# An Element Weakly Primary to Another Element

Authors: C. S. Manjarekar; U. N. Kandale
Journal: Chinese Journal of Mathematics
 (2013)

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## Abstract

We introduce the concept “An element weakly primary to another element” and using this concept we have generalized some result proved by Manjarekar and Chavan (2004). It is shown that if{bα} is a family of elements weakly primary to a in L, then ⋁αbα is weakly primary to a.


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## Body

## 1. Introduction

Multiplicative lattice is a complete lattice provided with commutative, associative, and join distributive multiplication for which the largest element 1 acts as a multiplicative identity. A proper elementp of L is called prime element if ab⩽p⇒a⩽p or b⩽p for a,b∈L and is called primary element if ab⩽p implies a⩽p or bn⩽p for some n∈Z+. An element a of L is called compact if a⩽∨X, and X⊆L implies the existence of finite number of elements X1,X2,X3,…,Xn of L such that a⩽X1∨X2∨X3∨⋯∨Xn. Throughout this paper, L denotes compactly generated multiplicative lattice with 1 compact and every finite product of compact elements is compact. Let L* be the set of all compact elements in L. Also, (a:b) is the greatest element c in L such that cb⩽a. An element a∈L is join principal if x∨(y:a)=(xa∨y):a and meet principle if x∧ya=((x:a)∧y)a, for all x,y∈L.An element is principle if it is both join and meet principle. Fora∈L, a=∨{x∈L*∣xn⩽aforsomen∈Z+}. An element a∈L is called semiprimary if a is primary element. L is said to satisfy the condition (*) if every semiprimary element is primary element.An elementa∈L is said to be strong join principle element if a is compact and join principle. An element a∈L is p-primary if a is primary and a=p and a∈L is semiprime if a=a. An element a of L is called zero divisor if ∃0≠b∈L such that ab=0, and if L has no zero divisor then L will be called lattice domain or simply a domain. L* denotes the set of compact elements of L.The concept of weakly prime element is studied by Çallialp et al. [1]. The concept of weakly primary element is introduced by Sachin and Vilas [2]. For other definitions and simple properties of multiplicative lattice, one can refer to Dilworth [3].Definition 1.
Weakly primary element is defined as follows.An elementq∈L is said to be a weakly primary element if for a,b∈L*, 0≠ab⩽q implies a⩽q or bn⩽q for some n∈Z+.Example 2.
Lattice of ideals of ringR=〈Z12,+,·〉 (see Figure 1).Figure 1In the lattice of Example2, an element a is weakly primary element. From Definition 1, it is clear that every weakly prime element is weakly primary element Converse need not be true. Since in Example 2,  a is weakly primary element but it is not weakly prime element. Further, if q is a weakly primary element, then q is a weakly prime element. Because if for compact element x and y such that 0≠xy⩽q then xnyn=(xy)n⩽q for some n∈Z+. As q is a weakly primary element, either xn⩽q or (yn)m=ynm⩽q for some n∈Z+. Consequently, x⩽q or y⩽q. Thus, q is a weakly prime element. This implies that every weakly primary element is a weakly semiprimary element. It need not be true that a is always weakly prime or a is always weakly semiprimary. In Example 2, the least element 0 is not semiprimary as 0=b is not a weakly prime element. The concept of “An element prime  to another element” is introduced in [4]. An element b∈L is prime  to an element a if for x∈L, xb⩽a implies x⩽a.Now, we define the following.Definition 3.
An element weakly prime to another element is defined as follows.
An element,b∈L, is called weakly prime to an element a∈L if for any x∈L, 0≠xb⩽a implies x⩽a.
In Example2, the element d is weakly prime to an element c, but d is not weakly prime to any other element of L. This follows directly from the fact that an element y is weakly prime to an element x if and only if x:y=x.


