Abstract
Skew continuous morphisms of ordered lattice semirings and ringoids are studied. Different associative semirings and non-associative ringoids are considered. Theorems about properties of skew morphisms are proved. Examples are given. One of the main similarities between them is related to cones in algebras of non locally compact groups.
Mathematics Subject Classification 2010:
08A99; 16Y60; 17A01; 17D99; 22A26; 22A30
1. Introduction
Semirings, ringoids, algebroids and non-associative algebras play important role in algebra and among them ordered semirings and lattices as well [1,2,3,4,5,6,7,8]. This is also motivated by idempotent mathematical physics naturally appearing in quantum mechanics and quantum field theory (see, for example, [9] and references therein). They also arise from the consideration of algebroids and ringoids associated with non locally compact groups. Namely, this appears while the studies of representations of non locally compact groups, quasi-invariant measures on them and convolution algebras of functions and measures on them [10,11,12,13]. The background for this is A. Weil’s theorem (see [14]) asserting that if a topological group has a quasi-invariant σ-additive non trivial measure relative to the entire group, then it is locally compact. Therefore, it appears natural to study inverse mapping systems of non locally compact groups and their dense subgroups. Such spectra lead to structures of algebroids and ringoids. Investigations of such objects are also important for making advances in representation theory of non locally compact groups.
In this paper methods of categorial topology are used (see [15,16,17,18] and references therein).
This article is devoted to ordered ringoids and semirings with an additional lattice structure. Their continuous morphisms are investigated in Section 3. Preliminaries are given in Section 2. Necessary definitions 2.1–2.4 are recalled. For a topological ringoid K and a completely regular topological space X new ringoids are studied, where consists of all continuous mappings with point-wise algebraic operations. Their ideals, topological directed structures and idempotent operations are considered in Lemmas 2.6, 2.8, 2.9, 2.12 and Corollary 2.7. There are also given several examples 2.13–2.18 of objects. One of the main examples between them is related to cones in algebras of non locally compact groups. Another example is based on ordinals. Construction of ringoids with the help of inductive limits is also considered.
Structure and properties of these objects are described in Section 3. Definitions of morphisms of ordered semirings and some their preliminaries are described in Subsection 3.1. An existence of idempotent K-homogeneous morphisms under definite conditions is proved in Lemma 3.4. A relation between order preserving weakly additive morphisms and non-expanding morphisms is given in Lemma 3.7. An extension of an order preserving weakly additive morphism is considered in Lemma 3.9.
Then a weak* topology on a family of all order preserving weakly additive morphisms on a Hausdorff topological space X with values in K is taken. The weak* compactness of under definite conditions is proved in Theorem 3.10. Further in Proposition 3.11 there is proved that and are closed in , where denotes the set of all idempotent K-valued morphisms, also denotes its subset of idempotent homogeneous morphisms.
Categories related to morphisms and ringoids are presented in Subsection 3.2. An existence of covariant functors, their ranges and continuity of morphisms are studied in Lemmas 3.14, 3.16, 3.21, 3.34 and Propositions 3.15, 3.22. In Propositions 3.24, 3.26 and 3.29 such properties of functors as being monomorphic and epimorphic are investigated. Supports of functors are studied in Proposition 3.31. Moreover, in Proposition 3.32 it is proved that definite functors preserve intersections of closed subsets. Then functors for inverse systems are described in Proposition 3.33. Bi-functors preserving pre-images are considered in Proposition 3.35. Monads in certain categories are investigated in Theorem 3.38. Exact sequences in categories are considered in Proposition 3.39.
Lattices associated with actions of groupoids on topological spaces are investigated in subsection 3.3. Supports of -invariant semi-idempotent continuous morphisms are estimated in Proposition 3.42, where G is a topological groupoid and T is its representation described in Lemma 3.40. Structures of families of all semi-idempotent continuous morphisms associated with a groupoid G and a ringoid K are investigated in Proposition 3.43 and Theorems 3.44, 3.45.
The main results are Propositions 3.22, 3.24, 3.29, 3.32, 3.33, 3.35, 3.39, 3.43, Theorems 3.38, 3.44 and 3.45. All main results of this paper are obtained for the first time. The obtained results can be used for further studies of such objects, their classes and classification. They can be applied to investigations of non locally compact group algebras also.
2. Ringoids and Lattice Structure
2.1. Preliminaries
To avoid misunderstandings we first present our definitions.
