arXiv subjects
Publications and source records attributed to Jacques Martinet.
We construct Euclidean lattices whose sets of minimal vectors support some large equiangular families of lines, using notably reduction modulo~$2$ of lattices. %as considered in \cite{Ma1} and \cite{Ma2}. We also consider some related problems, and answer a question raised by Greaves ([G], Subsection~1.3.2).
We enumerate the low dimensional cells in the Voronoi cell complexes attached to the modular groups $SL_N(Z)$ and $GL_N(Z)$ for $N=8,9,10,11$, using quotient sublattices techniques for $N=8,9$ and linear programming methods for higher dimensions. These enumerations allow us to compute some cohomology of these groups and prove that $K_8(Z) = 0$. We deduce from it new knowledge on the Kummer-Vandiver conjecture.
We compare for an $n$-dimensional Euclidean lattice $\Lb$ the smallest possible values of the product of the norms of $n$~vectors which either constitute a basis for $\Lb$ (Hermite-type inequalities) or are merely assumed to be independent (Minkowski-type inequalities). We improve on 1953 results of van der Waerden in dimensions $6$ to $8$ and prove partial result in dimension~$9$.
Let $\Lb$ be a lattice in an $n$-dimensional Euclidean space $E$ and let $\Lb'$ be a Minkowskian sublattice of $\Lb$, that is, a sublattice having a basis made of representatives for the Minkowski successive minima of $\Lb$. We consider the set of possible quotients $\Lb/\Lb'$ which may exists in a given dimension or among not too large values of the index $[\Lb:\Lb']$, indeed $[\Lb:\Lb']\le 4$, or dimension $n\le 8$.
We prove that all Euclidean lattices of dimension $n\le 9$ which are generated by their minimal vectors, also possess a basis of minimal vectors. By providing a new counterexample, we show that this is not the case for all dimensions $n\ge 10$.
Let $Λ$ be a lattice in an $n$-dimensional Euclidean space $E$ and let $Λ'$ be a Minkowskian sublattice of $Λ$, that is, a sublattice having a basis made of representatives for the Minkowski successive minima of $Λ$. We extend the classification of possible $\Z/d\Z$-codes of the quotients $Λ/Λ'$ to dimension~$9$, where $d\Z$ is the annihilator of $Λ/Λ'$.