Journal of Mathematics

Volume 2019, Article ID 2409193, 9 pages

https://doi.org/10.1155/2019/2409193

## Relations of the Algebra of Polynomial Integrodifferential Operators

Universite Marien Ngouabi, Faculté des Sciences et Technique, Parcours Mathematiques, BP: 69, Brazzaville, Congo

Correspondence should be addressed to Andre S. E. Mialebama Bouesso; moc.liamg@seduetnias

Received 7 January 2019; Accepted 19 February 2019; Published 18 March 2019

Academic Editor: Andrei V. Kelarev

Copyright © 2019 Andre S. E. Mialebama Bouesso and G. Mobouale Wamba. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

#### Abstract

We revisit the algebra of polynomial integrodifferential operators and we give a generalization of its relations. Generators of prime ideals of height 1, of the maximal ideal, and of the smallest ideal of are discussed. A technique for obtaining a generating set for a given two-sided ideal of is also discussed.

#### 1. Introduction

The algebra of polynomial integrodifferential operators was introduced in [1] and was studied extensively in [2–6]. Early in 2009, the author of [1] introduced the Jacobian algebra (see [7]) which has similar properties to the algebra of polynomial integrodifferential operators and both algebras are ideally equivalent. In 2010, the same author introduced the algebra (see [8]) of one-sided inverses of a polynomial algebra which is a generalized Weyl algebra as well as the Jacobian algebra and the algebra of polynomial integrodifferential operators . As applications, the algebra of polynomial integrodifferential operators has interesting applications in computer algebra as described in [9, 10]. Our goal in this work is to firstly study new relations of the algebra of polynomial integrodifferential operators in order to facilitate the use of this algebra in a computational point of view. Our starting point is to prove some relations introduced in [1] in Proposition 4. What is more, we give a generalization of these relations in Corollary 7 and then we give new other relations in Lemma 10. In the second part of this paper we study generators of the ideals of . Prime ideals of height 1 listed in [1] are revisited in Theorem 11, sets of generators of the only maximal ideal and of the smallest ideal of are studied, and a given two-sided ideal of is also discussed. The relations discussed in this paper can be used to revisit the special case of , and some results were obtained in the general case of Generalized Weyl algebras especially those described in [11–16].

#### 2. Relations of

Let be a field and be a polynomial ring over . Denote .

*Definition 1. *By a Weyl algebra we mean the free associative algebra satisfying and where .

*Definition 2. *By the algebra of polynomial integro-differential operators we mean the algebra generated by the Weyl algebra and endomorphisms i.e

*Remark 3. *Observe that for Set ; regarding as the identity map of , we have the endomorphismDenoting , we see that ; that is, . From here, we recall Proposition 2.2 introduced in [1].

Proposition 4 (see Proposition 2.2, [1]). *(1) The algebra is generated by the elements that satisfy the following defining relations: ,(a);(b);(c);(d);(e)For , we have .(2)The algebra is a Generalized Weyl algebra where and . Moreover, the algebra is graded where , where and such that(3)Each element of is a unique finite sum for unique elements .*

*Proposition 5 proves the first item of Proposition 4 left in [1].*

*Proposition 5. The algebra satisfies the following relations: (1);(2);(3);(4)(5);(6)For , we have .*

*Proof. *(1).(2)By definition Thus, .(3).(4).(5). Observe that since .(6)Applying Remark 3, where and for all , then we have . Using now Definition 1, we see that

*Setting , we easily see that where .*

*Example 6 (construction of ). *Let us consider the polynomial ring in two indeterminates. By a monomial in we mean an element of the form where , and by a polynomial we mean a finite linear combination of monomials. Consider the following operators: O1O2O3O4O5O6The algebra of polynomial integrodifferential operators is the free associative algebra generated by the operators defined in O1,...,O6 with coefficients in and multiplication given by the composition of applications. The relations between operators are given by Proposition 5.

