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We classify invariant almost complex structures on homogeneous manifolds of dimension 6 with semi-simple isotropy. Those with non-degenerate Nijenhuis tensor have the automorphism group of dimension either 14 or 9. An invariant almost…

Differential Geometry · Mathematics 2014-02-13 Dmitri V. Alekseevsky , Boris Kruglikov , Henrik Winther

The isometry group of a compact n-dimensional hyperbolic manifold is known to be finite. We show that for every n > 2, every finite group is realized as the full isometry group of some compact hyperbolic n-manifold. The cases n = 2 and n =…

Group Theory · Mathematics 2009-11-10 M. Belolipetsky , A. Lubotzky

We prove that in dimensions not equal to 4, 5, or 7, the homology and homotopy groups of the classifying space of the topological group of diffeomorphisms of a disk fixing the boundary are finitely generated in each degree. The proof uses…

Algebraic Topology · Mathematics 2019-10-23 Alexander Kupers

We classify the non-degenerate homogeneous hypersurfaces in real and complex affine four-space whose symmetry group is at least four-dimensional.

Differential Geometry · Mathematics 2007-05-23 Michael Eastwood , Vladimir Ezhov

We determine the maximal hyperbolic reflection groups associated to the quadratic forms $-3x_0^2 + x_1^2 + ... + x_n^2$, $n \ge 2$, and present the Coxeter schemes of their fundamental polyhedra. These groups exist in dimensions up to 13,…

Group Theory · Mathematics 2010-09-29 John Mcleod

We classify the polycyclic totally ordered simple dimension groups, i.e. dimension groups given by a dense embedding of n-dimensional lattice into the real line. Our method is based on the geometry of simple geodesics on the hyperbolic…

Operator Algebras · Mathematics 2016-02-04 Igor Nikolaev

We give new information about the geometry of closed, orientable hyperbolic 3-manifolds with 4-free fundamental group. As an application we show that such a manifold has volume greater than 3.44. This is in turn used to show that if M is a…

Geometric Topology · Mathematics 2020-11-04 Marc Culler , Peter B. Shalen

We define the Kobayashi quotient of a complex variety by identifying points with vanishing Kobayashi pseudodistance between them and show that if a compact complex manifold has an automorphism whose order is infinite, then the fibers of…

Differential Geometry · Mathematics 2017-04-12 Fedor Bogomolov , Ljudmila Kamenova , Steven Lu , Misha Verbitsky

We classify the boundaries of hyperbolic groups that have enough quasiconvex codimension-1 surface subgroups with trivial or cyclic intersections.

Group Theory · Mathematics 2022-02-04 Benjamin Beeker , Nir Lazarovich

We construct new examples of Kobayashi hyperbolic hypersurfaces in the projective 4-space. They are generic projections of the triple symmetric product of a generic curve of genus at least 7, smoothly embedded in the projective 7-space.

Algebraic Geometry · Mathematics 2007-05-23 Ciro Ciliberto , Mikhail Zaidenberg

It is known that the volume function for hyperbolic manifolds of dimension $\geq 3$ is finite-to-one. We show that the number of nonhomeomorphic hyperbolic 4-manifolds with the same volume can be made arbitrarily large. This is done by…

Geometric Topology · Mathematics 2016-09-07 Dubravko Ivanšić

We show that if a compact Kahler manifold X admits a cohomologically hyperbolic surjective endomorphism then its Kodaira dimension is non-positive. This gives an affirmative answer to a conjecture of Guedj in the holomorphic case. The main…

Dynamical Systems · Mathematics 2018-09-24 De-Qi Zhang

A closed connected hyperbolic $n$-manifold bounds geometrically if it is isometric to the geodesic boundary of a compact hyperbolic $(n+1)$-manifold. A. Reid and D. Long have shown by arithmetic methods the existence of infinitely many…

Geometric Topology · Mathematics 2020-06-25 Alexander Kolpakov , Bruno Martelli , Steven T. Tschantz

We make a connection between the structure of the bidisc and a distinguished subgroup of its automorphism group. The automorphism group of the bidisc, as we know, is of dimension six and acts transitively. We observe that it contains a…

Complex Variables · Mathematics 2023-08-16 Anindya Biswas , Anwoy Maitra

We construct spectral sequences for computing the cohomology of automorphism groups of formal groups with complex multiplication by a $p$-adic number ring. We then compute the cohomology of the group of automorphisms of a height four formal…

Algebraic Topology · Mathematics 2021-11-10 A. Salch

It is clear that the full automorphism group of the $(15,8,4)$-design of points and hyperplane complements of ${\rm PG}(3,2)$ is ${\rm GL}(4,2)$. Using methods of point-line geometries, we determine the full automorphism groups of the…

Combinatorics · Mathematics 2025-07-15 Mark Pankov , Krzysztof Petelczyc , Mariusz Żynel

Hyperelliptic manifolds are natural generalizations of hyperelliptic surfaces in dimensions. We provide a full classification of the groups, which arise as the holonomy group of a 4-dimensional hyperelliptic manifold. The classification is…

Algebraic Geometry · Mathematics 2022-11-16 Andreas Demleitner

For a generic hypersurface $\mathbb{X}^{n-1} \subset \mathbb{P}^n(\mathbb{C})$ of degree \[ d \,\geqslant\, n^{2n} \] (1) $\mathbb{P}^n \big\backslash \mathbb{X}^{n-1}$ is Kobayashi-hyperbolically imbedded in $\mathbb{P}^n$; (2)…

Algebraic Geometry · Mathematics 2018-07-31 Joël Merker

We conjecture that for every dimension n not equal 3 there exists a noncompact hyperbolic n-manifold whose volume is smaller than the volume of any compact hyperbolic n-manifold. For dimensions n at most 4 and n=6 this conjecture follows…

Metric Geometry · Mathematics 2015-04-09 Mikhail Belolipetsky , Vincent Emery

We show that special cycles generate a large part of the cohomology of locally symmetric spaces associated to orthogonal groups. We prove in particular that classes of totally geodesic submanifolds generate the cohomology groups of degree…

Number Theory · Mathematics 2015-01-26 Nicolas Bergeron , John Millson , Colette Moeglin