  In quantum physics, the state space of a countable chain of (n+1)-level atoms
becomes, in the continuous field limit, a Fock space with multiplicity n. In a
more functional analytic language, the continuous tensor product space over R
of copies of the space C^{n+1} is the symmetric Fock space Gamma_s(L^2(R;C^n)).
In this article we focus on the probabilistic interpretations of these facts.
We show that they correspond to the approximation of the n-dimensional normal
martingales by means of obtuse random walks, that is, extremal random walks in
R^n whose jumps take exactly n+1 different values. We show that these
probabilistic approximations are carried by the convergence of the basic matrix
basis a^i_j(p) of $\otimes_N \CC^{n+1}$ to the usual creation, annihilation and
gauge processes on the Fock space.