1. Definitions. Let K be a set and let two operations the addition and the multiplication be given so that K is a semigroup (with associative binary operations) or a quasigroup (with may be non-associative binary operations) relative to + and × with neutral elements and so that for each and either the right distributivity for every or the left distributivity for every is accomplished, then K is called a semiring or a ringoid respectively with either right or left distributivity correspondingly. If it is simultaneously right and left distributive, then it is called simply a semiring or a ringoid respectively.
A semiring K (or a ringoid, or a ring, or a non-associative ring) having also a structure of a linear space over a field and such that , , and for each and is called a semialgebra (or an algebroid, or an algebra or a non-associative algebra correspondingly).
A semiring K (or a semialgebra and so on) supplied with a topology on K (or on K and correspondingly) relative to which algebraic operations are continuous is called a topological semiring (or a topological semialgebra and so forth correspondingly).
A set K with binary operations will also be called an algebraic object. An algebraic object is commutative relative to an operation if for each .
An algebraic object K with binary operations is called either directed or linearly ordered or well-ordered if it is such as a set correspondingly and its binary operations preserve an ordering: for each and for every so that and when belong to the same linearly ordered set Z in K.
Henceforward, we suppose that the minimal element in an ordered K is zero.
Henceforth, for semialgebras, non-associative algebras or algebroids A speaking about ordering on them we mean that only their non-negative cones are considered. For non-negative cones K in semialgebras, non-associative algebras or algebroids only the case over the real field will be considered.
2. Definition. A (non-associative) topological algebra or a topological ringoid, etc., we call topologically simple if it does not contain closed ideals different from and K, where .
3. Definition. We consider a directed set K which satisfies the condition:
for each linearly ordered subset A in K there exists a well-ordered subset B in K such that .
4. Definitions. Let K be a well-ordered (or directed satisfying condition 3) either semiring or ringoid (or a non-negative cone in a algebroid over the real field ) such that
for each , where T is a family of subsets of K.
If K is a directed topological either semiring or ringoid, we shall suppose that it is supplied with a topology
so that every set
- and
That is, if a set Z is linearly ordered in K this topology provides the hereditary topology on Z which is not weaker than the interval topology on Z generated by the base , where .
For a completely regular topological space X and a topological semiring (or ringoid) K let denote a semiring (or a ringoid respectively) of all continuous mappings with the element-wise addition and the element-wise multiplication operations for every and .
If K is a directed semiring (or a directed ringoid) and X is a linearly ordered set, (or ) will denote the set of all monotone non-decreasing (or non-increasing correspondingly) maps .
For the space (or or ) we suppose that
a family T of subsets of K contains the family (or or correspondingly) and K satisfies Condition .
5. Remark. For example, the class of all ordinals has the addition and the multiplication operations which are generally non-commutative, associative, with unit elements 0 and 1 respectively, on the right distributivity is satisfied (see Propositions 4.29–4.31 and Examples 1–3 in [19]). Relative to the interval topology generated by the base the class is the topological well-ordered semiring, where . For each non-void set A in there exists (see [20]).
If K is a linearly ordered non-commutative relative to the addition semiring (or a ringoid), then the new operation defines the commutative addition. Then and for every , that is is left and right distributive.
As an example of a semiring (or a ringoid) K in Definitions 4 one can take or , where b is a cardinal number such that . Each segment is compact in , where . Evidently, satisfies Condition 4, since exists for each set E in (see [20]).
Particularly, if a topological space X is compact and is a semiring (or a ringoid) of all continuous mappings , then a family T contains the family of compact subsets , since a continuous image of a compact space is compact (see Theorem 3.1.10 [21]).
It is possible to modify Definition 4 in the following manner. For a well-ordered K without Condition 4 one can take the family of all continuous bounded functions and denote this family of functions by for the uniformity of the notation.
For a directed K satisfying Condition 3 without Condition 4 it is possible to take the family of all monotone non-decreasing (or non-increasing) bounded functions for a linearly ordered set X and denote this family by ( correspondingly) also.
Naturally, has also the structure of the left and right module over the semiring (or the ringoid correspondingly) K, i.e., and belong to for each and . To any element the constant mapping corresponds such that for each . If K is right (or left) distributive, then (or correspondingly) for every .
The semiring (or the ringoid) will be considered directed:
if and only if for each .
Indeed, if , then and according to Condition 4. Then there exists so that and , consequently, and . Thus for each there exists so that and . From and for each and in K it follows that and for each and in .
If and (i.e. ), then we put .
