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Abstract: This paper explores the certification of properties of an efficient functional program in the area of symbolic computation: the calculation of Gröbner basis of a set of multivariate polynomials. Our experience in the development of industrial systems and the certification of some of its relevant properties has led us to use a methodology consisting of functional programs to write the code and the formal verification of fundamental properties. The functional language objective caml has been chosen to implement the program. To verify the properties two approaches are explored: manual proofs that reason directly over the source code of the algorithms, applying techniques like equational reasoning, and theorem provers that are used as a tool to help us certify a model of the real system. The chosen proof assistant is coq. Not only will the certification of the software be taken into consideration but also its efficiency. In addition, we present a graphical interface which eases the use of the program. [Copyright &y& Elsevier]

Abstract: An algorithm is presented that computes explicit generators for the ring of differential operators on an orbifold, the quotient of a complex vector space by a finite group action. The algorithm also describes the relations among these generators. The algorithm presented in this paper is based on Schwarz’s study of a map carrying invariant operators to operators on the orbifold and on an algorithm to compute rings of invariants using Gröbner bases due to Derksen [Derksen, Harm, 1999. Computation of invariants for reductive groups. Adv. Math. 141 (2), 366–384]. It is also possible to avoid using Derksen’s algorithm, instead relying on the Reynolds operator and the Molien series. [Copyright &y& Elsevier]

Let An(k) be the Weyl algebra, with k a field of characteristic zero. It is known that every projective finitely generated left module is free or isomorphic to a left ideal. Let M be a left submodule of a free module. In this paper we give an algorithm to compute the projective dimension of M. If M is projective and rank(M)≥2 we give a procedure to find a basis. [Copyright &y& Elsevier]