KT-nearfields of rank 2.
Let denote the symmetric group with letters, and the maximal order of an element of . If the standard factorization of into primes is , we define to be ; one century ago, E. Landau proved that and that, when goes to infinity, .There exists a basic algorithm to compute for ; its running time is and the needed memory is ; it allows computing up to, say, one million. We describe an algorithm to calculate for up to . The main idea is to use the so-called -superchampion...
We consider the following notion of largeness for subgroups of . A group G is large if it contains a free subgroup on generators. We give a necessary condition for a countable structure A to have a large group Aut(A) of automorphisms. It turns out that any countable free subgroup of can be extended to a large free subgroup of , and, under Martin’s Axiom, any free subgroup of of cardinality less than can also be extended to a large free subgroup of . Finally, if Gₙ are countable groups, then...
Deux codages sont utilisés sur l’ensemble des permutations ou ordres totaux sur un ensemble fini à éléments et à chacun de ces codages est associé un produit direct d’ordres totaux. On démontre que le diagramme du treillis permutoèdre (ou ordre de Bruhat faible sur le groupe symétrique ) est intersection des diagrammes des deux produits directs de ordres totaux à éléments.
Malnormal subgroups occur in various contexts. We review a large number of examples, and compare the general situation to that of finite Frobenius groups of permutations.In a companion paper [18], we analyse when peripheral subgroups of knot groups and -manifold groups are malnormal.
A fundamental result in universal algebra is the theorem of Rosenberg describing the maximal subclones in the clone of all operations over a finite set. In group theory, the maximal subgroups of the symmetric groups are classified by the O'Nan-Scott Theorem. We shall explore the similarities and differences between these two analogous major results. In addition, we show that a primitive permutation group of diagonal type can be maximal in the symmetric group only if its socle is the direct product...
Via representation of vertex-transitive graphs on groupoids, we show that left loops with units are factors of groups, i.e., left loops are transversals of left cosets on which it is possible to define a binary operation which allows left cancellation.