For a mapping its support is defined as usually
, where denotes the closure of A in X when .
Henceforth, we consider cases, when
a topology on X is sufficiently fine so that functions separate points in X, i.e., for each in X there exists f in (or or correspondingly) such that .
The latter is always accomplished in the purely algebraic discrete case.
2.2. Directed Ringoids of Mappings
6. Lemma. If E is a closed subspace in a topological space X, then is an ideal in .
Proof. If and , then and when , consequently, and are contained in E. Moreover, if , then and are contained in E, since and for each , while is open in X. Thus is a semiring (or a ringoid respectively) and and .
7. Corollary. If E is clopen (i.e. closed and open simultaneously) in X, then is an ideal in .
Proof. For a clopen topological subspace E in X one gets isomorphic with , since each has the zero extension on .
8. Lemma. For a linearly ordered set X and a directed semiring (ringoid) K there are directed semirings (or ringoids correspondingly) and .
Proof. The sets and are directed according to Condition 5 with a partial ordering inherited from . Since and for each and in K, then and for each and all either in or . On the other hand, for each there exists so that and (see §5). If and for and each in K, then and , consequently, and are in . Analogously, if , then and are in . But a constant mapping belongs to and . Thus and are directed semirings (or ringoids correspondingly).
9. Lemma. If is a covering of X and is a topology on K satisfying Conditions 3 and 4, then a semiring (or ringoid or a non-negative cone in a algebroid over ) can be supplied with a topology relative to which it is a topological directed (TD) semiring (or a TD ringoid or a TD algebroid respectively).
Proof. Take a topology on with the base formed by the following sets and their finite intersections:
- ,
- ,
- ,
- ,
10. Note. Henceforward, it will be supposed that is supplied with the topology of Lemma 9, while and are considered relative to the topology inherited from . Particularly, if , then it provides the topology of the uniform convergence on .
11. Corollary. If the conditions of Lemma 9 are satisfied and is the family of all subsets in X and a topology on K is discrete, then is the discrete topology on .
12. Lemma. Suppose that the conditions of Lemma 9 are satisfied. Then the functions
- (1)
- and
- (2)
- (3)
- for each either or or .
Proof. Let satisfy Condition . Then the sets and are closed in X, since f and g are continuous functions on X and the topology on K satisfies Condition 4. For each closed set E in K the sets
- and
Relative to the topology of §9 on operations ∨ and ∧ are continuous on , and .
2.3. Examples of Directed Ringoids
13. Example. Ringoids and ordinals. The class of all ordinals has the addition and the multiplication operations which are generally non-commutative, associative, with unit elements 0 and 1 respectively, on the right distributivity is satisfied (see Propositions 4.29–4.31 and Examples 1–3 in [19,22]). Relative to the interval topology generated by the base the class is the topological well-ordered semiring, where . For each non-void set A in there exists (see [20]).
14. Example. Construction of ringoids with the help of inductive limits. Let J be a directed set of the cardinality such that for each there exists with and (see also §I.3 [21]), and let be a monotone decreasing map, , let also be an embedding for each . There is considered as a ringoid with the addition, the multiplication, with neutral elements by addition and by multiplication and the linear ordering inherited from for each . Put to be the inductive limit of the direct mapping system so that G is the quotient of the direct sum by the equivalence relation Ξ caused by mappings . Then consider , where , notates the projection.
Then we define and for all , where for each . Let also in G if and only if for each . Certainly for each there exists so that and , for example, for each . Therefore we get that if and in G, then and . We supply G with a topology inherited from the inductive limit topology on , where is supplied with the standard metric of and has the topology inherited from . Then we deduce that and for every and and with , where . Since for each , then the addition and the multiplication in G are continuous. Thus is the topological directed ringoid with the left and the right distributivity in which the multiplication is non-associative, since for each . It is worth to note that each set of the form is open in , where .
15. Example. The case of for each , where ω is a directed set, can be considered analogously to Example 14, taking the lexicographic ordering on the Cartesian product and considering M instead of J.
16. Example. On G from Example 14 one can take also and . Then is a topological non-associative ringoid with the left and right distributivity.
17. Example. Ringoids associated with families of measures. Let be a Boolean algebra on a set and let be an embedding for each with so that for each , where J and are as in subsection 14. Suppose that on each Boolean algebra there is a probability (finitely additive) measure so that is metrizable by the metric , where . Otherwise it is possible to consider the quotient algebra , where if and only if . Put and , where , , is the inductive limit of Boolean algebras, , denotes the projection.
