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For a pair (X,L) consisting of a projective variety X over a perfect field of characteristic p>0 and an ample line bundle L on X, we introduce and study a positive characteristic analog of the $\alpha$-invariant introduced by Tian, which we…

Algebraic Geometry · Mathematics 2025-08-08 Suchitra Pande

We prove that the Fano variety of lines of a generic cubic fourfold containing a plane is isomorphic to a moduli space of twisted stable complexes on a K3 surface. On the other hand, we show that the Fano varieties are always birational to…

Algebraic Geometry · Mathematics 2011-12-26 Emanuele Macri , Paolo Stellari

We construct a geometrically compactified moduli algebraic space of Kahler-Einstein Fano manifolds.

Algebraic Geometry · Mathematics 2015-04-28 Yuji Odaka

It is shown that a complex normal projective variety has non-positive Kodaira dimension if it admits a non-isomorphic quasi-polarized endomorphism. The geometric structure of the variety is described by methods of equivariant lifting and…

Algebraic Geometry · Mathematics 2018-09-24 Noboru Nakayama , De-Qi Zhang

We endow the set of complements of a fixed subspace of a projective space with the structure of an affine space, and show that certain lines of such an affine space are affine reguli or cones over affine reguli. Moreover, we apply our…

Algebraic Geometry · Mathematics 2024-02-13 Andrea Blunck , Hans Havlicek

We derive explicit dimension formulas for irreducible $M_F$-spherical $K_F$-representations where $K_F$ is the maximal compact subgroup of the general linear group $GL(d,F)$ over a local field $F$ and $M_F$ is a closed subgroup of $K_F$…

Quantum Algebra · Mathematics 2007-05-23 Uri Onn , Jasper Stokman

Let $A$ be a unital $C^*$-algebra and $\alpha$ be an injective, unital endomorphism of $A$. A covariant representation of $(A,\alpha)$ is a pair $(\pi,T)$ consisting of a $C^*$-representation $\pi$ of $A$ on a Hilbert space $H$ and a…

Operator Algebras · Mathematics 2016-09-07 Paul S. Muhly , Baruch Solel

We introduce a model which allows the fine structure constant (alpha) to vary throughout space and time due to a coupling to a scalar field with a non-canonical kinetic structure. This provided a new extension of the…

General Relativity and Quantum Cosmology · Physics 2015-01-20 Alexander A. H. Graham

Let $X \subset \mathbb P(a_0,\ldots,a_n)$ be a quasi-smooth weighted Fano hypersurface of degree $d$ and index $I_X$ such that $a_i |d$ for all $i$, with $a_0 \le \ldots \le a_n$. If $I_X=1$, we show that, under a suitable condition, the…

Algebraic Geometry · Mathematics 2024-01-24 Taro Sano , Luca Tasin

This paper considers Q-Fano 3-folds X with \rho=1. The aim is to determine the maximal Fano index f of X. We prove that f<= 19, and that in case of equality, the Hilbert series of X equals that of weighted projective space PP(3,4,5,7). From…

Algebraic Geometry · Mathematics 2007-05-23 Kaori Suzuki

We construct several new families of Fano varieties of K3 type. We give a geometrical explanation of the K3 structure and we link some of them to projective families of irreducible holomorphic symplectic manifolds.

Algebraic Geometry · Mathematics 2019-04-12 Enrico Fatighenti , Giovanni Mongardi

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

We compute global log canonical thresholds of certain birationally bi-rigid Fano 3-folds embedded in weighted projective spaces as complete intersections of codimension 2 and prove that they admit an orbifold K\"{a}hler-Einstein metric and…

Algebraic Geometry · Mathematics 2019-03-19 In-Kyun Kim , Takuzo Okada , Joonyeong Won

We show that for every morphism f between nonsingular hypersurfaces of dimension at least 3 and of general type in projective space, there is an everywhere defined endomorphism F of projective space that restricts to f. As a corollary, we…

Algebraic Geometry · Mathematics 2007-05-23 David Sheppard

We show that any $n$-dimensional Fano manifold $X$ admitting K\"ahler-Einstein metrics satisfies that the anti-canonical volume is less than or equal to the value $(n+1)^n$. Moreover, the equality holds if and only if $X$ is isomorphic to…

Algebraic Geometry · Mathematics 2015-08-20 Kento Fujita

In this paper we define a numerical shape invariant of a continuous map called shape dimension of a map, which generalizes the shape dimension of a topological space. Some basic properties and applications of this invariant are given. The…

Algebraic Topology · Mathematics 2023-08-29 Pavel S. Gevorgyan , I. Pop

We establish an upper bound for the sectional genus of varieties which are invariant under Pfaff fields on projective spaces.

Algebraic Geometry · Mathematics 2011-02-14 Maurício Corrêa , Marcos Jardim

We show that Fano lattice polygons define a class of balanced quivers with interesting properties. The combinatorics of these quivers is related to singularities of the underlying toric Fano surface. This allows us to show that every Fano…

Algebraic Geometry · Mathematics 2019-07-23 Mohammad E. Akhtar

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

The quantum lens spaces form a natural and well-studied class of noncommutative spaces which can be subjected to classification using algebraic invariants by drawing on the fully developed classification theory of unital graph…

Operator Algebras · Mathematics 2025-01-30 Søren Eilers , Sophie Emma Zegers