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We present two constructions of complex symplectic structures on Lie algebras with large abelian ideals. In particular, we completely classify complex symplectic structures on almost abelian Lie algebras. By considering compact quotients of…

Differential Geometry · Mathematics 2023-08-30 Giovanni Bazzoni , Marco Freibert , Adela Latorre , Nicoletta Tardini

Each Abelian subgroup of the fundamental group of a compact and locally simply connected $d$-dimensional length space with no conjugate points is isomorphic to $\mathbb{Z}^k$ for some $0 \leq k \leq d$. It follows from this and previously…

Differential Geometry · Mathematics 2025-04-24 James Dibble

We classify closed abelian subgroups of a compact simple Lie group of adjoint type and of type E having centralizer of the same dimension as the dimension of the subgroup and describe Weyl groups of maximal abelian subgroups.

Group Theory · Mathematics 2014-03-12 Jun Yu

We show that a complex structure on a nilpotent almost abelian real Lie algebra is unique if it exists. As a consequence, we get full control over the cohomology and deformations of almost abelian complex nilmanifolds.

Differential Geometry · Mathematics 2025-02-06 Adrián Andrada , Romina M. Arroyo , María L. Barberis , Sönke Rollenske , Konstantin Wehler

The class of locally compact near abelian groups is introduced and investigated as a class of metabelian groups formalizing and applying the concept of scalar multiplication. The structure of locally compact near abelian groups and its…

Group Theory · Mathematics 2017-02-14 Karl H. Hofmann , Wolfgang Herfort , Francesco G. Russo

Let $G$ be a finite almost simple group with socle $G_0$. In this paper we prove that whenever $G/G_0$ is abelian, then there exists an abelian subgroup $A$ of $G$ such that $G=AG_0$. We propose a few applications of this structural…

Group Theory · Mathematics 2025-01-29 Mauro Costantini , Andrea Lucchini , Daniele Nemmi

We classify closed abelian subgroups of the automorphism group of any compact classical simple Lie algebra whose centralizer has the same dimension as the dimension of the subgroup, and describe Weyl groups of maximal abelian subgroups.

Group Theory · Mathematics 2014-03-12 Jun Yu

It is proved that any infinite Abelian group of infinite exponent admits a non-discrete reflexive group topology.

General Topology · Mathematics 2009-06-04 S. S. Gabriyelyan

We study topological groups having all closed subgroups (totally) minimal and we call such groups c-(totally) minimal. We show that a locally compact c-minimal connected group is compact. Using a well-known theorem of Hall and Kulatilaka…

General Topology · Mathematics 2021-06-29 Wenfei Xi , Menachem Shlossberg

We study groups that can be defined as Polish, pro-countable groups, as non-archimedean groups with an invariant metric or as quasi-countable groups, i.e., closed subdirect products of countable, discrete groups, endowed with the product…

Group Theory · Mathematics 2015-04-16 Maciej Malicki

We describe simply connected compact exceptional simple Lie groups in very elementary way. We first construct all simply connected compact exceptional Lie groups G concretely. Next, we find all involutive automorphisms of G, and determine…

Differential Geometry · Mathematics 2009-02-04 Ichiro Yokota

We prove that every countable subgroup of a compact metrizable abelian group has a characterizing set. As an application, we answer several questions on maximally almost periodic (MAP) groups and give a characterization of the class of…

General Topology · Mathematics 2007-05-23 Dikran Dikranjan , Kenneth Kunen

Let $G$ be a connected Lie group, $C$ be the maximal compact connected subgroup of the center of $G$, and let Aut$(G)$ denote the group of Lie automorphisms of $G$, viewed, canonically, also as a subgroup of GL$(\frak G)$, where $\frak G$…

Group Theory · Mathematics 2025-04-29 S. G. Dani , Riddhi Shah

We study manifolds endowed with an (almost) even Clifford (hermitian) structure and admitting a large automorphism group. We classify them when they are simply connected and the dimension of the automorphism group is maximal, and also prove…

Differential Geometry · Mathematics 2016-06-07 Gerardo Arizmendi , Rafael Herrera , Noemi Santana

A pro-Lie group $G$ is a topological group such that $G$ is isomorphic to the projective limit of all quotient groups $G/N$ (modulo closed normal subgroups $N$) such that $G/N$ is a finite dimensional real Lie group. A topological group is…

Group Theory · Mathematics 2018-12-13 Rafael Dahmen , Karl-Heinrich Hofmann

Generalizing results from \cite{DTk,DU} we study the fine structure of locally minimal (locally) precompact Abelian groups (these are the locally essential subgroups $G$ of LCA groups $L$, i.e., such that $G$ non-trivially meets all…

Group Theory · Mathematics 2025-10-21 Dikran Dikranjan , Wei He , Dekui Peng

We study locally compact group topologies on semisimple Lie groups. We show that the Lie group topology on such a group $S$ is very rigid: every 'abstract' isomorphism between $S$ and a locally compact and $\sigma$-compact group $\Gamma$ is…

Group Theory · Mathematics 2011-08-09 Linus Kramer

We observe that abelian subgroups of Helly groups are finitely generated, and consequently, soluble subgroups of Helly groups are virtually abelian.

Group Theory · Mathematics 2022-10-21 Motiejus Valiunas

Without assuming the field structure on the additive group of real numbers $\mathbb{R}$ with the usual order $<,$ we explore the fact that every proper subgroup of $\mathbb{R}$ is either closed or dense. This property of subgroups of the…

Number Theory · Mathematics 2014-05-21 Jitender Singh

We study locally compact groups having all dense subgroups (locally) minimal. We call such groups densely (locally) minimal. In 1972 Prodanov proved that the infinite compact abelian groups having all subgroups minimal are precisely the…

General Topology · Mathematics 2018-08-24 Wenfei Xi , Dikran Dikranjan , Menachem Shlossberg , Daniele Toller