Engel lattice-ordered groups

An Engel l-group generating a proper normal-valued l-variety is shown to be o-approximable. It is also established that for every proper normal-valued l-varietyF, the class (F) of Engel l-groups from F is a torsion class.Translated fromAlgebra i Logika, Vol. 34, No. 4, pp. 398–404, July-August, 1995.     

Engel groups I

In this series of papers we study Engel groups through their presentation, using Small Cancellation Theory. In the present paper we describe the consequences of a single Engel relator.     

Engel groups II

We study m-dimensional real submanifolds M with (m − 1)-dimensional maximal holomorphic tangent subspace in complex projective space. On these manifolds there exists an almost contact structure F which is naturally induced from the ambient space and in this paper we study the condition h(FX, Y) − h(X, FY) = g(FX, Y)η, η ∈ T ^⊥(M), on the almost contact structure F and on the second fundamental form h of these submanifolds and we characterize certain model spaces in complex projective space.     

Engel groups III

Let F denote a free group. An n-Engel word of F is an iterated commutator of the form [A, nB], where (A,B) is a pair of elements of F, which we here assume to generate a non-cyclic subgroup of F. This is the second of a series of three papers that examine some of the properties of a group defined by a suitable set of relators of the form [A _i , nB _i ], i = 1, 2, ...,m (where n is fixed). In the present paper, the techniques of [1] are generalised in a way that permits the application of the conclusions of [1] concerning the nature of the consequences of a single Engel relator to the case of a finite number of n-Engel relators, subject only to some mild hypotheses on the lengths of the relators and the value of n.     

A construction of Engel structures

Every 4-manifold with trivial tangent bundle admits an Engel structure. To cite this article: T. Vogel, C. R. Acad. Sci. Paris, Ser. I 340 (2005).     

Engel conditions and symmetric tensors

In a recent study of Engel Lie rings, Serena Cicalò and Willem de Graaf have given a practical set of conditions for an additively finitely generated Lie ring L to satisfy an Engel condition. We present a simpler and more direct proof of this fact. Our main result generalizes this in the language of tensor algebra, and describes a relatively small generating set for the module generated by all n-th tensor powers of elements of a finitely generated ?-module M, in terms of a generating set for M.     

On Orderable Poly Engel Groups

It is known that an orderable n-Engel group is nilpotent. We show that an orderable group that is an extension of an n-Engel group by an n-Engel group is nilpotent-by-nilpotent. However, a finitely generated orderable poly n-Engel group need not be solvable in general.     

Semilocal rings with Engel conditions

The relation between the Engel structure of a semilocal ring and that of its multiplicative group is investigated. Suppose that every local ring whose multiplicative group satisfies an m-Engel condition for some positive integer m is an f (m)-Engel ring for some function f . It is proved that under this condition a corresponding statement holds for every semilocal ring which is generated by its multiplicative group. Received: 20 September 2005     

Skew Derivations and Engel Conditions

It is known that for a nonzero derivation d of a prime ring R, if a nonzero ideal I of R satisfies the Engel-type identity [[…[[d(x ^{k ₀} ), x ^{k ₁} ], x ^{k ₂} ],…], x ^{k _n} ], then R is commutative. Here we extend this result to a skew derivation of R for a Lie ideal I, which has an immediate corollary that replaces d by an automorphism of R. A related result in two variables is obtained for d a (θ, ?)-derivation.     

Relative local equivalence of Engel structures

The conditions to determine germs of Engel structures relative to arbitrary subsets are studied. We show that germs of Engel structures at a point relative to an arbitrary subset are determined by the algebraic restrictions of the Engel structures themselves to the subset, and the projected algebraic restrictions of the derived even-contact structures to the subset. When the subset is a smooth submanifold, algebraic restriction is equivalent to geometric restriction. Even when the subset is a smooth submanifold, we need a new stricter notion, projected algebraic restriction.     

Engel Theorem for Novikov Algebras

We prove that, if A is left-nil Novikov algebra, then A ² is nilpotent.     

Cartan Subalgebras with Engel Decomposition

Mathematical Notes -     

Horizontal loops in Engel space

A simple proof is given of the following result first observed by Adachi: embedded circles tangent to the standard Engel structure on are classified, up to isotopy via such embeddings, by their rotation number.