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, and -      graded 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. Then -      graded 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), and -      graded 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 . 
   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, .    □