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We investigate the existence of left-invariant closed G$_2$-structures on seven-dimensional non-solvable Lie groups, providing the first examples of this type. When the Lie algebra has trivial Levi decomposition, we show that such a…

Differential Geometry · Mathematics 2025-01-03 Anna Fino , Alberto Raffero

This paper is an adaptation of a chapter from an upcoming monograph on noncommutative geometry and quantum groups. We present examples of non compact quantum groups which are deformations of low dimensional Lie groups. The paper is of…

Operator Algebras · Mathematics 2009-12-14 W. Pusz , P. M. Soltan

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 show the correspondence between left invariant flat projective structures on Lie groups and certain prehomogeneous vector spaces. Moreover by using the classification theory of prehomogeneous vector spaces, we classify complex Lie groups…

Differential Geometry · Mathematics 2014-06-16 Hironao Kato

We classify left invariant metrics with nonnegative curvature on SO(3) and U(2).

Differential Geometry · Mathematics 2007-05-23 Nathan Brown , Rachel Finck , Matthew Spencer , Kristopher Tapp , Zhongtao Wu

In the present paper, we describe two geometric notions, holomorphic Norden structures and K\"{a}hler-Norden structures on Hom-Lie groups, and prove that on Hom-Lie groups in the left invariant setting, these structures are related to each…

Differential Geometry · Mathematics 2020-02-11 E. Peyghan , L. Nourmohammadifar , A. Makhlouf , A. Gezer

We define a complex whose cohomology group of order 1 contains the infinitesimal deformations of a Levi flat structure on a smooth manifold. In the case of real analytic Levi flat structures, this cohomology group is the product of the…

Complex Variables · Mathematics 2014-06-24 Paolo de Bartolomeis , Andrei Iordan

We show that complex symplectic structures need not be preserved under small deformations, and we find sufficient conditions for this to happen. We study various cohomologies of compact complex symplectic manifolds, obtaining some…

Differential Geometry · Mathematics 2025-07-08 Giovanni Bazzoni , Marco Freibert , Adela Latorre , Nicoletta Tardini

This is a short presentation of some classical results on finite dimensional complex Lie algebras (classification of nilpotent Lie algebras, deformations and perturbations, contractions and rigidity). We present some applications to…

Rings and Algebras · Mathematics 2008-05-06 Michel Goze

It was shown by Samelson and Wang that each compact Lie group K of even dimension admits left-invariant complex structures. When K has odd dimension it admits a left-invariant CR-structure of maximal dimension. This has been proved recently…

Differential Geometry · Mathematics 2007-05-23 J. -J. Loeb , M. Manjarin , M. Nicolau

In this paper, we consider left-invariant para-complex structures on six-dimensional nilpotent Lie groups. A complete list of six-dimensional nilpotent Lie groups that admit para-K\"{a}hler structures is obtained, explicit expressions for…

Differential Geometry · Mathematics 2022-08-16 Nikolay K. Smolentsev

This is a survey on left invariant semi-Riemannian metrics on compact Lie groups.

Differential Geometry · Mathematics 2025-05-19 Abdelghani Zeghib

We study the structure of Lie groups admitting left invariant abelian complex structures in terms of commutative associative algebras. If, in addition, the Lie group is equipped with a left invariant Hermitian structure, it turns out that…

Differential Geometry · Mathematics 2011-07-01 Adrian Andrada , Maria Laura Barberis , Isabel Dotti

A bi-invariant differential 2-form on a Lie group G is a highly constrained object, being determined by purely linear data: an Ad-invariant alternating bilinear form on the Lie algebra of G. On a compact connected Lie group these have an…

Differential Geometry · Mathematics 2023-11-08 David Michael Roberts

We give a complete classification of left invariant para-K\"ahler structures on four-dimensional simply connected Lie groups up to an automorphism. As an application we discuss some curvatures properties of the canonical connection…

Symplectic Geometry · Mathematics 2021-04-20 Wadia Mansouri , Ahmad Oufkou

We study generalized complex cohomologies of generalized complex structures constructed from certain symplectic fibre bundles over complex manifolds. We apply our results in the case of left-invariant generalized complex structures on…

Differential Geometry · Mathematics 2017-12-12 Daniele Angella , Simone Calamai , Hisashi Kasuya

Using elementary algebraic arguments, it is shown that $SU(2)^{m}:=SU(2)\times \cdots \times SU(2)$ ($m$ times) admits no left-invariant hypercomplex structures for all $m\ge 1$. This result answers (in a clear and easily accessible way)…

Differential Geometry · Mathematics 2025-09-05 David N. Pham

In this paper, left-invariant almost contact metric structures on three-dimensional non-unimodular Lie groups are investigated. It is proved that for every Riemannian Lie group, there is one of these structures. In addition, left-invariant…

Differential Geometry · Mathematics 2020-02-12 Pejhman Vatandoost-Miandehi , A. Razavi

Gromov asked if the bi-invariant metrics on a compact Lie group are extremal compared to any other metrics. In this note, we prove that the bi-invariant metrics on a compact connected semi-simple Lie group $G$ are extremal (in fact rigid)…

Differential Geometry · Mathematics 2020-07-28 Yukai Sun , Xianzhe Dai

This paper deals essentially with affine or projective transformations of Lie groups endowed with a flat left invariant affine or projective structure. These groups are called flat affine or flat projective Lie groups. Our main results…

Differential Geometry · Mathematics 2016-02-29 Alberto Medina , Omar Saldarriaga , Hernan Giraldo