Automorphisms and Isometries of Some Modular Algebras

Two explicitations for the primary decomposition of the algebra A=GFq[X1,...,Xn]/(t1(X1),...,tn(Xn)) are used to determine the group of automorphisms of A. In the particular case where A is an algebra of a finite abelian group, we give also its group of isometries.