Consider on G the inductive limit topology , where is supplied with the metric for each . Naturally it is possible to put in G if and only if for each . Then the inequalities
- and
Instead of measures it is possible more generally to consider submeasures , that is possessing the subadditivity property: for each satisfying the inclusion .
18. Example. Ringoids induced by spectra of non locally compact groups. Let be a family of topological non locally compact groups , where J is a directed set, is a continuous injective homomorphism for each in J. Let also be an increasing map and let be a Radon probability σ-additive measure on the Borel σ-algebra of such that is left quasi-invariant relative to for each with . That is there exists the Radon-Nikodym derivative (i.e., the left quasi-invariance factor) for each , where , , for each , where denotes a σ-algebra which is the completion of by -null sets.
It is assumed that a uniformity on is such that and is complete for each with . Suppose also that there exists an open base of neighborhoods of such that their closures in are compact.
It is known that such systems exist for loop groups and groups of diffeomorphisms and Banach-Lie groups.
Then for denotes the Banach space of all -measurable functions such that for each and
where for each and , with . Next we consider the space
for each
where
There exists the non-associative normed algebra supplied with the multiplication
such that
for every and , where , , (see [11,12,13,23]).
Now we take the positive cone
in and put
,
for each and define
in F if and only if for each and -almost all . Therefore, for every , and -almost all , where , since is the probability measure, and for -almost all and -almost all correspondingly. Thus for each .
If and , , then and
for -almost all and hence and . Then we infer that
for every and , where , , , is the projection, consequently, . Analogously it can be verified that for every .
For each there exists an element so that and , for example, either or u given by the formula for each and -almost all .
Take on F the topology inherited from the norm topology on . This implies that is the directed topological non-associative ringoid with the left and right distributivity.
There is the decomposition for each , where and , for each and .
If f and h in F are incomparable, there exist (may be either or ) such that and , where
- and
- . Then for
19. Note. Certainly relative to the discrete topology the aforementioned ringoids are also topological ringoids. Other examples can be constructed from these using the theorems and the propositions presented above.
3. Skew Morphisms of Ordered Semirings and Ringoids
3.1. Morphisms and Their Properties
1. Notation. Let denote the mapping on with values in such that
and for each and , where for each , whilst the sum is taken element-wise for every and .
2. Definition. We call a mapping ν on (or or ) with values in K an idempotent (K-valued) morphism if it satisfies for each (or in or correspondingly) the following five conditions
- (1)
- ;
- (2)
- and
- (3)
- ;
- (4)
- when satisfy Condition 2.12 and
- (5)
- if satisfy Condition 2.12,
A mapping (morphism) ν on (or or ) with values in K we call order preserving (non-decreasing), if
- (6)
- for each
A morphism ν will be called K-homogeneous on (or or ) if
- (7)
- and
- (8)
3. Remark. If a morphism satisfies Condition 2, then it is order preserving.
The evaluation at a point morphism defined by the formula:
- (1)
If morphisms are idempotent and the multiplication in K is distributive, then for each constants
- (2)
- in K with
- (3)
- morphisms
- (4)
- and
- (5)
The considered here theory is different from the usual real field , since has neither an infimum nor a supremum, i.e. it is not well-ordered and satisfy neither 2.3 nor 2.4.
4. Lemma. Suppose that either
K is well-ordered and satisfies Conditions 2.4 or
X is linearly ordered and K is directed and satisfies Conditions 2.3 and 2.4. Then there exists an idempotent K-homogeneous morphism ν on in case , on and in case . Moreover, if and K is infinite, X is not a singleton, , , then ν has not the form either 3 or 3 with the evaluation at a point morphisms relative to the standard addition in .
Proof. Suppose that ν is an order preserving morphism on (or or ). If in (or or respectively) satisfy Condition 2.12, then in accordance with Lemma 2.12 there exists and in the corresponding (or or ). Since and and and and the morphism ν is order preserving, then and .
Let also E be a subset in X, we put
- (3)
- .
From the fact that the addition preserves ordering on K (see §2.1) it follows that Properties are satisfied for the morphism ν given by Formula . If on X, then for each there exists so that , consequently, , i.e., 2 is fulfilled.
We consider any pair of functions in (or or ) satisfying Condition 8. In case a topological space X is linearly ordered, in case K is well-ordered, hence , , and are linearly ordered in K. Then for each there exist so that , while for each there exists so that , hence . Moreover, for each there exists so that and for each there exists so that , consequently, . Thus Properties 2 are satisfied as well.
