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For every $d\ge 3$, we construct a noncompact smooth $d$-dimensional Riemannian manifold with strictly positive sectional curvature without isoperimetric sets for any volume below $1$. We construct a similar example also for the relative…

Differential Geometry · Mathematics 2024-05-30 Gioacchino Antonelli , Federico Glaudo

Kennard, Khalili Samani, and Searle showed that for a $\mathbb{Z}_2$-torus acting on a closed, positively curved Riemannian $n$-manifold, $M^{n}$, with a non-empty fixed point set for $n$ large enough and $r$ approximately half the…

Differential Geometry · Mathematics 2024-09-25 Farida Ghazawneh

We present examples, both compact and non-compact complete, of lo- cally non-homogeneous proper A-manifolds.

Differential Geometry · Mathematics 2008-02-19 Wlodzimierz Jelonek

The null splitting theorem (proved in math.DG/9909158) is discussed. As an application, a uniqueness theorem for Minkowski space and for de Sitter space associated with the occurrence of null lines (inextendible globally achronal null…

General Relativity and Quantum Cosmology · Physics 2007-05-23 Gregory J. Galloway

We develop the basic properties of $R^{(2)}$-modules, introduce the concept of zero divisor manifolds, construct projective $R^{(2)}$-space which generalizes the real projective space, and initiate the study of the counterpart of symplectic…

Symplectic Geometry · Mathematics 2025-05-14 Keqin Liu

We provide examples of nonseparable spaces $X$ for which C(X) admits an isometric shift of type I, which solves in the negative a problem proposed by Gutek {\em et al.} (J. Funct. Anal. {\bf 101} (1991), 97-119). We also give two…

Functional Analysis · Mathematics 2007-07-18 Jesus Araujo

We present simple examples of finite-dimensional connected homogeneous spaces (they are actually topological manifolds) with nonhomogeneous and nonrigid factors. In particular, we give an elementary solution of an old problem in general…

Geometric Topology · Mathematics 2012-03-21 M. Cárdenas , F. F. Lasheras , A. Quintero , D. Repovš

In each dimension of the form $4n-1$ with $n\geq 3$, we construct infinitely many new examples of manifolds admitting metrics with positive sectional curvature almost everywhere. In addition, we show that if $n\geq 6$, infinitely many of…

Differential Geometry · Mathematics 2025-11-25 Jason DeVito , Joan West

For point $x$ in the inverse limit space $X$ with a single unimodal bonding map we construct, with the use of symbolic dynamics, a planar embedding such that $x$ is accessible. It follows that there are uncountably many non-equivalent…

Dynamical Systems · Mathematics 2016-09-12 Ana Anusic , Henk Bruin , Jernej Cinc

Given a connected, compact, totally geodesic submanifold Y^m of noncompact type inside a compact locally symmetric space of noncompact type X^n, we provide a sufficient condition that ensures that [Y^m] is nonzero in H_m(X^n; R); in low…

Geometric Topology · Mathematics 2009-07-29 Jean-Francois Lafont , Benjamin Schmidt

We present an example of a zero-dimensional $F$-space that is not strongly zero-dimensional.

General Topology · Mathematics 2022-02-16 Alan Dow , Klaas Pieter Hart

For a symplectic manifold with an anti-symplectic involution having non-empty fixed locus, we construct a model of the moduli space of real sphere maps out of moduli spaces of decorated disk maps and give an explicit expression for its…

Symplectic Geometry · Mathematics 2015-10-29 Penka Georgieva

We construct examples of four dimensional manifolds with Spin$^c$-structures, whose moduli spaces of solutions to the Seiberg-Witten equations, represent a non-trivial bordism class of positive dimension, i.e. the Spin$^c$-structures are…

Differential Geometry · Mathematics 2007-05-23 Heberto del Rio Guerra

We construct non-trivial vacuum space-times with a global Scri. The construction proceeds by proving extension results across compact boundaries for initial data sets, adapting the gluing arguments of Corvino and Schoen. Another application…

General Relativity and Quantum Cosmology · Physics 2009-11-07 Piotr T. Chrusciel , Erwann Delay

A Lambda (Card Lambda > aleph)-product space of {0,1} has a partition {X1,...,Xn} for any n a decomposition space of each Xi of which is self-similar.(February 16, 2015)

General Topology · Mathematics 2015-02-19 Akihiko Kitada , Shousuke Ohmori , Tomoyuki Yamamoto

Bredon has constructed a 2-dimensional compact cohomology manifold which is not homologically locally connected, with respect to the singular homology. In the present paper we construct infinitely many such examples (which are in addition…

Algebraic Topology · Mathematics 2008-05-14 Umed H. Karimov , Dušan Repovš

We consider box spaces of finitely generated, residually finite groups $G$, and try to distinguish them up to coarse equivalence. We show that, for $n\geq 2$, the group $SL_n(\mathbb{Z})$ has a continuum of box spaces which are pairwise…

Group Theory · Mathematics 2015-09-07 Ana Khukhro , Alain Valette

Two (strongly) zero-dimensional Lindel\"of topological groups whose product has positive covering dimension are constructed. An example of a Lindel\"of (strongly) zero-dimensional space whose free and free Abelian topological groups are not…

General Topology · Mathematics 2022-07-12 Ol'ga Sipacheva

We construct a space ${X}$ that has a Lusin $\pi$-base and such that ${X}^{2}$ has no Lusin $\pi$-base.

General Topology · Mathematics 2018-12-11 Mikhail Patrakeev

Let X be a finitistic space with non-trivial cohomology groups H^in(X;Z)=Z with generators v_i, where i = 0, 1, 2, 3. We say that X has cohomology type (a, b) if v_1^2 = av_2 and v_1v_2 = bv_3 . In this note, we determine the mod 2…

Algebraic Topology · Mathematics 2008-08-12 Hemant Kumar Singh , Tej Bahadur Singh