1. Introduction
The motivation for this paper lies in an attempt to extend in some way the famous results due to Posner [
46], Vukman [
48] and Ali-Dar [
6]. A number of authors have generalized these theorems in several ways (see, for example, [
16,
20,
33,
35,
39,
42,
50,
51], where further references can be found). Throughout this article,
will represent an associative ring with center
. The standard polynomial identity
in four variables is defined as
where
is
or
according to
being an even or odd permutation in symmetric group
. For any
, the symbol
stands for commutator, while the symbol
will stand for the anti-commutator
. The higher order commutator is define as follows: for any
,
and inductively, we write
, (where
is a fixed integer), is called commutator of order
k or simply
-commutator. It is also known as Engel condition in literature (viz.; [
35]). Analogously, we define the higher order anit-commutator, and set
and inductively, we set
for
is called anti-commutator of order
“Recall that a ring
is called prime if, for
,
implies
or
By a prime ideal of a ring
, we mean a proper ideal
and for
,
implies that
or
. We note that for a prime ring
,
is the prime ideal of
and
is a prime ring. An ideal
of a ring
is called semiprime if it is the intersection of prime ideals or alternatively, if
implies that
for any
A ring
is said to be
n-torsion free if
,
implies
. An additive mapping
satisfying
and
is called an involution. A ring equipped with an involution is known as ring with involution or *-ring. An element
ℓ in a ring with involution * is said to be hermitian if
and skew-hermitian if
. The sets of all hermitian and skew-hermitian elements of
will be denoted by
and
, respectively. If
is 2-torsion free then every
can be uniquely represented in the form
where
and
. The involution is said to be of the first kind if
, otherwise it is said to be of the second kind. We refer the reader to [
32] for justification and amplification for the above mentioned notations and key definitions.
A map
is a derivation of a ring
if
e is additive and satisfies
for all
. A derivation
e is called inner if there exists
such that
for all
An additive map
is called a generalized derivation if there exists a derivation
e of
such that
for all
(see [
14] for details). For a nonempty subset
S of
, a mapping
is called commuting (resp. centralizing) on
S if
(resp.
for all
. The study of commuting and centralizing mappings goes back to 1955 when Divinsky [
31] proved that a simple artinian ring is commutative if it has a commuting automorphism different from the identity mapping. Two years later Posner [
46] showed that a prime ring must be commutative if it admits a nonzero centralizing derivation. In 1970, Luh [
38] generalized Divinsky’s result for prime rings. Later Mayne [
44] established the analogous result of Posner for nonidentity centralizing automorphisms. The culminating results in this series can be found in [
19,
20,
21,
33,
35,
43] and [
48,
49]. In [
48], Vukman generalized Posner’s second theorem for second order commutator and established that if a prime ring of characteristic different from 2 admits a nonzero derivation
e such that
for all
, then
is commutative. Most classical and elegant generalization of Posner’s second theorem is due to Lanski [
34]. Precisely, he proved that if a prime ring
admits a nonzero derivation
e such that
for all
, where
L is a non-commutative Lie ideal of
and
a fixed integer, then
and
for a field
F. These results have been extended in various ways (viz; [
3,
23,
26,
30,
50,
51] and references therein). The goal of this paper is to study these results in the setting of arbitrary rings with involution involving prime ideals and describe the structure of a quotient ring
where
is an arbitrary ring and
is a prime ideal of
.
Let
be a ring with involution * and
S be a nonempty subset of
. Following [
6,
25], a mapping
of
into itself is called *-centralizing on
S if
for all
in the special case where
for all
the mapping
is said to be *-commuting on
S. In [
6,
25], the first author together with Dar initiated the study of these mappings and proved that the existence of a nonzero *-centralizing derivation of a prime ring with second kind involution forces the ring to be commutative. Apart from the characterizations of these mappings of prime and semiprime rings with involution, they also proved *-version of Posner’s second theorem and its related problems. Precisely, they established that : Let
be a prime ring with involution * such that
. Let
e be a nonzero derivation of
such that
for all
and
Then
is commutative. Futher, they showed that every
-commuting map
on semiprine ring with involution of characteristic different from two is of the form
for all
(the extended centroid of
and
is an additive mapping. In the sequel, recently Nejjar et al. [
42, Theorem 3.7] established that if a 2-torsion free prime ring with involution of the second kind admits a nonzero derivation
e such that
for all
then
is commutative. In 2020, Alahmadi et al. [
2] extend the above mentioned result for generalized derivations. Over the last few years the interest on this topic has been increased and numerous papers concerning these mappings on prime rings have been published (see [
1,
2,
7,
8,
9,
10,
13,
39,
42,
45] and references therein). In [
24], Creedon studied the action of derivations of prime ideals and proved that if
e is a derivation of a ring
and
is a semiprime ideal of
such that
is characteristic-free and
, then
for some positive integer
k.