If E is chosen such that there exists with , then this morphism ν is continuous on , and (see §§2.3, 2.4, 2.9 and 2.10 also).
If a set X is not a singleton, , and is infinite, , then taking a set E in X different from a singleton, , we get that the morphism given by Formula can not be presented with the help of evaluation at a point morphisms by Formula either 3 or 3 relative to the standard addition in , since functions f in (or or ) separate points in X (see Remark 2.5).
5. Remark. Relative to the idempotent addition the morphism given by 4 has the form .
Let denote the set of all idempotent K-valued morphisms, while denotes its subset of idempotent homogeneous morphisms.
A set F of all continuous K-valued morphisms on is supplied with the weak* topology having the base consisting of the sets
- ;
- ;
- ;
6. Definitions. A morphism is called weakly additive, if it satisfies Conditions 2;
normalized at , if Formula 2 is fulfilled;
non-expanding if when and when for any and ,
where ν may be non-linear or discontinuous as well.
The family of all order preserving weakly additive morphisms on a Hausdorff topological space X with values in K will be denoted by .
If satisfies the conditions: , and for each and , then E is called an A-subset.
7. Lemma. If is an order preserving weakly additive morphism, then it is non-expanding.
Proof. Suppose that and are such that or for each , then 2 imply that or respectively. Thus the morphism ν is non-expanding.
8. Corollary. Suppose that a topological ringoid K is well-ordered, satisfies 1 and with the interval topology, , is supplied with the topology of §2.9. Then any order preserving weakly additive morphism is continuous.
Proof. This follows from Lemma 7 and §§2.3, 2.4, since each subset and is closed in in the topology of §2.9, where .
9. Lemma. Suppose that A is an A-subset (a left or right submodule over K) in and is an order preserving weakly additive morphism (left or right K-homogeneous with left or right distributive ringoid K correspondingly). Then there exists an order preserving weakly additive morphism such that its restriction on A coincides with ν.
Proof. One can consider the set of all pairs so that B is an A-subset (a left or right submodule over K respectively), , μ is an order preserving weakly additive morphism on B the restriction of which on A coincides with ν. The set is partially ordered: if and is an extension of . In accordance with Zorn’s lemma a maximal element in exists.
If , there exists . Let and , then for each and , consequently, an element exists such that due to Conditions 2.3 and 2.4 imposed on K. Then we put ( is a minimal left or right module over K containing E and g correspondingly). Then one can put and . Moreover, one gets or for each correspondingly for each . Then μ is an order preserving weakly additive morphism (left or right homogeneous correspondingly) on F. This contradicts the maximality of A.
10. Theorem. If a ringoid K is well-ordered and satisfies 1, with the interval topology and K is locally compact, . Then is compact relative to the weak* topology.
Proof. In view of Lemma 8 each is continuous. The set is supplied with the weak* topology (see §5).
For each one has , since and . On the other hand, for each due to Condition 2.4 a supremum exists, . Each segment in K is closed, bounded and hence compact relative to the interval topology. Therefore, is contained in the Tychonoff product , since and hence when for each . This product is compact as the Tychonoff product of compact topological spaces by Theorem 3.2.13 [21]. It remains to prove, that is closed in S, since a closed subspace of a compact topological space is compact (see Theorem 3.1.2 [21]).
Each compact Hausdorff space has a uniformity compatible with its topology (see Theorems 3.19 and 8.1.20 [21]). To each element a morphism corresponds, since for each . If is a net converging to q in S, then Properties 2 for each imply Properties 2 for q, since each segment in K is compact and hence complete as the uniform space due to Theorem 8.3.15 [21], where . Therefore, according to Lemma 7 and Corollary 8. Thus is complete as the uniform space by Theorem 8.3.20 [21] and hence closed in S in accordance with Theorem 8.3.6 [21].
11. Proposition. In the topological space the subsets and are closed.
Proof. From the definitions above it follows that . If is a net in (or in ) converging to a morphism relative to the weak* topology (see also §1.6 [21]), then μ satisfies Conditions 2 (or to 2 respectively). Thus and are closed in .
12. Corollary. If the conditions of Theorem 10 are satisfied, then the topological spaces and are compact.
3.2. Categories of Semirings, Ringoids and Morphisms
13. Definition. If topological spaces X and Y are given and is a continuous mapping, then it induces the mapping according to the formula: for each and .
