Abstract
The main goal of this article is to explore the concepts of graded -2-absorbing and graded -2-absorbing primary submodules as a new generalization of the concepts of graded 2-absorbing and graded 2-absorbing primary submodules. Let be a function, where denotes the collection of graded R-submodules of M. A proper is said to be a graded -2-absorbing R-submodule of M if whenever are homogeneous elements of R and s is a homogeneous element of M with , then or or , and we call K a graded -2-absorbing primary R-submodule of M if whenever are homogeneous elements of R and s is a homogeneous element of M with , then or is in the graded radical of K or . Several properties of these new forms of graded submodules are investigated.
1. Introduction
Throughout this article, G will be a group with identity e and R a commutative ring with nonzero unity 1. Then R is said to be G-graded if with for all where is an additive subgroup of R for all . The elements of are called homogeneous of degree g. If , then x can be written uniquely as , where is the component of x in . It is known that is a subring of R and . The set of all homogeneous elements of R is . Assume that M is a left unitary R-module. Then M is said to be G-graded if with for all where is an additive subgroup of M for all . The elements of are called homogeneous of degree g. It is clear that is an -submodule of M for all . If , then x can be written uniquely as , where is the component of x in . The set of all homogeneous elements of M is . Let K be an R-submodule of a graded R-module M. Then K is said to be graded R-submodule if , i.e., for , where for all . An R-submodule of a graded R-module need not be graded. For more details and terminology, see [1,2].
Specifically, turns out to be a graded ideal of R. May I be an ideal of R, rightly graded. Then the graded radical of I will be , and is defined to be the collection of all so that for every , there exists for which . One can see that if , then if and only if for some . In fact, is a graded ideal of R, see [3]. Let K be a graded R-submodule of M. The graded radical of K is then denoted by and is specified as the intersection of all graded prime submodules of M enclosing K. If no graded prime submodule contains K exists, we can take .
A graded prime (resp. graded primary) R-submodule is a graded R-submodule with the property that for and such that implies that or (resp. or . As graded prime ideals (submodules) have an important role in graded ring (module) theory, several authors generalized these concepts in different ways, see ([4,5,6,7,8]). Atani in [9] has introduced graded weakly prime submodules. A graded R-submodule is called graded weakly prime if whenever and with , then or . The concept of graded -prime submodules has been introduced in [10]. Let be a function, where denotes the collection of graded submodules of M. A graded R-submodule is called graded -prime if whenever and such that , then or .
Graded 2-absorbing ideals (resp. graded weakly 2-absorbing ideals) are introduced in [11] as a different generalization of graded prime ideals (resp. graded weakly prime ideals). A proper graded ideal I of R is a graded 2-absorbing ideal (resp. graded weakly 2-absorbing ideal) of R if whenever and (resp. ), then or or . Then introducing graded 2-absorbing submodules (resp. graded weakly 2-absorbing submodules) in [5] generalized the concept of graded 2-absorbing ideals (resp. graded weakly 2-absorbing ideals) to graded submodules.
Al-Zoubi and Sharafat in [12] proposed the notion of graded 2-absorbing primary ideals, where a proper graded ideal I of R is called graded 2-absorbing primary if whenever with , then or or . The notion of graded 2-absorbing primary submodules is studied in [7] as a generalization of graded 2-absorbing primary ideals. A proper graded R-submodule K of M is said to be a graded 2-absorbing primary R-submodule (resp. graded weakly 2-absorbing primary R-submodule) of M if whenever and with (resp. ), then or or .
A graded R-module M is called a graded multiplication if for any graded R-submodule K, there exists a graded ideal I of R with . In this instance, . Graded multiplication modules were firstly introduced by Escoriza and Torrecillas in [13], and further results were obtained by several authors, see for example [14]. Let N and K be graded R-submodules of a graded multiplication R-module M with and for some graded ideals I and J of R. The product of N and K is denoted by is defined by . Then the product of N and K is independent of presentations of N and K. In fact, as is a graded ideal of R (see [2]), is a graded R-submodule of M and . Moreover, for , by , we mean the product of and . Also, it can be seen in ([8], Theorem 9) that if N is a proper graded R-submodule of a graded multiplication R-module M, then .