In view of the above observations and motivation, the aims of the present paper is to prove the following main theorems.
Theorem-A Let be a ring with involution * of the second kind and a prime ideal of such that . If and are derivations of such that for all , then one of the following holds:
Theorem-B Let be a ring with involution * of the second kind and a prime ideal of such that . If and are derivations of such that for all , then one of the following holds:
Theorem-C Let be a ring with involution * of the second kind and a prime ideal of such that . If admits a derivation e such that for all then one of the following holds:
Theorem-D Let be a ring with involution * of the second kind and a prime ideal of such that . If admits a derivation e such that for all then one of the following holds:
Theorem-E Let be a 2-torsion free semiprime ring with involution * of the second kind. If admits a nonzero *-centralizing derivation for all then contains a nonzero central ideal.
In view of
-centralizing mappings, Theorem-
e and Theorem-
E recognized as the
-versions of well known theorems due to Posner [
46] and Vukman [
48]. As the applications of Theorems
A to
E just mentioned above, we extends and unify several classical theorems proved in [
6,
7,
25,
42,
46] and [
48,
49]. Since these results are in new direction, so there are various interesting open problems related to our work. Hence, we conclude our paper with a direction for further research in this new and exciting area of theory rings with involution.
We shall do a great deal of calculation with commutators and anti-commutators, routinely using the following basic identities: For all
2. Preliminary Results
Let
be
-ring. Following [
8,
47], an additive mapping
is called a *-derivation of
if
for all
An additive mapping
is called a Jordan *-derivation of
if
for all
In [
21], Brešar showed that if a prime ring
admit nonzero derivations
and
of
such that
for all
where
I is a nonzero left ideal of
, then
is commutative. Further, this result was extended by Argac [
12] as follows: Let
be a semiprime ring and
are derivations of
such that at least one is nonzero. If
for all
, then
contains a nonzero central ideal. Motivated by the above mentioned results, first author together with Alhazmi et al. [
10] studied more general problem in the setting of rings with involution. Prescisely, they proved that if a
-torsion free prime ring with involution of the second kind admit Jordan *-derivations
e and
g of
such that
for all
(where
m and
n are fixed positive integers), then
or
is commutative. In the sequel, very recently Nejjar et al. [
42, Theorem 3.7] established that if a 2-torsion free prime ring with involution of the second kind admits a nonzero derivation
e such that
for all
then
is commutative. The goal of this section is to initiate the study of a more general concept than *-centralizing mappings are; that is, we consider the situation when the mappings
and
of a ring
satisfy
for all
where
is an arbitrary ring and
is a prime ideal of
. Precisely, we prove the following theorem.
Theorem 1. Let be a ring with involution * of the second kind and a prime ideal such that . If and are derivations of such that for all , then one of the following holds:
Following are the immediate consequences of Theorem 1. In fact, Corollary 1 is in sprit of the result due to Posner’s second theorem.
Corollary 1. Let be a ring with involution * of the second kind and a prime ideal of such that . If admits a derivation e such that for all , then one of the following holds:
Corollary 2. Let be a ring with involution * of the second kind and a prime ideal of such that . If admits a derivation e such that for all , then one of the following holds:
.
Corollary 3. Let be a prime ring with involution * of the second kind such that . If admits a *-commuting derivation e, then or is a commutative integral domain.
Corollary 4. Let be a prime ring with involution * of the second kind such that . If admits a derivation e such that for all , then .
For the proof of Theorem 1, we need the following lemmas, some of which are of independent interest. We begin our discussions with the following.
Lemma 1. [5, Lemma 2] Let be a ring, be a prime ideal of . If e is a derivation of satisfying the condition for all , then or is a commutative.
Lemma 2. [41, Lemma 1] Let be a ring, a prime ideal of , and derivations of . Then for all if and only if and ) or is a commutative integral domain."
