Steinitz classes of unimodular lattices

Steinitz classes of unimodular lattices

For each prime l with l ≡ 7 (mod 8), we define an action of the ring O = Z[ 2(1 + √ −l)] on the unimodular lattice D l+1 using a Paley matrix. We determine the isomorphism class of D l+1 as an O-module. In particular we show that unless l = 7, D l+1 is not a free O-module. We note a consequence for the Leech lattice.

Conference Matrices and Unimodular Lattices

We use conference matrices to define an action of the complex numbers on the real Euclidean vector space R. In certain cases, the lattice D n becomes a module over a ring of quadratic integers. We can then obtain new unimodular lattices, essentially by multiplying the lattice D n by a non-principal ideal in this ring. We show that lattices constructed via quadratic residue codes, including the ...

Universal codes and unimodular lattices

Binary quadratic residue codes of length p + 1 produce via construction B and density doubling type II lattices like the Leech. Recently, quaternary quadratic residue codes have been shown to produce the same lattices by construction A modulo 4. We prove in a direct way the equivalence of these two constructions for p ~ 31. In dimension 32, we obtain an extremal lattice of type II not isometric...

On automorphisms of extremal even unimodular lattices

The automorphism groups of the three known extremal even unimodular lattices of dimension 48 and the one of dimension 72 are determined using the classification of finite simple groups. Restrictions on the possible automorphisms of 48-dimensional extremal lattices are obtained. We classify all extremal lattices of dimension 48 having an automorphism of order m with φ(m) > 24. In particular the ...

Construction of new extremal unimodular lattices