In this article, our aim is to extend the notion of graded 2-absorbing submodules to graded -2-absorbing submodules using similar techniques to that are used in [10], and also to extend graded 2-absorbing primary submodules to graded -2-absorbing primary submodules. Our study is inspired by [15].
2. Graded -2-Absorbing and Graded -2-Absorbing Primary Submodules
This segment includes proposing and examining the notions of graded -2-absorbing and graded -2-absorbing primary submodules.
Definition 1.
Let M be a G-graded R-module and be a function.
- 1.
- A graded R-submodule is called graded ϕ-primary submodule if whenever and with , then or .
- 2.
- A graded R-submodule K with for some is called g-ϕ-primary submodule if whenever and with , then or .
- 3.
- A graded R-submodule is called graded ϕ-2-absorbing submodule (ϕ-2-abs. submodule) if whenever and with , then or or .
- 4.
- A graded R-submodule K with for some is called g-ϕ-2-absorbing submodule (g-ϕ-2-abs. submodule) if whenever and with , then or or .
- 5.
- A graded R-submodule of M is called graded ϕ-2-absorbing primary submodule (ϕ-2-abs. prim. submodule) if whenever and with , then or or .
- 6.
- A graded R-submodule K with for some is called g-ϕ-2-absorbing primary submodule (g-ϕ-2-abs. prim. submodule) if whenever and with , then or or .
- 7.
- A proper graded R-submodule K of M is said to be a graded ϕ-almost primary R-submodule of M if whenever and such that , then either or .
Remark 1.
- 1.
- For a graded ϕ-primary R-submodule K of a graded multiplication R-module M, we have the following functions:graded primary submodule,graded weakly primary submodule,graded almost primary submodule,graded n-almost primary submodule, andgraded ω-primary submodule.
- 2.
- Let K be a graded ϕ-2-abs. R-submodule (resp. graded ϕ-2-abs. prim. R-submodule) of a graded multiplication R-module M. Thengraded 2-abs. submodule (resp. graded 2-abs. prim. submodule),graded weakly 2-abs. submodule (resp. graded weakly 2-abs. prim. submodule),graded almost 2-abs. submodule (resp. graded almost 2-abs. prim. submodule),graded n-almost 2-abs. submodule (resp. graded n-almost 2-abs. prim. submodule), andgraded ω-2-abs. submodule (resp. graded ω-2-abs. prim. submodule).
- 3.
- For functions , we write if for all . Obviously, therefore, we have the next order:.
- 4.
- If , then every graded ϕ-2-abs. submodule (resp. graded ϕ-2-abs. prim. submodule) is graded ψ-2-abs. submodule (resp. graded ψ-2-abs. prim.submodule).
Remark 2.
Since for any graded R-submodule K, we may assume without loss of generality, and we will do so throughout this article.
Theorem 1.
Let M be a graded R-module and K be a proper graded R-submodule of M. Then the following implications hold:
- 1.
- K is graded ϕ-prime submodule ⇒K is graded ϕ-2-abs. submodule ⇒K is graded ϕ-2-abs. prim. submodule.
- 2.
- If M is a graded multiplication R-module and K is a graded ϕ-primary submodule, then K is graded ϕ-2-abs. prim. submodule
- 3.
- For graded multiplication R-module M, K is graded 2-abs. submodule ⇒K is graded weakly 2-abs. submodule ⇒K is graded ω-2-abs. submodule ⇒K is graded -almost 2-abs. submodule ⇒K is graded n-almost 2-abs. submodule for all ⇒K is graded almost 2-abs. submodule.
- 4.
- For graded multiplication R-module M, K is graded 2-abs. prim. submodule ⇒K is graded weakly 2-abs. prim. submodule ⇒K is graded ω-2-abs. prim. submodule ⇒K is graded -almost 2-abs. prim. submodule ⇒K is graded n-almost 2-abs. prim. submodule for all ⇒K is graded almost 2-abs. prim. submodule.
- 5.
- Suppose that . Then K is graded ϕ-2-abs. prim. submodule if and only if K is graded ϕ-2-abs. submodule.
- 6.
- If M is a graded multiplication R-module and K is an idempotent graded R-submodule of M, then K is graded ω-2-abs. submodule, and K is graded n-almost 2-abs. submodule for every .
- 7.