By will be denoted the restriction of onto .
A topological space will be called K-completely regular (or K Tychonoff space), if for each closed subset F in X and each point a continuous function exists such that and , i.e. h is constant on F, where .
Let denote a category such that a family of its objects consists of all K-regular topological spaces, a set of morphisms consists of all continuous mappings for every , i.e. is a subcategory in the category of topological spaces. We denote by a category with objects and families of morphisms .
14. Lemma. . There exists a covariant functor in the category . . Moreover, if a topological ringoid K is well-ordered, satisfies 2.4 and with the interval topology, when , , , , then is continuous.
Proof. . If and , in , then in , consequently, for each . If , , then , and for each . If , for each , then for each and for each . On the other hand, for each , i.e., . Evidently, .
. If is a net converging to ν in relative to the weak* topology, then for each and , since and are weakly* compact according to Theorem 10, consequently, is continuous from to .
15. Proposition. If for , then
.
Proof. If are such that or exists and is a continuous mapping, then
- or
- .
and
.
16. Definitions. A covariant functor will be called epimorphic (monomorphic) if it preserves epimorphisms (monomorphisms). If is an embedding, then will be identified with .
If for each and each closed subset A in Y, the equality is satisfied, then a covariant functor F is called preimage-preserving. When for each family of closed subsets in the monomorphic functor F is called intersection-preserving.
If a functor F preserves inverse mapping system limits, it is called continuous.
A functor F is said to be weight-preserving when for each , where denotes the topological weight of .
A functor is said to be semi-normal when it is continuous, monomorphic, epimorphic, preserves weights, intersections, preimages and the empty space.
If a functor is continuous, monomorphic, epimorphic, preserves weights, intersections and the empty space, then it is called weakly semi-normal.
17. Lemma. Let Y be a normal topological space, let also A and B be nonintersecting closed subsets in Y, where T is a well-ordered set supplied with the interval topology. Suppose also that are such that for each with an element exists such that (i.e. a segment is without gaps). Then a continuous function exists such that and .
Proof. Consider the segment in T. There exists a set E dense in such that
- (1)
- , , ,
- (2)
- , , .
We define open subsets in X such that
- (3)
- for each ,
- (4)
- , ,
Sets will be defined by the transfinite induction. For this one can put and . Therefore, , consequently, . In view of the Zermelo theorem there exists an ordinal P such that , a bijective surjective mapping exists such that , , and . Suppose that satisfying Condition are constructed for , . There exist elements and . Therefore, . From the normality of X it follows that open sets U and V exist such that , and , consequently, and hence . Then one puts . This means that there exists a countable infinite sequence for satisfying Conditions . If is not dense in the process continues. Suppose that α is an ordinal such that , is defined for each . If the set is not dense in , there exists a segment
such that . We put and . From it follows that the set L is open in X and . On the other hand,
for every such that and . If
is not contained in this segment is skipped, where is an interior of M in X. If one can put and . Then the process continues for .
The family is ordered by inclusion: if and only if a bijective monotonously increasing mapping exists such that for each . If a subfamily is linearly ordered, then its union is in . In view of the Kuratowski-Zorn lemma there exists a maximal element in for some ordinal such that conditions are satisfied.
Put for and when . Therefore, for each , and . Since is supplied with the interval topology it is sufficient to prove that and are open in for each and . From , also from when is fulfilled, and the definition of f it follows that and are open in .
18. Lemma. If X is well-ordered and E is a segment in X, while K satisfies Condition 2.3, then each has a continuous extension .
Proof. Since is linearly ordered in K, then by 2.3 there exists a well ordered subset B in K such that . So putting for each in X, whilst for each in X one gets the continuous extension of f, that is for each , since and exist in K due to 2.3 and 2.4.
19. Definition. It will be said that a pair of a topological space X and a ringoid K has property if for each closed subset E in X and each continuous function , i.e., or or , there exists a continuous extension , i.e., so that or or respectively.
Henceforward, it will be supposed that a pair has property .
20. Definitions. If Hausdorff topological spaces X and Y are given and is a continuous mapping, are ordered topological ringoids (or may be particularly semirings) with an order-preserving continuous algebraic homomorphism then it induces the mapping according to the formula:
for each and , where , , is defined on .
By will be denoted the restriction of onto . The shorter notations and are used when K is fixed, i.e. . When and we write simply and respectively omitting .
