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Standard monomials for q-uniform families and a conjecture of Babai and Frankl

Gábor Hegedűs, Lajos Rónyai (2003)

Open Mathematics

Let n, k, α be integers, n, α>0, p be a prime and q=p α. Consider the complete q-uniform family k , q = K n : K k ( m o d q ) We study certain inclusion matrices attached to F(k,q) over the field 𝔽 p . We show that if l≤q−1 and 2l≤n then r a n k 𝔽 p I ( ( k , q ) , n ) n This extends a theorem of Frankl [7] obtained for the case α=1. In the proof we use arguments involving Gröbner bases, standard monomials and reduction. As an application, we solve a problem of Babai and Frankl related to the size of some L-intersecting families modulo q.

Sublattices of certain Coxeter lattices

Anne-Marie Bergé, Jacques Martinet (2005)

Journal de Théorie des Nombres de Bordeaux

In this paper, we describe the sublattices of some lattices, extending previous results of [Ber]. Our description makes intensive use of graphs.

Substitutions, abstract number systems and the space filling property

Clemens Fuchs, Robert Tijdeman (2006)

Annales de l’institut Fourier

In this paper we study multi-dimensional words generated by fixed points of substitutions by projecting the integer points on the corresponding broken halfline. We show for a large class of substitutions that the resulting word is the restriction of a linear function modulo 1 and that it can be decided whether the resulting word is space filling or not. The proof uses lattices and the abstract number system associated with the substitution.

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