- Let M be a graded multiplication R-module. Then K is graded n-almost 2-abs. submodule (resp. graded n-almost 2-abs. prim. submodule) for all if and only if K is graded ω-2-abs. submodule (resp. graded ω-2-abs. prim. submodule).
Proof.
- This is straightforward.
- Let and with . suppose that . Then and then as K is a graded -primary R-submodule. Therefore, . Consequently, K is graded -2-absorbing primary.
- This is clear by Remark 1 (4).
- This is clear by Remark 1 (4).
- The claim is obvious.
- Since K is an idempotent R-submodule, for all , and then . Thus K is a graded -2-abs.. By (3), we conclude that K is a graded n-almost 2-abs. for all .
- Suppose that K is a graded n-almost 2-absorbing (resp. graded n-almost 2-absorbing primary) R-submodule of M for all . Let and with but . Hence for some . Since K is graded n-almost 2-abs. (resp. graded n-almost 2-abs. prim.) for all , this implies either or or (resp. or or ). This completes the first implication. The converse is clear from (3) (resp. from (4)).
□
Proposition 1.
Let M be a graded R-module and K be a graded ϕ-2-abs. prim. submodule of M. If is a graded 2-abs. prim. submodule of M, then K is a graded-2-abs. prim. submodule of M.
Proof.
Let and such that . If , then we conclude that or or since is graded 2-abs. prim., and so the result holds. If , then the result holds easily since K is graded -2-abs. prim. submodule. □
Theorem 2.
Let M be a graded R-module and K be a graded R-submodule of M with . If is a graded ϕ-prime submodule of M, then K is a graded ϕ-2-abs. prim. submodule of M.
Proof.
Let and with and . Because is a graded -prime and , . So, . Consequently, K is a graded -2-abs. prim. of M. □
Next we consider the behaviour of graded -2-absorbing (primary) submodules under graded quotient modules. Let M be a G-graded R-module and K be a graded R-submodule of M. Then is G-graded by for all ([2]).
Lemma 1
([16], Lemma 3.2). Let M be a graded R-module, K be a graded R-submodule of M, and N be an R-submodule of M such that . Then N is a graded R-submodule of M if and only if is a graded R-submodule of .
Theorem 3.
Let M be a graded R-module and K be a proper graded R-submodule of M.
- 1.
- K is a graded ϕ-2-abs. submodule of M if and only if is a graded weakly 2-abs. submodule of .
- 2.
- K is a graded ϕ-2-abs. prim. submodule of M if and only if is a graded weakly 2-abs. prim. submodule of .
- 3.
- K is a graded ϕ-prime submodule of M if and only if is a graded weakly prime submodule of .
- 4.
- K is a graded ϕ-primary submodule of M if and only if is a graded weakly primary submodule of .
Proof.
- Let and with . Then such that , but . Hence or or . So, or or , as desired. Conversely, let and such that and . Then with . Hence or or . So, or or . Thus K is a graded -2-abs.submodule.
- Let and with . Then with , but . Hence either or or . So, or or . The result holds since . One can easily prove the converse.
One can easily prove (3) and (4) along the same lines. □
Next we consider the behaviour of graded -2-absorbing (primary) submodules under graded homomorphisms. Let M and L be two G-graded R-modules. An R-homomorphism is said to be a graded R-homomorphism if for all ([2]).
Lemma 2.
([4], Lemma 2.16). Suppose that is a graded R-homomorphism. If N is a graded R-submodule of L, then is a graded R-submodule of M.
Lemma 3
([17], Lemma 4.8). Suppose that is a graded R-homomorphism. If K is a graded R-submodule of M, then is a graded R-submodule of .
Theorem 4.
Suppose that is a graded R-epimorphism. Let and be functions.
- 1.
- If N is a graded ψ-2-abs. prim. submodule of L and , then is a graded ϕ-2-abs. prim. of M.
- 2.
- If K is a graded ϕ-2-abs. prim. submodule of M containing and , then is a graded ψ-2-abs. prim. submodule of L.
- 3.
- If N is a graded ψ-2-abs. submodule of L and , then is a graded ϕ-2-abs. submodule of M.
- 4.
- If K is a graded ϕ-2-abs. submodule of M containing and , then is a graded ψ-2-abs. submodule of L.
