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We consider a proper flat fibration with real base and complex fibers. First we construct odd characteristic classes for such fibrations by a method that generalizes constructions of Bismut-Lott. Then we consider the direct image of a…

Differential Geometry · Mathematics 2017-02-16 Yeping Zhang

We give an intrinsic definition of (affine very) special real manifolds and realise any such manifold $M$ as a domain in affine space equipped with a metric which is the Hessian of a cubic polynomial. We prove that the tangent bundle $N=TM$…

Differential Geometry · Mathematics 2009-01-06 Dmitri V. Alekseevsky , Vicente Cortés

A hypercomplex manifold is by definition a smooth manifold equipped with two anticommuting integrable almost complex structures. For example, every hyperkaehler manifold is canonically hypercomplex (the converse is not true). For every…

alg-geom · Mathematics 2008-02-03 D. Kaledin

We study extensions of Wermer's maximality theorem to several complex variables. We exhibit various smoothly embedded manifolds in complex Euclidean space whose hulls are non-trivial but contain no analytic disks. We answer a question posed…

Complex Variables · Mathematics 2017-07-05 Alexander J. Izzo , Håkan Samuelsson Kalm , Erlend Fornæss Wold

Let X be a compact Kaehler manifold. We expect that any direct sum decomposition of the tangent bundle T(X) comes from a splitting of the universal covering space of X as a product of manifolds, in such a way that the given decomposition of…

Algebraic Geometry · Mathematics 2007-05-23 Arnaud Beauville

We study conformal tractor bundles from an extrinsic viewpoint, relating them to codimension two spacelike immersions into Lorentzian manifolds. We show that, at least locally, every Riemannian conformal structure admits a natural…

Differential Geometry · Mathematics 2026-02-05 Rodrigo Morón

We study the existence of generalized complex structures on the six-dimensional sphere $\mathbb S^6$. We work with the generalized tangent bundle $\mathbb T\mathbb S^6\to \mathbb S^6$ and define the integrability of generalized geometric…

Differential Geometry · Mathematics 2025-07-22 Fernando Etayo , Pablo Gómez-Nicolás , Rafael Santamaría

We compute the tensor triangular spectrum of perfect complexes of filtered modules over a commutative ring, and deduce a classification of the thick tensor ideals. We give two proofs: one by reducing to perfect complexes of graded modules…

Category Theory · Mathematics 2019-09-11 Martin Gallauer

Below, by space we mean a separable metrizable zero-dimensional space. It is studied when the space can be embedded in a Cantor set while maintaining the algebraic structure. Main results of the work: every space is an open retract of a…

General Topology · Mathematics 2023-06-13 Evgenii Reznichenko

A tropical expansion is a degeneration of a toroidal embedding, induced by a polyhedral subdivision of its tropicalisation. Each irreducible component of a tropical expansion admits a collapsing map down to a stratum of the original…

Algebraic Geometry · Mathematics 2025-11-21 Francesca Carocci , Navid Nabijou

When two smooth manifold bundles over the same base are fiberwise tangentially homeomorphic, the difference is measured by a homology class in the total space of the bundle. We call this the relative smooth structure class. Rationally and…

K-Theory and Homology · Mathematics 2012-04-10 Sebastian Goette , Kiyoshi Igusa , Bruce Williams

We show that an analogue of the Ball-Box Theorem for step 2, completely non-integrable bundles from smooth sub-Riemannian geometry hold true for a class of non-differentiable tangent subbundles that satisfy a geometric condition. In the…

Differential Geometry · Mathematics 2016-10-05 Sina Türeli

Given a complex manifold $X$, any K\"ahler class defines an affine bundle over $X$, and any K\"ahler form in the given class defines a totally real embedding of $X$ into this affine bundle. We formulate conditions under which the affine…

Complex Variables · Mathematics 2020-06-18 Daniel Greb , Michael Lennox Wong

This is a review of the basic concepts of the theory of real and complex smooth vector bundles with finite rank. Besides, the concept of a tensor field is studied within the general framework of a smooth vector bundle rather than a smooth…

General Mathematics · Mathematics 2022-01-25 Farzad Shahi

The works of Commichau--Grauert and Hirschowitz showed that a formal equivalence between embeddings of a compact complex manifold is convergent, if the embeddings have sufficiently positive normal bundles in a suitable sense. We show that…

Differential Geometry · Mathematics 2024-08-29 Jaehyun Hong , Jun-Muk Hwang

We study almost complex structures with lower bounds on the rank of the Nijenhuis tensor. Namely, we show that they satisfy an $h$-principle. As a consequence, all parallelizable manifolds and all manifolds of dimension $2n\geq 10$…

Differential Geometry · Mathematics 2022-10-04 Rui Coelho , Giovanni Placini , Jonas Stelzig

We consider manifolds equipped with a foliation $\cal F$ of codimension $4q$, and an almost quaternionic structure $Q$ on the transversal bundle of ${\cal F}$. After discussing conditions of projectability and integrability of $Q$, we study…

Differential Geometry · Mathematics 2007-05-23 Paolo Piccinni , Izu Vaisman

This paper contains a long summary of the basic properties of higher FR torsion. An attempt is made to simplify the constructions from my book Higher Franz-Reidemeister Torsion (IP/AMS Studies in Advanced Math 31). Some new basic theorems…

K-Theory and Homology · Mathematics 2007-05-23 Kiyoshi Igusa

In this paper, we prove that a compact K\"ahler manifold $X$ with pseudo-effective (resp. singular positively curved) tangent bundle admits a smooth (resp. locally constant) rationally connected fibration $\phi \colon X \to Y$ onto a finite…

Algebraic Geometry · Mathematics 2025-02-04 Shin-ichi Matsumura , Chenghao Qing

We give new sufficient conditions for the integrability and unique integrability of continuous tangent sub-bundles on manifolds of arbitrary dimension, generalizing Frobenius' classical Theorem for C^1 sub-bundles. Using these conditions we…

Classical Analysis and ODEs · Mathematics 2016-10-11 Stefano Luzzatto , Sina Tureli , Khadim War