## 2. An Element Weakly Primary to Another Element

Now we introduce the following main concept which is a generalization of the concept introduced by Manjarekar and Chavan [5].Definition 4.
An elementb is said to be weakly primary to another element a in L if for x∈L*, 0≠xb⩽a implies xn⩽a for some n∈Z+.In Example2, the element b is weakly primary to a, but note that b is not weakly prime to a. This follows directly from Corollary 9, and note that (a:b)=c=a and a<c. Evidently, if b is weakly prime to a, then b is weakly primary to a in L. Now if p is a weakly prime element and ap, then a is weakly prime to p, and if q is a weakly primary element and a compact element aq, then a is a weakly primary element to q.Thus, from this, it is clear that elements weakly primary to another element exist in the latticeL. Since L is compactly generated multiplicative lattice with 1 compact, weakly prime element and hence weakly primary element exists in L. Hereafter, L will be a domain. We prove some interesting results including characterizations.Theorem 5.
No proper nonzero element is weakly prime or weakly primary to itself inL.Proof.
Ifa is a proper nonzero element in L and a is weakly primary to a itself, then 0≠a.1=a implies that 1=a, a contradiction. Therefore, no proper nonzero element is weakly prime or weakly primary to itself in L.Now we prove some characterizations of an element weakly primary toa.Theorem 6.
Leta∈L be a semiprime element. Then 0≠b is weakly primary to a if and only if b is weakly prime to a.Proof.
Assume thatb is weakly primary to a semiprime element a. Let 0≠xb⩽a for some x∈L*. Then xn⩽a for some n∈Z+. Consequently, x⩽a. As a is semiprime, x⩽a. Thus, b is weakly prime to a. The converse part is obvious.Theorem 7.
LetL be a lattice domain. Let a,b∈L; then 0≠b is weakly primary to a if and only if (a:b)⩽a.Proof.
Assume that0≠b is weakly primary to a. Let 0≠x∈L* such that 0≠x⩽(a:b); then, 0≠xb⩽a. As b is weakly primary to a,xn⩽a for some n∈Z+. Hence, x⩽a. This shows that (a:b)⩽a.
Conversely, assume that(a:b)⩽a. Let 0≠xb⩽a for some x∈L*. Then, we have x⩽(a:b)⩽a. This implies that xn⩽a for some n∈Z+. Thus, b is weakly primary to a.Theorem 8.
LetL be a lattice domain. Let a,b∈L; then 0≠b is weakly prime to a if and only if a=(a:b).Proof.
Assume that0≠b is weakly prime to a in L. Let 0≠x∈L such that x⩽(a:b). Then 0≠xb⩽a. As b is weakly prime to a, we have x⩽a. This shows that (a:b)⩽a. But a⩽(a:b). Therefore, we get a=(a:b).
Conversely, assume that(a:b)=a. Let, 0≠xb⩽a for x∈L. Then, we get x⩽(a:b)=a. Thus b is weakly prime to a.Corollary 9.
LetL be a lattice domain. Let, a,b∈L. Then, 0≠b is weakly primary to a but it is nonweakly prime to a if and only if a<(a:b)⩽a.Proof.
It follows from the fact thata⩽(a:b) and from Theorems 7 and 8.Corollary 10.
Leta,b∈L. If a is weakly semiprimary element and ba, then 0≠b is weakly primary to a.Proof.
Assume thata∈L is a weakly semiprimary element and ba. Let x∈L* such that 0≠xb⩽a. Then 0≠xb⩽a. As a is a weakly prime element and ba, we have x⩽a. This implies that xn⩽a for some n∈Z+. Thus, b is weakly primary to a.Theorem 11.
LetL be a lattice domain. Let a,b∈L. Then, 0≠b is weakly prime to a if and only if b is weakly prime to (a:x) for every 0≠x∈L.Proof.
Assume thatb is weakly prime to a in L. Let 0≠yb⩽(a:x) for some y∈L. Then, 0≠xyb⩽a. As b is weakly prime to a, xy⩽a. Consequently, y⩽(a:x). Thus, b is weakly prime to (a:x) for every 0≠x∈L. The converse is obvious, since, if b is weakly prime to (a:x) for every 0≠x∈L, b is weakly prime to (a:1)=a.Theorem 12.
Leta,b∈L and let L be a lattice domain. If b is weakly primary to a and a is a semiprime element in L, then b is weakly primary to (a:x) for every x∈L.Proof.
It follows from Theorems6 and 11.Theorem 13.
Leta,b∈L. Then 0≠b is weakly primary to a in L if and only if each x⩾a is weakly primary to a.Proof.
Assume that0≠b is weakly primary to a in L. Let x⩾b and yx⩽a for some y∈L*. Then 0≠yb⩽a. Therefore, by assumption, yn⩽a for some n∈Z+.
This shows that eachx⩾b is weakly prime to a. The converse part is obvious.Theorem 14.
If{bα} is a family of a elements weakly primary to a in L, then ⋁αbα is weakly primary to a.Proof.
It follows from the fact thatbα⩽⋁αbα and from Theorem 13.Theorem 15.
Leta,b∈L. Then, 0≠b is nonweakly primary to a if and only if each x⩽b is nonweakly primary to a.Proof.
Assume thatb is nonweakly primary to a. Therefore, by Theorem 8, we have a:ba. Let x be an element of L such that x⩽b. Then (a:b)⩽(a:x). This shows that (a:x)a. Thus, again by Theorem 8, each x⩽b is nonweakly primary to a.This lemma leads us to the following two obvious corollaries.Corollary 16.
If{bα} is a family of elements nonweakly primary to a in L, then ⋀αbα is nonweakly primary to a.Corollary 17.
If⋁αbα is nonweakly primary to a in L, then each bα is nonweakly primary to a.Theorem 18.
If y is compact and0≠xy is nonweakly primary to a, then either x is nonweakly primary to a or yn is nonweakly primary to a for some n∈Z+.Definition 19.
Completely meet semiprimary elements are defined as follows.
An elementa is said to be completely meet semiprimary element if a is a completely meet prime element.Example 20.
Every elementx<d is not a completely meet prime element. But note that x=d. Thus, each x<d is a completely meet semiprimary element (see Figure 2).Figure 2Result 1.
In any multiplicative latticeS, we have ⋀α(a:xα)=a:(⋁αxα) for any a,xα∈S.Theorem 21.
Suppose thata is a completely meet semiprimary element of L and let {bα}⊆L. If each 0≠bα is nonweakly primary to a in L, then ⋁αbα is nonweakly primary to a.Proof.
By Result1, we have a:(⋁αbα)=⋀α(a:bα). But each 0≠bα is nonweakly primary to a. Consequently, by Theorem 12, each (a:bα)a. As a is completely meet semiprimary element, ⋀α(a:bα)=a:(⋁αbα)a. Therefore, by Theorem 8, ⋁αbα is nonweakly primary to a.Now we construct a new element as follows. Defineqa=∨{x∈L∣xisnonweaklyprimarytoa}.Theorem 22.
Ifa is a completely meet semiprimary element, then qa is weakly primary element and is nonweakly primary to a.Proof.
By Theorem21, it follows that qa is nonweakly primary element to a. Let x and y be compact elements such that, 0≠xy⩽qa. Then by Theorem 15, xy is nonweakly primary to a. Therefore, by Theorem 18, either x is nonweakly primary to a or yn is nonweakly primary to a for some n∈Z+. Thus, x⩽qa or yn⩽qa for some n∈Z+. This shows that qa is a weakly primary element.



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