Proof.
- Since f is epimorphism, is proper. Let and with and . Since , . Also, implies that . Thus . Then or or . Thus or or . Since ([18], Theorem 2.16), we should conclude that is a graded -2-abs. prim. submodule.
- Let and with . Because f is a graded epimorphism, there is with . Hence, and so as . Because , we have . Hence . It implies that or or . Thus or or . As implies , we are done.
One can easily prove (3) and (4) along the same lines. □
Next we consider the behaviour of graded -2-absorbing (primary) submodules under multiplicative homogeneous set. Let M be a G-graded R-module and be a multiplicative set. Then is a G-graded -module with for all , and for all . If K is a graded R-submodule of M, then is a graded -submodule of . Let be a function and define by for and otherwise, for every graded R-submodule K of M ([10]).
Theorem 5.
Let M be a graded R-module and be a multiplicative set.
- 1.
- If K is a graded ϕ-2-abs. prim. of M and , then is a graded -2-abs. prim. of .
- 2.
- If K is a graded ϕ-2-abs. of M and , then is a graded -2-abs. of .
Proof.
1. Let and with . Then and with for some , and then or or . So, or or .
Similarly, one can easily prove (2). □
Next we consider the behaviour of graded -2-absorbing (primary) submodules under graded Cartesian product. Let be a G-graded -module, be a G-graded -module and . Then is a G-graded R-module with for all , where for all ([2]).
Lemma 4
([16], Lemma 3.12). Let be a G-graded -module, be a G-graded -module, and . Then is a graded R-submodule of M if and only if N is a graded -submodule of and K is a graded -submodule of .
Lemma 5.
Let be a G-graded -module, be a G-graded -module, and . Suppose that , be functions and . Assume that for some proper graded -submodule of . If K is a graded ϕ-2-abs. submodule of M, then is a graded -2-abs. submodule of .
Proof.
Let and with . Then for with the same degree as , respectively, and for with the same degree as , and with . Since K is a graded -2-abs. submodule of M, we get either or or . So clearly, we conclude that or or . Therefore, is a graded -2-abs. submodule of . □
Theorem 6.
Let be a G-graded -module, be a G-graded -module, and . Suppose that , be functions and . Assume that for some proper graded -submodule of .
- 1.
- If , then K is a graded ϕ-2-abs. submodule of M if and only if is a graded -2-abs. submodule of .
- 2.
- If , then K is a graded ϕ-2-abs. submodule of M if and only if is a graded 2-abs. submodule of .
Proof.
- Suppose that is a graded -2-abs. submodule of . Let and with . Since , we get that and with , and this implies that or or . Thus either or or . Hence, K is a graded -2-abs. submodule of M. The converse holds from Lemma 5.
- Suppose that K is a graded -2-abs. submodule of M. Since , there is and then there is with . Suppose that is not a graded 2-abs. of . By Lemma 5, is a graded -2-abs. of . Hence, there are and with , , and . So, which implies that or or , that is a contradiction. So, is a graded 2-abs. submodule of . Conversely, if is a graded 2-abs. submodule of , then is a graded 2-abs. submodule of M by ([6], Theorem 3.3). Hence K is a graded -2-abs. submodule of M for any .
□
Lemma 6.
Let be a G-graded -module, be a G-graded -module, and . Suppose that , be functions and . Assume that for some proper graded -submodule of . If K is a graded ϕ-2-abs. prim. submodule of M, then is a graded -2-abs. prim. submodule of .
Proof.
The proof uses the same procedure in Lemma 5. □
Theorem 7.
Let be a G-graded -module, be a G-graded -module, and . Suppose that , be functions and . Assume that for some proper graded -submodule of .
- 1.
- If , then K is a graded ϕ-2-abs. prim. submodule of M if and only if is a graded -2-abs. prim. submodule of .
- 2.
- If , then K is a graded ϕ-2-abs. prim. submodule of M if and only if is a graded 2-abs. prim. submodule of .
Proof.
- It can be easily proved by using a similar procedure in Theorem 6 (1).
- Suppose that is a graded 2-abs. prim. submodule of . Then is a graded 2-abs. prim. submodule of M by ([7], Theorem 18). Hence K is a graded -2-abs. submodule of M for any . The remainder of the proof is similar to that of Theorem 6 (2).
