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The Chow-Mumford (CM) line bundle is a functorial line bundle on the base of any family of klt Fano varieties. It is conjectured that it yields a polarization on the moduli space of K-poly-stable klt Fano varieties. Proving ampleness of the…

Algebraic Geometry · Mathematics 2020-09-01 Giulio Codogni , Zsolt Patakfalvi

In this short note, we give an alternative proof of the semipositivity of the Chow-Mumford line bundle for families of K-semistable log-Fano pairs, and of the nefness threeshold for the log-anti-canonical line bundle on families of K-stable…

Algebraic Geometry · Mathematics 2023-07-14 Giulio Codogni , Zsolt Patakfalvi

In this paper, we consider the CM line bundle on the K-moduli space, i.e., the moduli space parametrizing K-polystable Fano varieties. We prove it is ample on any proper subspace parametrizing reduced uniformly K-stable Fano varieties which…

Algebraic Geometry · Mathematics 2021-02-22 Chenyang Xu , Ziquan Zhuang

We show that the CM line bundle on a proper family parametrizing specially K-stable varieties with maximal variation is ample. As an application, we show projectivity of any proper subspace of the coarse moduli space of uniformly…

Algebraic Geometry · Mathematics 2023-10-10 Masafumi Hattori

We prove that the degree of the CM line bundle for a normal family over a curve with fixed general fibers is strictly minimized if the special fiber is either a smooth projective manifold with a unique cscK metric or ``specially K-stable",…

Algebraic Geometry · Mathematics 2022-11-08 Masafumi Hattori

We apply the theory of the Chow-Mumford line bundle as developed by Arezzo-et-al and build on earlier key insights of Paul and Tian (see \cite{Arezzo:DellaVedova:LaNave} and the references therein). In particular, we give an explicit…

Algebraic Geometry · Mathematics 2025-09-23 Nathan Grieve

We prove that K-polystable degenerations of Q-Fano varieties are unique. Furthermore, we show that the moduli stack of K-stable Q-Fano varieties is separated. Together with [Jia17,BL18], the latter result yields a separated Deligne-Mumford…

Algebraic Geometry · Mathematics 2019-07-10 Harold Blum , Chenyang Xu

We prove new boundedness results across different areas of algebraic geometry, stemming from a unifying technical starting point: bounding the integer $q > 0$ such that the $q$-th Hodge bundle becomes (semi-)positive for families of stable…

Algebraic Geometry · Mathematics 2025-08-04 Giulio Codogni , Zsolt Patakfalvi , Luca Tasin

The 'moduli continuity method' permits an explicit algebraisation of the Gromov-Hausdorff compactification of K\"ahler-Einstein metrics on Fano manifolds in some fundamental examples. In this paper, we apply such method in the 'log setting'…

Algebraic Geometry · Mathematics 2020-11-11 Patricio Gallardo , Jesus Martinez-Garcia , Cristiano Spotti

We give a lower bound of the $\delta$-invariants of ample line bundles in terms of Seshadri constants. As applications, we prove the uniform K-stability of infinitely many families of Fano hypersurfaces of arbitrarily large index, as well…

Algebraic Geometry · Mathematics 2022-04-28 Hamid Abban , Ziquan Zhuang

We show that positivity of the CM line associated to a family of polarised varieties is intimately related to the stability of its members. We prove that the CM line is nef on any curve which meets the stable locus, and that it is…

Algebraic Geometry · Mathematics 2017-03-24 J. Fine , J. Ross

We study strong exceptional collections of line bundles on Fano toric Deligne-Mumford stacks $\mathbb{P}_{\mathbf{\Sigma}}$ with rank of Picard group at most two. We prove that any strong exceptional collection of line bundles generates the…

Algebraic Geometry · Mathematics 2019-07-17 Lev Borisov , Chengxi Wang

For any flat projective family $(\mX,\mL)\rightarrow C$ such that the generic fibre $\mX_\eta$ is a klt Q-Fano variety and $\mL|_{\mX_\eta}\sim_{Q}-K_{X_{\eta}}$, we use the techniques from the minimal model program (MMP) to modify the…

Algebraic Geometry · Mathematics 2013-10-15 Chi Li , Chenyang Xu

We prove several boundedness results for log Fano pairs with certain K-stability. In particular, we prove that K-semistable log Fano pairs of Maeda type form a log bounded family. We also compute K-semistable domains for some examples.

Algebraic Geometry · Mathematics 2025-01-07 Konstantin Loginov , Chuyu Zhou

We show that if $X$ is an abelian variety of dimension $g \geq 1$ and ${\mathcal E}$ is an M-regular coherent sheaf on $X$, the Castelnuovo-Mumford regularity of ${\mathcal E}$ with respect to an ample and globally generated line bundle…

Algebraic Geometry · Mathematics 2017-10-10 Alex Küronya , Yusuf Mustopa

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

In this paper, we develop an algebraic K-stability theory (e.g. special test configuration theory and optimal destabilization theory) for log Fano $\mathbb R$-pairs, and construct a proper K-moduli space to parametrize K-polystable log Fano…

Algebraic Geometry · Mathematics 2024-12-23 Yuchen Liu , Chuyu Zhou

We introduce a theory of uniform K-stability for big line bundles on smooth projective varieties. This extends the existing theory both for varieties with ample line bundles, and for varieties with big anticanonical class. Our main result…

Algebraic Geometry · Mathematics 2026-03-27 Ruadhaí Dervan , Rémi Reboulet

This paper is concerned with a sufficient criterion to guarantee that a given foliation on a normal variety has algebraic and rationally connected leaves. Following ideas from a preprint of Bogomolov-McQuillan and using recent works of…

Algebraic Geometry · Mathematics 2009-09-29 Stefan Kebekus , Luis Sola Conde , Matei Toma

We investigate the K-stability of certain blow-ups of $\mathbb{P}^1$-bundles over a Fano variety $V$, where the $\mathbb{P}^1$-bundle is the projective compactification of a line bundle $L$ proportional to $-K_V$ and the center of the…

Algebraic Geometry · Mathematics 2024-12-17 Daniel Mallory
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