Lemma 3. Let be a ring with involution * of the second kind and a prime ideal of such that . If for all , then one of the following holds:
Proof. We assume that
. By the assumption, we have
for all
. Direct linearization of relation (
1) gives
for all
. Replacing
ℓ by
in (
2), where
, we get
for all
. Since
, it follows that
for all
. Combining (
2) and (
3), we obtain
for all
. This implies that
for all
. Since elements of
are cosets and notice that
implies
Therefore, the above equation gives
for all
and hence, we infer that
for all
. This can be written as
for all
. This implies that
is commutative. Now we show that
is integral domain. We suppose that
for all
. This is equivalent to the expression
for all
. This implies that
for all
. For any
, we have
for all
. This gives
. Hence,
. Thus, we get
or
. This further implies that
or
. This shows that
is an integral domain. Consequently, we conclude that
is a commutative integral domain. This proves the lemma. □
In view of Lemmas , we conclude the following result.
Lemma 4. Let be a ring, be a prime ideal of . If e is a derivation of satisfying the condition for all , then or is a commutative integral domain.
We are now ready to prove our first main theorem.
Proof of Theorem 1. We assume that
. By the assumption, we have
Replacing
ℓ by
in (
9), where
, we get
Application of (
9) yields
Replace
h by
in (
10), where
, to get
Substituting
in place of
ℓ in (
9), where
, we arrive at
for all
. From (
9), we have
Adding (
12) and (
13), we obtain
this impels
for all
. Using (
11) in (
14), we have
Since
and
, we have
In particular, for , we get for all Therefore, from Lemma 2, we conclude that ( and ) or is a commutative integral domain.□
Corollary 5. Let be a prime ring with involution * of the second kind such that . If admit derivations and such that for all , then or is a commutative integral domain.
We now prove another theorem in this vein.
Theorem 2. Let be a ring with involution * of the second kind and a prime ideal of such that . If admits a derivation e such that for all , then one of the following holds:
Proof. Suppose that
. By the assumption, we have
for all
. First we assume that
. Then, result follows by Lemma 3. Henceforward, we suppose that
. Linearizing (
16), we get
for all
. Replacing
ℓ by
in (
17), where
, we get
for all
. Replacing
h by
in the last relation, where
and using the hypotheses, we arrive at
for all
. Replacing
ℓ by
in (
17), where
, we find that
for all
. Using (
18) and the condition
in (
19), we obtain
for all
. Addition of (
17) and (
20) gives that
for all
. This implies
for all
. In particular, for
, we have
for all
. In view of Lemma 4, we conclude that
is a commutative integral domain. □
The following result is interesting in itself.
Theorem 3. Let be a ring with involution * of the second kind and a prime ideal of such that . If and are derivations of such that for all , then one of the following holds:
Proof. Assume that
. By the assumption, we have
for all
. We divide the proof in three cases.
Case (i): First we assume that
. Then, relation (
21) reduces to
for all
. In view of Theorem 2, we get the required result.
Case (ii): Now we assume that
. Then, relation (
21) reduces to
for all
. This can be further written as
for all
. If
, then result follows by Lemma 3. Henceforward, we suppose that
. Linearizing (
22), we get
for all
. Replacing
ℓ by
in (
23), where
, we get
for all
This implies that
for all
Replacing
h by
in the last relation, where
, we arrive at
for all
Since
, the last relation gives
for all
Replacing
ℓ by
in (
23), where
, we find that
for all
. Left multiplying in (
23) by
k, we obtain
for all
Combining (
25) and (
26), we get
for all
. Replacing
by
in (
27) and using (
24), where
, we get
for all
. Using the assumption
, we find that
for all
. Application of the primeness of
yields
or
. The first case
implies
, which gives a contradiction. Thus, we have
for all
. In particular for
, we have
for all
Therefore, in view of Lemma 4, we conclude that
is a commutative integral domain.
Case (iii): Finally, we assume that
and
. Then direct linearization of (
21) gives
for all
. Replacing
ℓ by
in (
29), where
and using it, we get
for all
. Replacing
ℓ by
in (
30), where
, we obtain
for all
. Combination of (
30) and (
31) yields that
which implies
Replacing
h by
in the last relation and using the hypotheses of theorem, we get
This implies either
or
If
, then by Lemma 3,
is a commutative integral domain. On the other hand, we have
. Similarly, we can find
. Writing
instead of
ℓ in (
29), where
and using the fact that
, we arrive at
for all
Comparing (
29) and (
32), we obtain
Now, replacing
ℓ by
in the above expression, we obtain
In particular, for we have for all . This gives for all . The primeness of infers that or . Set and . Clearly, A and B are additive subgroups of such that But, a group cannot be written as a union of its two proper subgroups, consequently or The first case contradicts our suppostion that Thus, we have for all . Therefore, in view of Lemma 3, is a commutative integral domain. This completes the proof of theorem. □
Using similar approach with necessary variations, one can establish the following result.
