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We classify the terminal Fano threefolds of Picard number one that come with an effective action of a two-torus. Our approach applies also to higher dimensions and generalizes the correspondence between toric Fano varieties and lattice…

Algebraic Geometry · Mathematics 2025-07-08 Benjamin Bechtold , Elaine Huggenberger , Juergen Hausen , Michele Nicolussi

We classify the non-toric, $\mathbb Q$-factorial, Gorenstein, log terminal Fano threefolds of Picard number one that admit an effective action of a two-dimensional algebraic torus.

Algebraic Geometry · Mathematics 2022-11-17 Andreas Bäuerle , Jürgen Hausen

We announce a factorization result for equivariant birational morphisms between toric 4-folds whose source is Fano: such a morphism is always a composite of blow-ups along smooth invariant centers. Moreover, we show with a counterexample…

Algebraic Geometry · Mathematics 2007-05-23 Cinzia Casagrande

In this work we provide effective bounds and classification results for rational $\QQ$-factorial Fano varieties with a complexity-one torus action and Picard number one depending on the invariants dimension and Picard index. This…

Algebraic Geometry · Mathematics 2012-11-26 Elaine Herppich

We provide a systematic method to classify all smooth weak Fano toric varieties of Picard rank $3$ in any dimension using Macaulay2, and describe the classification explicitly in dimensions $3$ and $4$. There are $28$ and $114$ isomorphism…

Algebraic Geometry · Mathematics 2025-06-03 Zhengning Hu , Rohan Joshi

We generalized the construction of deformations of affine toric varieties of K. Altmann and our previous construction of deformations of weak Fano toric varieties to the case of arbitrary toric varieties by introducing the notion of…

Algebraic Geometry · Mathematics 2011-02-25 Anvar Mavlyutov

We investigate projective varieties which are geometric models of binary symmetric phylogenetic 3-valent trees. We prove that these varieties have Gorenstein terminal singularities (with small resolution) and they are Fano varieties of…

Algebraic Geometry · Mathematics 2007-05-23 Weronika Buczynska , Jaroslaw A. Wisniewski

We introduce a variety $\hat{G}_2$ parameterizing isotropic five-spaces of a general degenerate four-form in a seven dimensional vector space. It is in a natural way a degeneration of the variety $G_2$, the adjoint variety of the simple Lie…

Algebraic Geometry · Mathematics 2011-03-25 Michal Kapustka

We explicitly fully describe the K-moduli space of Fano threefold family number 3.3. We first show that K-semistable Fano varieties with volume greater than 18 are Gorenstein canonical and admit general elephants, decreasing the bound on a…

Algebraic Geometry · Mathematics 2025-10-16 Erroxe Etxabarri-Alberdi , James Matthew Jones , Theodoros Stylianos Papazachariou

A classical result of Bondal-Orlov states that a standard flip in birational geometry gives rise to a fully faithful functor between derived categories of coherent sheaves. We complete their embedding into a semiorthogonal decomposition by…

Algebraic Geometry · Mathematics 2023-02-22 Pieter Belmans , Lie Fu , Theo Raedschelders

We introduce the notion of intrinsic Grassmannians which generalizes the well known weighted Grassmannians. An intrinsic Grassmannian is a normal projective variety whose Cox ring is defined by the Pl\"ucker ideal $I_{d,n}$ of the…

Algebraic Geometry · Mathematics 2020-12-15 Muhammad Imran Qureshi , Milena Wrobel

We classify Fano 3-folds with canonical Gorenstein singularities whose anticanonical linear system has no base points but does not give an embedding, and we classify anticanonically embedded Fano 3-folds with canonical Gorenstein…

Algebraic Geometry · Mathematics 2007-05-23 Ivan Cheltsov , Constantin Shramov , Victor Przyjalkowski

A dissection of a polygon is obtained by drawing diagonals such that no two diagonals intersect in their interiors. In this paper, we define a toric variety of Schr\"{o}der type as a smooth toric variety associated with a polygon…

Algebraic Geometry · Mathematics 2022-04-04 JiSun Huh , Seonjeong Park

A conjecture of Pukhlikov states that a smooth Fano variety of dimension at least four and index one is birationally rigid. We show that a general member of the linear system given by the ample generator of the Picard group of the moduli…

Algebraic Geometry · Mathematics 2007-05-23 Ana-Maria Castravet

Let $X$ be a complex smooth Fano variety of dimension $n$. In this paper, we give a classification of such $X$ when the pseudoindex is equal to $\dfrac{\dim X+1}{2}$ and the Picard number greater than one.

Algebraic Geometry · Mathematics 2024-09-23 Kiwamu Watanabe

The toric variety of a matroid is projectively normal, and therefore it is Cohen-Macaulay. We provide a complete graph-theoretic classification when the toric variety of a graphic matroid is Gorenstein.

Combinatorics · Mathematics 2021-11-30 Takayuki Hibi , Michał Lasoń , Kazunori Matsuda , Mateusz Michałek , Martin Vodička

It is known that every integral convex polytope is unimodularly equivalent to a face of some Gorenstein Fano polytope. It is then reasonable to ask whether every normal polytope is unimodularly equivalent to a face of some normal Gorenstein…

Combinatorics · Mathematics 2020-09-08 Takayuki Hibi , Akiyoshi Tsuchiya

We show that the optimal upper bound for the anticanonical degrees of non-Gorenstein $\mathbb{Q}$-factorial canonical Fano threefolds with Picard number one is 200/3.

Algebraic Geometry · Mathematics 2026-01-21 Minyou Li

We classify all complete non-singular toric varieties with Picard number four via a combinatorial framework based on fanlike simplicial spheres and characteristic maps. This classification yields $59$ fanlike seeds with Picard number four,…

Algebraic Geometry · Mathematics 2025-04-28 Suyoung Choi , Hyeontae Jang , Mathieu Vallée

We develop pivotal and spherical versions of graded extension theory. We define the corresponding analogues of Brauer-Picard $2$-categorical groups and realize them as fixed points of natural $\mathbb{Z}$ and $\mathbb{Z}/2\mathbb{Z}$…