Codes, lattices, and Steiner systems.
Les réseaux et sont équivalents
On montre que le réseau de Barnes-Wall de rang est équivalent au réseau à double congruence de Martinet. La preuve utilise la notion de voisinage de Kneser et des résultats de Koch et Venkov sur le défaut du voisinage (“Nachbardefekt”).
Universal codes and unimodular lattices
Binary quadratic residue codes of length produce via construction and density doubling type II lattices like the Leech. Recently, quaternary quadratic residue codes have been shown to produce the same lattices by construction modulo . We prove in a direct way the equivalence of these two constructions for . In dimension 32, we obtain an extremal lattice of type II not isometric to the Barnes-Wall lattice . The equivalence between construction modulo plus density doubling and construction...
-modular lattices from ternary codes
The alphabet where is viewed here as a quotient of the ring of integers of by the ideal (3). Self-dual codes for the hermitian scalar product give -modular lattices by construction . There is a Gray map which maps self-dual codes for the Euclidean scalar product into Type III codes with a fixed point free involution in their automorphism group. Gleason type theorems for the symmetrized weight enumerators of Euclidean self-dual codes and the length weight enumerator of hermitian self-dual...
On Robin’s criterion for the Riemann hypothesis
Robin’s criterion states that the Riemann Hypothesis (RH) is true if and only if Robin’s inequality is satisfied for , where denotes the Euler(-Mascheroni) constant. We show by elementary methods that if does not satisfy Robin’s criterion it must be even and is neither squarefree nor squarefull. Using a bound of Rosser and Schoenfeld we show, moreover, that must be divisible by a fifth power . As consequence we obtain that RH holds true iff every natural number divisible by a fifth power...
Symmetric flows and broadcasting in hypercubes
In this paper, we propose a method which enables to construct almost optimal broadcast schemes on an -dimensional hypercube in the circuit switched, -port model. In this model, an initiator must inform all the nodes of the network in a sequence of rounds. During a round, vertices communicate along arc-disjoint dipaths. Our construction is based on particular sequences of nested binary codes having the property that each code can inform the next one in a single round. This last property is insured...
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