*With notations as above we have the following result.*

*Corollary 7. For we have (1);(2);(3);(4);(5);(6);(7).*

*Proof. *(1) For we have By Proposition 5 we have . Replacing this in the previous expression we haveObserve that Replacing this in the previous expression we have the following.By induction using the same technique we see that For we haveWe have seen that , and using this we haveBy induction we easily see that(2)Using Proposition 5 we see that . Applying the same techniques as in the previous item we see that (3) By Proposition 5 we see that and then Observe that and replacing this in we see thatBy we see that and combining and we have(4) Using the same technique as in the previous item and the fact that we see that (5)since we have shown above that . Observe that Replacing all this in we have the following result:Now let us prove that . Observe that Observe that , and using this in we have the following result: Now it becomes easy to see that (6) The same techniques as in the previous item can be easily applied.

*Example 8 (application). *Let be a univariate polynomial ring and let us consider the algebra constructed from ; we have . Setting , one can study the noncommutative polynomial ring . (1)* Monomials in *: in our case monomials are of the form where . Note that are not monomials but polynomials for since by Corollary 7 we have(i);(ii).(2)* Polynomials in *: a polynomial in is a linear combination of monomials. As a specific case, let us consider the polynomial . According to the order we have imposed to our variables, this polynomial is not well-organized. Observe that after considering (1) in Proposition 5 and (1) in Corollary 7. Replacing in we get Using (5) in Corollary 7 we get

*We have seen in [1] that where and the only proper ideal of is .*

*Corollary 9. (1) The algebra is principal and its only proper ideal is ;(2) is an module.*

*Proof. *Consider the notation above.

(1) We have seen in [1] that the only proper ideal of is . Let us now prove that .

Let ; then Observe that each term of belongs in as a two-sided ideal; therefore .

The converse is straightforward since .

(2) can be regarded as an module. Moreover, We easily see that the external multiplication is only concern with .

*Lemma 10. For and , (1);(2);(3);(4);(5).*

*Proof. *(1)Seeing that algebra is associative and the fact that (by Proposition 4), then Furthermore .(2). Observe that But (3).(4).(5).(a)If then and , since then .(b)If , then and , since .

*3. Two-Sided Ideals of *

*3. Two-Sided Ideals of**The theory of ideals of is already studied in [1]. The goal of this section is to study generating sets of those ideals and to study the behavior of a given ideal.*

*3.1. Generators of Primes Ideals of Height 1*

*3.1. Generators of Primes Ideals of Height 1**Corollary 3.3 in [1] proved that the only prime ideals of of height 1 are *

*where .*

*With notations as above we have the following result.*

*Theorem 11. For we have for some .*

*Proof. *By definition where If , then where and .

Observe that ; that is, where for . By Proposition 2.2 in [1], we see that where and .

It is easy to see as a two-sided ideal of . Observe that We then have

since ; i.e., if we haveThis means that for ; thus implies straightforwardly Using the same technique as above, we have Thus

*Corollary 12. (1)The only maximal ideal of is where .(2)The smallest nonzero ideal of is .*

*Proof. *It is well known (see [1]) that (1)the only maximal ideal of is that is, (2)the smallest nonzero ideal of is It is straightforward to see that . We prove the converse for since the general case can be obtained by induction. Let ; then . That is, for some . That is,for , and .

We have the following.Let us expand (58):since different variable commutes. Observe that

for ; this leads to . To avoid this, let us take ; in this case we have the following.Observe that

for some . This is because(i) and;(ii) since .Observe also that

for some (using Corollary 7).

Replacing this in we getSince different variable commutes, we have by Proposition 5(6), and this leads directly to . To avoid this case, we take ; in this case becomesAgain since different variable commutes, we have Replacing this in we getObserve the following.In any of these cases we finish with an expression of the form for some and ; thusLet us expand (59). Applying the same technique as in (58) we getwhere and .

In (68) we see that and in (69) ; thus

*Example 13. *Let us consider again the algebra . The maximal ideal of is where and for some polynomials and . Thus . The smallest ideal is .

*3.2. Generators of Ideals of *

*3.2. Generators of Ideals of**Let be a two-sided ideal of ; then can be written as .*

*For , let ; then *

*It is proven in [1], Proposition 2.2, that where and For we have where and . Thus we have the following.*

*(1) If each , then *

*Observe that *

*and ; this implies the following.*

*If *

*note that *

*and then*

*(2) Assume without loss of generalities that there exist such that *

*and in this case*