□
3. More Results
In this section, we introduce more results concerning the g-components of M, .
Theorem 8.
Let M be a G-graded R-module and K be a g-ϕ-primary submodule of M. Suppose that and such that , and . Then
- 1.
- .
- 2.
- .
- 3.
- .
Proof.
- Suppose that . Then there is with , and then . Since and , we deduce that as K is a g--primary R-submodule of M. So , which is a contradiction. So, .
- Suppose that . Then there is with , and then as . Since , we get . Since , so . Hence , which is a contradiction.
- Suppose that . Then there exist and such that . By (1) and (2), . So, either or . Thus we have either or , which is a contradiction.
□
Remark 3.
Note that if K is a g-ϕ-primary submodule of M which is not g-primary, then there are and with , and . So, every g-ϕ-primary submodule, which is not g-primary, satisfies the assumptions of Theorem 8.
Theorem 9.
Let M be a G-graded R-module, and K be a g-ϕ-2-abs. submodule of M. Suppose that and with , , and . Then
- 1.
- .
- 2.
- .
- 3.
- .
- 4.
- .
Proof.
- Suppose that . Then there is with , and then . Since and , we conclude that or . So, or , which is a contradiction. Thus .
- Suppose that . Then there is with , and then as . Since , we obtain that . Then or or . Hence or or , which is a contradiction. Hence, .
- It can be easily proved by using a similar procedure in part (2).
- Assume that . Then there exist with , and then by parts (2) and (3), . Clearly, . Then or or . Therefore, or or , which is a contradiction. Consequently, .
□
Remark 4.
Note that if K is a g-ϕ-2-abs. submodule of M which is not g-2-abs., then there are and with , , and . So, every g-ϕ-2-abs. submodule, which is not g-2-abs., satisfies the assumptions of Theorem 9.
Theorem 10.
Let M be a G-graded R-module, and K be a g-ϕ-2-abs. prim. submodule of M. Consider and with , , and . Then
- 1.
- .
- 2.
- .
- 3.
- .
- 4.
- .
Proof.
This can be easily proved in a similar way as Theorem 9. □
Remark 5.
Note that if K is a g-ϕ-2-abs. prim. submodule of M which is not g-2-abs. prim., then there are and with , , and . So, every g-ϕ-2-abs. prim. submodule, which is not g-2-abs. prim., satisfies the assumptions of Theorem 10.
Theorem 11.
Let M be a G-graded R-module and . If K is a g-ϕ-2-abs. prim. submodule of M that is not g-2-abs. prim., then .
Proof.
Since K is a g--2-abs. prim. submodule of M that is not g-2-abs. prim., there are and such that , , and . Suppose that . Then there are and such that . By Theorem 10, we get . So, or or . Therefore, or or , which is a contradiction. Hence, . □
4. Conclusions
In this study, we introduced the notions of graded -2-abs. and graded -2-abs. prim. submodules as generalizations of the notions of graded 2-abs. and graded 2-abs. prim. submodules. Several properties of these new types of graded submodules have been given. As a proposal of further work on the topic, we are going to study the concept of graded -r-ideals as a generalization of the concept of graded r-ideals.
Author Contributions
Conceptualization, A.S.A., M.B. and R.A.-D.; methodology, A.S.A., M.B. and R.A.-D.; validation, A.S.A., M.B. and R.A.-D.; investigation, A.S.A., M.B. and R.A.-D.; writing—original draft preparation, A.S.A., M.B. and R.A.-D.; software, A.S.A., M.B. and R.A.-D.; resources, A.S.A., M.B. and R.A.-D.; writing—review and editing, A.S.A., M.B. and R.A.-D. All authors have read and agreed to the published version of the manuscript.
Funding
This research was funded by the Deanship of Scientific Research at Princess Nourah bint Abdulrahman University through the Fast-track Research Funding Program.
Institutional Review Board Statement
Not applicable.
Informed Consent Statement
Not applicable.
Data Availability Statement
Not applicable.
Acknowledgments
The authors gratefully thank the referees for the constructive comments, corrections and suggestions which definitely help to improve the readability and quality of the article.
Conflicts of Interest
The authors declare that they have no conflict of interest.
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