in families

We study the behavior of test ideals and F-singularities in families. In particular, we obtain generic (and non-generic) restriction theorems for test ideals and non-F-pure ideals. Additionally, we study the global behavior of certain canonical linear systems (induced by Frobenius) associated to adjoint line bundles, in families. As a consequence, we obtain some positivity results for pushforwards of some adjoint line bundles and for certain subsheaves of these.

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arXiv2017

Birational characterization of abelian varieties and ordinary abelian varieties in characteristic p>0

Let $k$ be an algebraically closed field of characteristic $p>0$. We give a birational characterization of ordinary abelian varieties over $k$: a smooth projective variety $X$ is birational to an ordinary abelian variety if and only if $κ_S(X)=0$ and $b_1(X)=2 \dim X$. We also give a similar characterization of abelian varieties as well: a smooth projective variety $X$ is birational to an abelian variety if and only if $κ(X)=0$, and the Albanese morphism $a: X \to A$ is generically finite. Along the way, we also show that if $κ_S (X)=0$ (or if $κ(X)=0$ and $a$ is generically finite) then the Albanese morphism $a:X\to A$ is surjective and in particular $\dim A\leq \dim X$.

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arXiv2017

Positive characteristic algebraic geometry

These are notes for the Bootcamp volume for the 2015 AMS Summer Institute in Algebraic Geometry. They are based on earlier notes for the "Positive Characteristic Algebraic Geometry Workshop" held at University of Illinois at Chicago in March 2014.

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arXiv2016

Frobenius techniques in birational geometry

This is a survey for the 2015 AMS Summer Institute on Algebraic Geometry about the Frobenius type techniques recently used extensively in positive characteristic algebraic geometry. We first explain the basic ideas through simple versions of the fundamental definitions and statements, and then we survey most of the recent algebraic geometry results obtained using these techniques.

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arXiv2014

On subadditivity of Kodaira dimension in positive characteristic

We show that for a surjective, separable morphism f of smooth projective varieties over an algebraically closed field of positive characteristic such that $f_* \mathcal{O}_X = \mathcal{O}_Y$ subadditivity of Kodaira dimension holds, provided the base is of general type and the Hasse-Witt matrix of the geometric general fiber is not nilpotent.

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arXiv2014

Fibered stable varieties

We show that if a stable variety (in the sense of Kollár and Shepherd-Barron) admits a fibration with stable fibers and base, then this fibration structure deforms (uniquely) for all small deformations. During our proof we obtain also a Bogomolov-Sommese type vanishing for vector bundles and reflexive differential $n-1$-forms.

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arXiv2013

Arakelov-Parshin rigidity of towers of curve fibrations

Arakelov-Parshin rigidity is concerned with varieties mapping rigidly to the moduli stack M_h of canonically polarized manifolds. Affirmative answer for any class of maps implies finiteness of the given class. This article studies Arakelov-Parshin rigidity on an open subspace of M_h, on the locus KF_h of iterated Kodaira fibrations. First, we prove rigidity for all complete curves mapping finitely onto KF_h. Then, for generic affine curves mapping into KF_h, rigidity is shown when deg h =2. The method used in the latter part is showing that the iterated Kodaira-Spencer map is injective.

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arXiv2013

Depth of $F$-singularities and base change of relative canonical sheaves

For a characteristic $p > 0$ variety $X$ with controlled $F$-singularities, we state conditions which imply that a divisorial sheaf is Cohen-Macaulay or at least has depth $\geq 3$ at certain points. This mirrors results of Kollár for varieties in characteristic zero. As an application, we show that that relative canonical sheaves are compatible with arbitrary base change for certain families with sharply $F$-pure fibers.

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arXiv2012

Semi-positivity in positive characteristics

Let $f : (X, Δ) \to Y$ be a flat, projective family of sharply $F$-pure, log-canonically polarized pairs over an algebraically closed field of characteristic $p >0$ such that $p \nmid \ind(K_{X/Y} + Δ)$. We show that $K_{X/Y} + Δ$ is nef and that $f_* (\sO_X(m (K_{X/Y} + Δ)))$ is a nef vector bundle for $m \gg 0$ and divisible enough. Some of the results also extend to non log-canonically polarized pairs. The main motivation of the above results is projectivity of proper subspaces of the moduli space of stable pairs in positive characteristics. Other applications are Kodaira vanishing free, algebraic proofs of corresponding positivity results in characteristic zero, and special cases of subadditivity of Kodaira-dimension in positive characteristics.

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arXiv2012

Moduli of products of stable varieties

We study the moduli space of a product of stable varieties over the field of complex numbers, as defined via the minimal model program. Our main results are: (a) taking products gives a well-defined morphism from the product of moduli spaces of stable varieties to the moduli space of a product of stable varieties, (b) this map is always finite étale, and (c) this map very often is an isomorphism. Our results generalize and complete the work of Van Opstall in dimension 1. The local results rely on a study of the cotangent complex using some derived algebro-geometric methods, while the global ones use some differential-geometric input.

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