Let denote a category such that a family of its objects consists of all topological spaces, a family of morphisms consists of all continuous mappings for every .
Let be the category objects of which are all ordered topological ringoids satisfying Conditions 2.3 and 2.4, consists of all order-preserving continuous algebraic homomorphisms for each . Then by we denote its subcategory of well-ordered ringoids and their order-preserving algebraic continuous homomorphisms.
We denote by a category with the families of objects and morphisms for every and . Furthermore, stands for a category with families of objects and morphisms for every and .
By will be denoted a category objects of which are linearly ordered topological spaces, while consists of all monotone nondecreasing continuous mappings , that is for each , where . Then we put for each and , , according to the formula:
for each and and , where is defined on . Then the category with families of objects and morphisms and the category with and are defined.
Subcategories of left homogeneous continuous morphisms we denote by , , , correspondingly. These morphisms are taken on subcategories in or in of left distributive topological ringoids.
21. Lemma. There exist covariant functors , and , in the categories and respectively.
Proof. Suppose that and , while in , where (or in ) is marked, then in . Therefore one gets for each . Now if , , then , but also the equalities are fulfilled and for each . Then for , that is for each , one deduces for each and for each . On the other hand, for each , i.e. . But at the same time, the equalities are valid: , since the composition of continuous mappings is continuous.
Moreover, if , then . Furthermore, for the categories (or ) the proof is analogous with , and , where (or ) is marked.
22. Proposition. Suppose that for or in . Then
and for or or for or correspondingly.
Proof. If are such that or exists (see Condition in Lemma 2.12) and is a continuous mapping, (or ), then we infer that
- or
- .
and
.
Then for (or ) one gets .
23. Definitions. A covariant functor will be called epimorphic (monomorphic) if it preserves continuous epimorphisms (monomorphisms). If is a continuous embedding, then will be identified with .
If for each and each closed subset A in Y, the equality is satisfied, then a covariant functor F is called preimage-preserving. In the case for each family of closed subsets in (or in ), the monomorphic functor F is called intersection-preserving.
If a functor F preserves inverse mapping system limits, it is called continuous.
A functor is said to be semi-normal when it is monomorphic, epimorphic, also preserves intersections, preimages and the empty space.
If a functor is monomorphic, epimorphic, also preserves intersections and the empty space, then it is called weakly semi-normal.
24. Proposition. The functor (or , , ) is monomorphic.
Proof. Let (or in respectively) with a continuous embedding (order-preserving respectively). Then we suppose that (or in , , correspondingly). This means that a mapping (or in correspondingly) exists such that . A function (or in respectively) exists such that , hence . Thus (or , , correspondingly).
25. Corollary. The functors I, , and are monomorphic.
Proof. This follows from Proposition 24 and Definitions 20.
26. Proposition. The functors , , and are epimorphic, when (see §14 also).
Proof. Let be a continuous surjective mapping, (or in , , respectively). The set L of all continuous mappings with (or in correspondingly) is the A-subset according to Definitions 6 or the left module over K in (or in ). Then we put . This continuous morphism has an extension from L to a continuous morphism (or in , , correspondingly) due to Lemmas 9, 14 and Corollary 8.
27. Lemma. Let L be a submodule over K of or relative to the operations ∨, ∧, and containing all constant mappings , where . Let also be an idempotent (left homogeneous) continuous morphism. For each or there exists an idempotent (left homogeneous) continuous extension of ν on a minimal closed submodule M containing L and f.
Proof. For each we put
- (1)
- .
and
.
On the other hand for each one gets
.
From the inequalities for and it follows, that , consequently, . Then
.
But , since for and , consequently, . If ν is left homogeneous, then for each , consequently, ν is left homogeneous on M. If ν is continuous and is a net in M converging to (see §2.9), then
28. Lemma. If suppositions of Lemma 27 are satisfied, then there exists an idempotent (left homogeneous) continuous morphism λ on or respectively such that .
Proof. The family of all extensions of ν on closed submodules M of or respectively is partially ordered by inclusion: if and only if and . In view of the Kuratowski-Zorn lemma [20] there exists the maximal closed submodule P in or correspondingly and an idempotent extension of ν on P. If or correspondingly by Lemma 27 this morphism could be extended on a module L containing P and some or in respectively. This contradicts the maximality of . Thus or correspondingly.
