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In this short article we provide a proof of the Iitaka conjecture for algebraic fiber spaces over abelian varieties.

Algebraic Geometry · Mathematics 2016-08-04 Junyan Cao , Mihai Paun

We study the behavior of the Kodaira dimension of algebraic fiber spaces over threefolds. We prove some cases of the Iitaka Conjecture $C_{n,3}$, including certain situations where the base variety is a Calabi--Yau threefold.

Algebraic Geometry · Mathematics 2026-05-12 Houari Benammar Ammar

The main purpose of this paper is to prove the Iitaka conjecture $C_{n,m}$ on the assumption that the sufficiently general fibers have maximal Albanese dimension.

Algebraic Geometry · Mathematics 2007-05-23 Osamu Fujino

We prove that the Iitaka conjecture $C_{n,m}$ for algebraic fibre spaces holds up to dimension 6, that is, when $n\le 6$.

Algebraic Geometry · Mathematics 2008-06-30 Caucher Birkar

We prove an additivity result for the log Kodaira dimension of algebraic fiber spaces over abelian varieties, a superadditivity result for fiber spaces over varieties of maximal Albanese dimension, as well as a subadditivity result for log…

Algebraic Geometry · Mathematics 2024-07-24 Fanjun Meng , Mihnea Popa

Let \( f: X \to Y \) be an algebraic fiber space, where \( X \) and \( Y \) are smooth projective varieties of dimensions \( n \) and \( m \), respectively. In \cite{Caopaun}, Cao and P\u{a}un proved \( C_{n,m} \) when \( Y \) has maximal…

Algebraic Geometry · Mathematics 2025-12-15 Houari Benammar Ammar

Let $S \to C$ be a Kodaira fibration. Here we show that whether or not the algebraic surface $S$ is defined over a number field depends only on the biholomorphic class of its universal cover.

Algebraic Geometry · Mathematics 2018-08-03 Gabino González-Diez , Sebastián Reyes-Carocca

We present a simplified proof for a recent theorem by Junyan Cao and Mihai Paun, confirming a special case of Iitaka's conjecture: if $f \colon X\to Y$ is an algebraic fiber space, and if the Albanese mapping of $Y$ is generically finite…

Algebraic Geometry · Mathematics 2017-05-11 Christopher Hacon , Mihnea Popa , Christian Schnell

We prove Iitaka's $C_{n,m}$ conjecture for $3$-folds over the algebraic closure of finite fields. Along the way we prove some results on the birational geometry of log surfaces over nonclosed fields and apply these to existence of relative…

Algebraic Geometry · Mathematics 2015-09-01 Caucher Birkar , Yifei Chen , Lei Zhang

The purpose of this paper is to establish a subadditivity theorem of Okounkov bodies for algebraic fiber spaces. As applications, we obtain a product formula of the restricted canonical volumes for algebraic fiber spaces and a sufficient…

Algebraic Geometry · Mathematics 2021-11-03 Sung Rak Choi , Jinhyung Park

In this paper, we prove a positive characteristic analog of Nakayama's inequality on the numerical Kodaira dimension of algebraic fiber spaces when the generic fibers have nef canonical divisors. To this end, we establish variants of Popa…

Algebraic Geometry · Mathematics 2023-05-16 Sho Ejiri

In this paper, we prove that for a fibration $f:X\to Z$ from a smooth projective 3-fold to a smooth projective curve, over an algebraically closed field $k$ with $\mathrm{char} k =p >5$, if the geometric generic fiber $X_{\overline\eta}$ is…

Algebraic Geometry · Mathematics 2018-06-26 Sho Ejiri , Lei Zhang

In this paper, we collect basic properties of the Albanese dimension and explain how to generalize the main theorem of [F2](math.AG/0204262). This paper is a supplement and a generalization of [F2]. We also prove an inequality of…

Algebraic Geometry · Mathematics 2007-05-23 Osamu Fujino

In this paper, we study the descent of positivity of the canonical bundle along fiber spaces. As a consequence, we prove a conjecture of Schnell, establishing the equivalence between the Non-vanishing Conjecture and its generalized version…

Algebraic Geometry · Mathematics 2025-12-23 Yongpan Zou

In this paper, we prove the non-vanishing conjecture for cotangent bundles on isotrivial elliptic surfaces. Combined with the result by H\"{o}ring and Peternell, it completely solves the question for surfaces with Kodaira dimension at most…

Algebraic Geometry · Mathematics 2025-01-24 Haesong Seo

We show that if $X$ is a smooth complex projective variety with Kodaira dimension $0$ then the Kodaira dimension of a general fiber of its Albanese map is at most $h^0(\Omega ^1 _X)$.

Algebraic Geometry · Mathematics 2008-02-08 Jungkai A. Chen , Christopher D. Hacon

We consider the multicanonical systems $\vert mK_{S}\vert$ of quasi-elliptic surfaces with Kodaira dimension $1$ in characteristic 2. We show that for any $m \geq 6$ $\vert mK_{S}\vert$ gives the structure of quasi-elliptic fiber space, and…

Algebraic Geometry · Mathematics 2020-06-23 Toshiyuki Katsura , Natsuo Saito

We explore the relationship between fibrations arising naturally from a surjective morphism to an abelian variety. These fibrations encode geometric information about the morphism. Our study focuses on the interplay of these fibrations and…

Algebraic Geometry · Mathematics 2024-07-24 Fanjun Meng

We show that the general fibres of the Albanese morphism of a projective special manifold are special as well (a question raised by the first-named author). The main ingredient of the proof is a version (established by Birkar and Chen) with…

Algebraic Geometry · Mathematics 2014-12-09 Frédéric Campana , Benoît Claudon

Let $f:X\to Y$ be an algebraic fiber space with general fiber $F$. If $Y$ is of maximal Albanese dimension, we show that $\kappa (X)\geq \kappa (Y)+\kappa (F)$.

Algebraic Geometry · Mathematics 2015-05-19 Jungkai Alfred Chen , Christopher D. Hacon
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