A $q$-Analogue of de Finetti's Theorem

Abstract

A $q$-analogue of de Finetti's theorem is obtained in terms of a boundary problem for the $q$-Pascal graph. For $q$ a power of prime this leads to a characterisation of random spaces over the Galois field ${\Bbb F}_q$ that are invariant under the natural action of the infinite group of invertible matrices with coefficients from ${\Bbb F}_q$.