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This is the second of a series of papers where we study the plurigenera, the Kodaira dimension and the Iitaka dimension on compact almost complex manifolds. By using the pseudoholomorphic pluricanonical map, we define the second version of…

Differential Geometry · Mathematics 2020-04-28 Haojie Chen , Weiyi Zhang

In this paper we investigate the Kodaira dimension of almost complex $4$-manifolds with torsion first Chern class. First, we prove that, if the almost complex structure is also tamed, the only possible values for the Kodaira dimension are…

Differential Geometry · Mathematics 2025-11-26 Lorenzo Sillari , Adriano Tomassini

We study the Kodaira dimension of almost complex manifolds admitting an $\mathrm{SU} (m)$-structure. We introduce the notion of almost complex structure of splitting type and of associated $\mathrm{SU} (m)$-structure. When the latter is…

Differential Geometry · Mathematics 2025-11-12 Lorenzo Sillari , Adriano Tomassini

The notion of Kodaira dimension has recently been extended to general almost complex manifolds. In this paper we focus on the Kodaira dimension of almost K\"ahler manifolds, providing an explicit computation for a family of almost K\"ahler…

Differential Geometry · Mathematics 2019-09-04 Andrea Cattaneo , Antonella Nannicini , Adriano Tomassini

This is the first of a series of papers, in which we study the plurigenera, the Kodaira dimension and more generally the Iitaka dimension on compact almost complex manifolds. Based on the Hodge theory on almost complex manifolds, we…

Differential Geometry · Mathematics 2020-04-28 Haojie Chen , Weiyi Zhang

In complex geometry a classical and useful invariant of a complex manifold is its Kodaira dimension. Since its introduction by Iitaka in the early 70's, its behavior under deformations was object of study and it is known that Kodaira…

Complex Variables · Mathematics 2023-07-27 Andrea Cattaneo

In this paper, we investigate Riemannian curvature constraints on the Kodaira dimension of compact almost Hermitian manifolds. Specifically, for a compact almost Hermitian manifold $(M, J, g)$ in the Gray-Hervella class…

Differential Geometry · Mathematics 2025-10-21 Xianchao Zhou

We study the space of closed anti-invariant forms on an almost complex manifold, possibly non compact. We construct families of (non integrable) almost complex structures on $\R^4$, such that the space of closed $J$-anti-invariant forms is…

Differential Geometry · Mathematics 2020-07-08 Richard Hind , Adriano Tomassini

We observed in our previous paper that all the complex structures on four-dimensional compact solvmanifolds, including tori, are left-invariant. In this paper we will give an example of a six-dimensional compact solvmanifold which admits a…

Complex Variables · Mathematics 2016-01-15 Keizo Hasegawa

We show that in every dimension greater than or equal to 4, there exist compact Kaehler manifolds which do not have the homotopy type of projective complex manifolds. Thus they a fortiori are not deformation equivalent to a projective…

Algebraic Geometry · Mathematics 2015-08-14 Claire Voisin

Not long ago, Cirici and Wilson defined a Dolbeault cohomology on almost complex manifolds to answer Hirzebruch's problem. In this paper, we define a refined Dolbeault cohomology on almost complex manifolds. We show that the condition…

Differential Geometry · Mathematics 2024-04-30 Dexie Lin

We consider three families of lattices on the oscillator group $G$, which is an almost nilpotent not completely solvable Lie group, giving rise to coverings $G \to M_{k, 0} \to M_{k, \pi} \to M_{k, \pi/2}$ for $k\in \Z$. We show that the…

Differential Geometry · Mathematics 2011-11-11 Sergio Console , Gabriela P. Ovando , Mauro Subils

This article mainly aims to overview the recent efforts on developing algebraic geometry for an arbitrary compact almost complex manifold. We review the results obtained by the guiding philosophy that a statement for smooth maps between…

Differential Geometry · Mathematics 2020-10-09 Weiyi Zhang

We study the Kodaira dimension of a real parallelizable manifold $M$, with an almost complex structure $J$ in standard form with respect to a given parallelism. For $X = (M, J)$ we give conditions under which $\operatorname{kod}(X) = 0$. We…

Differential Geometry · Mathematics 2023-07-26 Andrea Cattaneo , Antonella Nannicini , Adriano Tomassini

We define the Kodaira dimension for $3$-dimensional manifolds through Thurston's eight geometries, along with a classification in terms of this Kodaira dimension. We show this is compatible with other existing Kodaira dimensions and the…

Geometric Topology · Mathematics 2014-05-08 Weiyi Zhang

We give a characterization of almost abelian Lie groups carrying left invariant hypercomplex structures and we show that the corresponding Obata connection is always flat. We determine when such Lie groups admit HKT metrics and study the…

Differential Geometry · Mathematics 2023-04-26 Adrián Andrada , María Laura Barberis

In this paper we briefly survey the classical problem of understanding which Lie algebras admit a complex structure, put in the broader perspective of almost complex structures with special properties. We focus on the different behavior of…

Differential Geometry · Mathematics 2025-11-14 Lorenzo Sillari , Adriano Tomassini

We provide infinitely many examples of pairs of diffeomorphic, non simply connected K\" ahler manifolds of complex dimension three with different Kodaira dimensions. Also, in any possible Kodaira dimension we find infinitely many pairs of…

Differential Geometry · Mathematics 2007-05-23 Rares Rasdeaconu

We develop a spinorial description of CR structures of arbitrary codimension. More precisely, we characterize almost CR structures of arbitrary codimension on (Riemannian) manifolds by the existence of a Spin$^{c, r}$ structure carrying a…

Differential Geometry · Mathematics 2016-10-17 Rafael Herrera , Roger Nakad , Ivan Tellez

Generically an almost complex structure has no symmetries at all, but there exist symmetric structures. In this paper we describe how to guarantee that the pseudogroup of local symmetries is small (finite-dimensional). It will be indicated…

Differential Geometry · Mathematics 2013-11-19 Boris Kruglikov
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