Noncommutative symmetric functions III : Deformations of Cauchy and convolution algebras

[in "Special Issue : Lie Computations", G. Jacob, V. Koseleff, Eds.]International audienceThis paper discusses various deformations of free associative algebras and of their convolution algebras. Our main examples are deformations of noncommutative symmetric functions related to families of idempotents in descent algebras, and a simple q-analogue of the shuffle product, which has unexpected connections with quantum groups, hyperplane arrangements, and certain questions in mathematical physics (the quon algebra, generalized Brownian motion)