We briefly review and illustrate our procedure to ‘decouple’ by transformation of generators: either a Hopf algebra H from a Hmodule algebra A1 in their cross-product A1>⊳H; or two (or more) H-module algebras A1,A2. These transformations are based on the existence of an algebra map A1>⊳H → A1. Preprint 02-64 Dip. Matematica e Applicazioni, Università di Napoli DSF/29-2002 ∗Contribution to the P...

We generalize and prove a hypothesis by V. Arnold on the parity of Frobenius number. For the case of symmetric semigroups with three generators of Frobenius numbers we found an exact formula, which in a sense is the sum of two Sylvester’s formulaes. We prove that the fraction of the symmetric semigroups is vanishing in the weak limit. 1. Definitions Take n mutually prime numbers a1, a2, ..., an...

OBJECTIVE Aneurysms originating from the proximal segment (A1) of the anterior cerebral artery are rare; however, because of their small size, the risk of injury of perforating arteries, and the location of the aneurysm in the surgical field, they are challenging to treat. We report on 15 patients with A1 aneurysms and review surgical views according to the direction of aneurysms. METHODS Fif...

Quaternionic representations of Coxeter (reflection) groups of ranks 3 and 4, as well as those of E8, have been used extensively in the literature. The present paper analyses such Coxeter groups in the Clifford Geometric Algebra framework, which affords a simple way of performing reflections and rotations whilst exposing more clearly the underlying geometry. The Clifford approach shows that the...