Theorem 4. Let be a ring with involution * of the second kind and a prime ideal of such that . If and are derivations of such that for all , then one of the following holds:
In view of Theorems 3 & 4, we have the following corollaries:
Corollary 6. Let be a prime ring with involution * of the second kind such that . If admit derivations and such that for all , then is a commutative integral domain.
Corollary 7. Let be a ring with involution * of the second kind and a prime ideal of such that . If admits a derivation e such that for all , then one of the following holds:
Corollary 8. Let be a ring with involution * of the second kind and a prime ideal of such that . If admits a derivation e such that for all , then one of the following holds:
Corollary 9 ([
25], Theorem
).
Let be a prime ring with involution * of the second kind such that . If admits a derivation e such that for all , then is a commutative integral domain.
We leave the open question whether or not the assumption
(where
is prime ideal of an arbitray ring
) can be removed in Theorems 1 and 3. In view of Theorem 1 and Theorem
of [
10], we conclude this section with the following conjecture.
Conjecture: Let m and n be fixed positive integers. Next, let be a -ring with suitable torsion restrictions and be a prime ideal of . If admit Jordan *-derivations e and g of such that for all . Then, what we can say about the structure of and the forms of
3. Derivations act as homomorphisms and anti-homomorphisms on prime ideals
Ring homomorphisms are mappings between two rings that preserve both addition and multiplication. In particular, we are concerned with ring homomorphisms between two rings. If
is the real number field, then the zero map and the identity are typical examples of ring homomorphisms on
Let
S be a nonempty subset of
and
e a derivation on
. If
or
for all
, then
e is said to be a derivation which acts as a homomorphism or an anti-homomorphism on
S, respectively. Of course, derivations which acts as an endomorphisms or anti-endomorphisms of a ring
may behave as such on certain subsets of
, for example, any derivation
e behaves as the zero endomorphism on the subring
T consisting of all constants (i.e., elements
ℓ for which
). In fact, in a semiprime ring
,
e may behave as an endomorphism on a proper ideal of
. As an example of such
and
e, let
S be any semiprime ring with a nonzero derivation
, take
and define
e by
. However in case of prime rings, Bell and Kappe [
18] showed that the behaviour of
e is some what more restricted. By proving that if
is a prime ring and
e is a derivation of
which acts as a homomorphism or an anti-homomorphism on a nonzero right ideal of
, then
on
. Further, Ali et al. obtained [
4] the above mentioned result for Lie ideals. Recently, Mamouni et al. [
40] studied the above mentioned problem for prime ideals of an arbitrary ring by cosidering the identity
for all
or
for all
where
is prime ideal of
. In the present section, our objective is to extend the above study in the setting of rings with involution involving prime ideals. In fact, we prove the following result:
Theorem 5. Let be a ring with involution * of the second kind and a prime ideal of such that . If admits a derivation e such that for all then one of the following holds:
Proof. Assume that
By the hypothesis, we have
for all
. Linearization of (
33) gives that
for all
. Replacing
ℓ by
in (
34), where
, we get
for all
. Taking
in (
35), where
and using the hypotheses of theorem, we obtain
for all
. Invoking the primeness of
yields that
or
for all
Consider the case when
for all
. Replacing
ℓ by
in (
36) and combining with the obtained relation, we get
for all
This implies that
for all
In particular for
, where
, we have
for all
. Substituting
for
in the last relation, we obtain
. This yields
for all
. Since
is a prime ideal of
, we have
On the other hand, consider the case
. Replacing
ℓ by
in (
34), where
, we get
Combination of (
34) and (
38) gives that
for all
. This implies that
for all
. Taking
in the above relation and using
, we get
for all
Since
, one can conclude that
. □
Applying an analogous argument, we have the following result.
Theorem 6. Let be a ring with involution * of the second kind and a prime ideal of such that . If admits a derivation e such that for all then one of the following holds:
.
Corollary 10. Let be a prime ring with involution * of the second kind such that . If admits a derivation e such that or for all , then .
Theorem 7. Let be a 2-torsion free semiprime ring with involution * of the second kind. If admits a derivation e such that for all then
Proof. Assume that
By the assumption, we have
By the semiprimeness of
, there exists a family
of prime ideals such that
(see [
11] for details). For each
in
, we have
Invoking Theorem 5, we conclude that Consequently, we get and hence result follows. Thereby the proof is completed. □
Analogusly, we can prove the following result.
