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On rainbowness of semiregular polyhedra

Stanislav Jendroľ, Štefan Schrötter (2008)

Czechoslovak Mathematical Journal

We introduce the rainbowness of a polyhedron as the minimum number k such that any colouring of vertices of the polyhedron using at least k colours involves a face all vertices of which have different colours. We determine the rainbowness of Platonic solids, prisms, antiprisms and ten Archimedean solids. For the remaining three Archimedean solids this parameter is estimated.

On Rusakov’s n -ary r s -groups

Wiesław Aleksander Dudek, Zoran Stojaković (2001)

Czechoslovak Mathematical Journal

Properties of n -ary groups connected with the affine geometry are considered. Some conditions for an n -ary r s -group to be derived from a binary group are given. Necessary and sufficient conditions for an n -ary group < θ , b > -derived from an additive group of a field to be an r s -group are obtained. The existence of non-commutative n -ary r s -groups which are not derived from any group of arity m < n for every n 3 , r > 2 is proved.

On sets of vectors of a finite vector space in which every subset of basis size is a basis

Simeon Ball (2012)

Journal of the European Mathematical Society

It is shown that the maximum size of a set S of vectors of a k -dimensional vector space over 𝔽 q , with the property that every subset of size k is a basis, is at most q + 1 , if k p , and at most q + k p , if q k p + 1 4 , where q = p k and p is prime. Moreover, for k p , the sets S of maximum size are classified, generalising Beniamino Segre’s “arc is a conic” theorem. These results have various implications. One such implication is that a k × ( p + 2 ) matrix, with k p and entries from 𝔽 p , has k columns which are linearly dependent. Another is...

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