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Let $X$ be an $n$-dimensional smooth complex projective variety embedded in $\mathbb{C}\mathbb{P}^{N}$. We construct a smooth family $\mathcal{X}$ over $\mathbb{C}$ with an embedding in $\mathbb{C}\mathbb{P}^{N} \times \mathbb{C}$ whose…

Symplectic Geometry · Mathematics 2018-09-26 Kiumars Kaveh

We show that some important classes of weak Fano $3$-folds of Picard rank $2$ do not satisfy Bott vanishing. Using this we show that any smooth projective $3$-fold $X$ of Picard rank $2$ with $-K_X$ nef which is the image of a projective…

Algebraic Geometry · Mathematics 2025-09-05 Supravat Sarkar

We first give a relative flexible process to construct torsion cohomology classes for Shimura varieties of Kottwitz-Harris-Taylor type with coefficient in a non too regular local system. We then prove that associated to each torsion…

Number Theory · Mathematics 2017-01-03 Pascal Boyer

We calculate the automorphism group of a complete toric variety $X$ with torus $T_M$. We prove that the radical unipotent of $Aut_k^0X$ is a semidirect product of additive groups, the reductive part is a quotient of a product of lineal…

Algebraic Geometry · Mathematics 2018-09-25 M. T Sancho , J. P Moreno , Carlos Sancho

A quasitoric manifold $M$ is a $2n$-dimensional manifold which admits an action of an $n$-dimensional torus which has some nice properties. We determine the isomorphism type of a maximal compact connected Lie-subgroup $G$ of…

Geometric Topology · Mathematics 2015-11-05 Michael Wiemeler

By the classical result of Milnor and Novikov, the unitary cobordism ring is isomorphic to a graded polynomial ring with countably many generators: $\Omega^U_*\simeq \mathbb Z[a_1,a_2,\dots]$, ${\rm deg}(a_i)=2i$. In this paper we solve a…

Algebraic Topology · Mathematics 2017-05-23 Yury Ustinovskiy , Grigory Solomadin

We prove LeBrun--Salamon conjecture in the following situation: if $X$ is a contact Fano manifold of dimension $2n+1$ whose group of automorphisms is reductive of rank $\geq \max(2,(n-3)/2)$ then $X$ is the adjoint variety of a simple…

Algebraic Geometry · Mathematics 2021-03-15 Gianluca Occhetta , Eleonora A. Romano , Luis E. Solá Conde , Jarosław A. Wiśniewski

To any graph $G$ one can associate a toric variety $X(\mathcal{P}G)$, obtained as a blowup of projective space along coordinate subspaces corresponding to connected subgraphs of $G$. The polytope of this toric variety is the graph…

Algebraic Geometry · Mathematics 2017-06-06 Rodrigo Ferreira da Rosa , David Jensen , Dhruv Ranganathan

Q-Gorenstein toric contact manifolds provide an interesting class of examples of contact manifolds with torsion first Chern class. They are completely determined by certain rational convex polytopes, called toric diagrams, and arise both as…

Symplectic Geometry · Mathematics 2023-06-16 Miguel Abreu , Leonardo Macarini , Miguel Moreira

Let $X$ be a compact complex manifold such that its canonical bundle $K_X$ is numerically trivial. Assume additionally that $X$ is Moishezon or $X$ is Fujiki with dimension at most four. Using the MMP and classical results in foliation…

Differential Geometry · Mathematics 2024-09-11 Indranil Biswas , Junyan Cao , Sorin Dumitrescu , Henri Guenancia

We introduce an analogue of the Novikov Conjecture on higher signatures in the context of the algebraic geometry of (nonsingular) complex projective varieties. This conjecture asserts that certain "higher Todd genera" are birational…

Algebraic Geometry · Mathematics 2011-03-10 Jonathan Rosenberg

Toric orbifolds are a generalization of simplicial projective toric varieties. In this paper, we show that there is a resolution of singularities of a toric orbifold. In a different category, the class of quasi-contact toric manifolds…

Algebraic Topology · Mathematics 2022-08-23 Koushik Brahma , Soumen Sarkar , Subhankar Sau

We show that the theory of stable complex $G$-cobordisms, for a torus $G$, is embedded into the theory of stable complex $G$-cobordisms of not necessarily compact manifolds equipped with proper abstract moment maps. Thus the introduction of…

Differential Geometry · Mathematics 2007-05-23 Viktor L. Ginzburg , Victor L. Guillemin , Yael Karshon

A compact solvmanifold of completely solvable type, i.e. a compact quotient of a completely solvable Lie group by a lattice, has a K\"ahler structure if and only if it is a complex torus. We show more in general that a compact solvmanifold…

Differential Geometry · Mathematics 2015-05-12 Anna Fino , Hisashi Kasuya

We study the cohomological rigidity problem of two families of manifolds with torus actions: the so-called moment-angle manifolds, whose study is linked with combinatorial geometry and combinatorial commutative algebra; and topological…

Algebraic Topology · Mathematics 2024-10-29 Feifei Fan , Jun Ma , Xiangjun Wang

For a complete toric variety, we obtain an explicit formula for the localized equivariant Todd class in terms of the combinatorial data -- the fan. This is based on the equivariant Riemann-Roch theorem and the computation of the equivariant…

Algebraic Geometry · Mathematics 2007-05-23 Jean-Luc Brylinski , Bin Zhang

Motivated by work of Fine and Panov, and of Lindsay and Panov, we prove that every closed symplectic complexity one space that is positive (e.g. positive monotone) enjoys topological properties that Fano varieties with a complexity one…

Symplectic Geometry · Mathematics 2019-05-31 Silvia Sabatini , Daniele Sepe

In dimension 4, we extend the correspondence between compact nonsingular toric varieties and regular fans to a correspondence between almost complex torus manifolds and families of multi-fans in a geometric way, where an (almost) complex…

Differential Geometry · Mathematics 2025-04-25 Donghoon Jang

For an equivariantly formal action of a compact torus $T$ on a smooth manifold $X$ with isolated fixed points we investigate the global homological properties of the graded poset $S(X)$ of face submanifolds. We prove that the condition of…

Algebraic Topology · Mathematics 2026-02-10 Anton Ayzenberg , Mikiya Masuda , Grigory Solomadin

In the focus of our paper is a system of axioms that serves as a basis for introducing structural data for $(2n,k)$-manifolds $M^{2n}$, where $M^{2n}$ is a smooth, compact $2n$-dimensional manifold with a smooth effective action of the…

Algebraic Topology · Mathematics 2019-09-04 Victor M. Buchstaber , Svjetlana Terzic