Theorem 8. Let be a 2-torsion free semiprime ring with involution * of the second kind. If admits a derivation e such that for all then
4. Applications
In this section, we present some applications of the results proved in Section
Vukman [
48, Theorem 1] generalizes the classical result due to Posner (Posner’s second theorem) [
46] and proved that if
e is a derivation of a prime ring
of characteristic different from 2, such that
for all
then
or
is commutative. In fact, in view of Posner’s second theorem, he merely showed that
e is commuting, that is,
for all
In [
29], Deng and Bell extended the above mentioned result for semiprime ring and established that if a 6-torsion free semiprime ring admits a derivation
e such that
for all
with
where
I is a nonzero left ideal of
then
contains a nonzero central ideal. These results were further refined and extended by a number of algebraists (see for example, [
3,
23,
26,
30,
33,
36] and [
50]). It is our aim in this section to study and extend Vukman’s and Posner’s results for arbitrary rings with involution involving prime ideals. In fact, we prove the *-versions of these theorems. Moreover, our approach is somewhat different from those employed by other authors. Precisely, we prove the following result.
Theorem 9. Let be a ring with involution * of the second kind and a prime ideal of such that . If admits a derivation e such that for all then one of the following holds:
A derivation
is said to be
-centralizing if
for all
. The last expression can be written as
for all
. Consequently, Theorem 9 regarded as the
-version of Vukman’s theorem [
48]. Applying Theorem 9, we also prove that if a 2-torsion free semiprime ring
with involution * of the second kind admiting a nonzero *-centralizing derivation, then
must contains a nonzero central ideal. In fact, we prove the following result.
Theorem 10. Let be a 2-torsion free semiprime ring with involution * of the second kind. If admits a nonzero *-centralizing derivation for all then contains a nonzero central ideal.
As an immediate consequence of Theorem 10, we obtain the following result.
Corollary 11. Let be a 2-torsion free semiprime ring with involution * of the second kind. If admits a nonzero *-commuting derivation for all then contains a nonzero central ideal.
In order to prove of Theorem 10, we need the proof of Theorem 9.
Proof of Theorem 9. Assume that
. By the hypothesis, we have
A linearization of (
39) yields that
for all
Putting
in (
40), we get
for all
Combining (
40) and (
41), we obtain
for all
Replacing
by
in (
42), where
we deduce that
Taking
, where
and using the hypothesis, we have
Now, substituting
in place of
in (
42), where
, we get
for all
Application of (
43) and the condition
yields
for all
From (
42) and (
44), we can obtain
Writing
instead of
ℓ, we get
Replacing
z by
in (
45), we find that
In particular for
, we have
Since is a prime ideal of , we have for all or for all . Let us set and . Clearly, A and B are additive subgroups of whose union is . But a group cannot be written as a union of its two proper subgroups, it follows that either or In the first case, is a commutative integral domain from Lemma 3. On the other hand, if for all , then we get for all Hence, in view of Corollary 1, we conclude that or is a commutative integral domain. This completes the proof of theorem. □
Proof of Theorem 10. We are given that
is *-centralizing derivation, that is,
for all
. This implies that
for all
. This gives
In view of semiprimeness of
, there exists a family
of prime ideals such that
(see [
11] for more details). Let
denote a fixed one of the
. Thus, we have
From the proof of Theorem 9, we observe that for each
either
or
Define
to be the set of
for which
holds and
the set of
for which
holds. Note that both are additive subgroups of
A and their union is equal to
A. Thus either
or
, and hence
satisfies one of the following:
or
Call a prime ideal in
a type-one prime if it satisfies
, and call all other members of
type-two primes. Define
and
respectively as the intersection of all type-one primes and the intersection of all type-two primes, and note that
Clearly, from both the cases, we can conclude that
for all
for all
This implies that
for all
. That is,
for all
Hence, in view of [
19],
contains a nonzero central ideal.□
Jordan product version of Theorem 9 is the following.
Theorem 11. Let be a ring with involution * of the second kind and a prime ideal of such that . If admits a derivation e such that for all then one of the following holds:
.
Proof. Assume that
. By the hypothesis, we have
A linearization of (
47) yields that
for all
Putting
in (
48), we get
for all
Combining (
48) and (
49), we obtain
for all
Substitution of
for
in (
50), where
produce that
Taking
, where
and using the hypothesis, we have
Next, substitute
in place of
in (
50), where
, we get
for all
Application of (
51) and the condition
yields
for all
From (
50) and (
52), we can obtain
That is,
for all
A linearization for
ℓ in (
53) yields that
for all
. Replacing
ℓ by
in (
54), we have
which can be written as
Replacing
ℓ by
in the last relation, we have
Application of (
55) gives that
The above relation is same as (
46). Therefore using the same arguments as we have used after (
46), we get
or
is a commutative integral domain. If
, then proof is done. On the other hand, if
is a commutative integral domain, then (
54) reduces as
Since
, the above relation becomes
The primeness of forces that . Thus the proof is completed now. □
The following results are immediate corollaries of Theorems 9 & 10.
Corollary 12. Let be a ring with involution * of the second kind and a prime ideal of such that . If admits a derivation e such that for all then one of the following holds:
Corollary 13. [42, Theorem 3.7] Let be a prime ring with involution * of the second kind such that . If admits a derivation e such that for all , then or is a commutative integral domain.
Corollary 14. Let be a prime ring with involution * of the second kind such that . If admits a derivation e such that for all , then .
Theorem 12. Let be a 2-torsion free semiprime ring with involution * of the second kind. If admits a derivation e such that for all , then .
Proof.
By the semiprimeness of
, there exists a family
of prime ideals such that
. For each
in
, we have
Application of Theorem 11 gives that Thus, and hence Thereby the proof is completed. □
We feel that Theorem 9 (resp. Theorem 11) can be proved without the assumption for any prime ideal of an arbitray ring , but unfortunately we are unable to do it. Hence, Theorem 9 leads the following conjecture.
Conjecture: Let be a ring with involution * of the second kind and a prime ideal of . If admits a derivation e such that for all then one of the following holds:
5. A direction for further research
Throughout this section, we assume that
and
n are fixed positive integers. Several papers in the literature evidence how the behaviour of some additive mappings is closely related to the structure of associative rings and algebras (cf.; [
2,
6,
9,
16,
20,
21][
28,
30,
33] and [
39]. A well-known result proved by Posner’s [
46] states that a prime ring must be commutative if
for all
where
e is a nonzero derivation of
. In [
48,
49], Vukman extended Posner’s theorem for commutators of order 2, 3 and described the structure of prings rings whose characteristic is not two and satisfying
for every
The most famous and classical generalization of Posner’s and Vukman’s results are the following theorem due to Lanski [
35] for
-commutators:
Theorem 13. [
35]
Let and k are fixed positive integers and is prime ring. If a derivation e of satisfies for all , where I is a nonzero left ideal of , then or is commutative.
In [
37], Lee and Shuie studied that if a noncommutative prime ring
admitting a derivation
e such that
for all
, where
I is a non zero left ideal, then
except when
. In the year 2000, Carini and De Filippis [
23] studied Posner’s classical result for power central values. In particular, they discussed this situation for
of characteristic not two and proved that if
for all
, a noncentral Lie ideal of
, then
satisfies
. In 2006, Wang and You [
51] mentioned that the restriction of characteristic need not necessary in Theorem 1.1 of [
23]. More precisely, they proved the following result.
Theorem 14. Let be a noncommutative prime ring and L be a noncentral Lie ideal of . If admits a derivation e satisfies for all , then satisfies the standard identity in 4 variables.
Motivated by these two results, Wang [
50] studied the similar condition for
of characteristic not two and obtained the same conclusion. In fact, he proved the following results.
Theorem 15. Let be a noncommutative prime ring of characteristic not two. If admits a nonzero derivation e satisfies for all , then satisfies the standard identity in 4 variables.
In our main results (Theorems 1, 3, 5, 9 and 10), we investigate the structure of the qutiont rings where is an arbitrary ring and is a prime ideal of . Nevertheless, there are various interesting open problems related to our work. In this final section, we will propose a direction for future further research. In view of the above mentioned results and our main theorems, the following problems remains unanswered.
Problem 1. Let be a ring of suitable characteristic with involution * of the second kind and a prime ideal of such that . Next, let be a mapping satisfying or for all Then, what we can say about the structure of and
Problem 2. Let be a ring of suitable characteristic with involution * of the second kind and a prime ideal of such that . Next, let be a derivation satisfying or for all Then, what we can say about the structure of and
Problem 3. Let be a ringof suitable characteristic with involution * of the second kind and a prime ideal of such that . Next, let be a derivation satisfying or for all Then, what we can say about the structure of and
Problem 4. Let be a ring of suitable characteristic with involution * of the second kind and a prime ideal of such that . Next, let be a derivation satisfying or for all Then, what we can say about the structure of and