29. Proposition. The functors I, and , are epimorphic.
Proof. Let a continuous mapping be epimorphic. We consider the set L of all continuous mappings such that or . Then L is a submodule of or relative to the operations ∨, ∧, and L contains all constant mappings , where . Then we put for or in , or . In view of Lemma 28 there is a continuous extension of μ from L onto or such that or in , or correspondingly.
30. Definition. It is said that (or ) is supported on a closed subset E in X, if for each or in such that . A support of ν is the intersection of all closed subsets in X on which ν is supported.
31. Proposition. Let or in . Then ν is supported on if and only if for each or in correspondingly such that . Moreover, E is a support of ν if and only if ν is supported on E and for each proper closed subset F in E, i.e. with , there are or in respectively with such that .
Proof. Consider such that for each functions with . A continuous morphism ν induces a continuous morphism such that for each with . Denote by the identity embedding of a closed subset E into X. Each function has an extension on X with values in K by Condition 19. Then , since and hence for each such that .
If and ν is supported on E, then by Definition 30 there exists a morphism such that . Therefore the equalities are valid: for each functions such that .
If E is a support of ν, then by the definition this implies that ν is supported on E. Suppose that , and for each with the equality is satisfied, then a support of ν is contained in F, hence E is not a support of ν. This is the contradiction, hence there are with such that .
If ν is supported on E and for each proper closed subset F in E there are with such that , then ν is not supported on any such proper closed subset F, consequently, each closed subset G in X on which ν is supported contains E, i.e. . Thus E is the support of ν.
32. Proposition. The functors , I, , , , preserve intersections of closed subsets.
Proof. If E is a closed subset in X, then there is the natural embedding (or , when ) due to Condition 19. Therefore, (or respectively). For any closed subsets E and F in X and each functions (or ) with there exists a function (or ) such that and due to 19. Therefore and for each (or in ). In view of Proposition 31 the functors and preserve intersections of closed subsets. This implies that the functors I, , and also have this property.
33. Proposition. Let be an inverse system of topological spaces , where V is a directed set, is a continuous mapping for each , is a continuous projection. Then the mappings
- (1)
- and
- (2)
- and
- (3)
- and
- (4)
- and
Proof. We consider the inverse system and its limit space . Then for each , since . Let denote the limit map of the inverse mapping system (see also §2.5 [21]).
A continuous morphism ν is in if and only if for each , since
if and only if and
, where , , for each , , for each , where is a thread of P such that , for each , is an order-preserving continuous algebraic embedding, is isomorphic with K.
If are two different continuous morphisms, then this means that a continuous function exists such that . This is equivalent to the following: there exists such that . Thus the mappings s and analogously t are surjective and bijective.
On the other hand,
and
for each and each and every such that either or or for each , also
and
for each and . Taking the inverse limit in Equalities gives the corresponding equalities for , where , hence t is the continuous algebraic homomorphism due to Theorem 2.5.8 [21].
Analogously s preserves Properties , that is is weakly additive, where for each . Suppose that , then for each due to . From for each , the inverse limit decomposition and Formula it follows that λ is order-preserving.
If for each , then a topological space X is linearly ordered: if and only if for each , where are threads of the inverse system P such that for each . Since is order-preserving for each and each is non-decreasing, then f is nondecreasing and hence for each , where and for each and , .
Moreover, is left homogeneous if and only if is left homogeneous for each , since . Applying Lemma 2.5.9 [21] one gets properties of mappings in Formulas .
34. Lemma. There exist covariant functors , , and , and , and , in the categories and and and respectively.
Proof. If , , , , then for each such that for each , where . That is . On the other hand, the equality is fulfilled.
If , then , where , . Therefore, if a mapping either or exists in , then or in respectively. If , then for each , particularly, this is valid for or , where . Therefore, and . To each and there corresponds a morphism on , (see §20). If is not an epimorphism, the image is a proper submodule over in .
If and , , then is a continuous homomorphism. If and (or and ) and or in , , then or in respectively.
This and the definitions above imply that , and , and , and , are the homomorphisms. Thus we deduce that and , and , , , and are the covariant functors on the categories , , and correspondingly with values in the categories of skew idempotent continuous morphisms, when a set or in correspondingly is marked.
35. Proposition. The bi-functors I on , on , on and on preserve pre-images.
Proof. In view of Proposition 24 and Lemma 34 I, , and are the covariant bi-functors, i.e., the functors in or and the functors in or or or correspondingly as well. For any functor F the inclusion is satisfied, where, for example, B is closed in .
Suppose the contrary that I does not preserve pre-images. This means that there exist and or and , , , and , where B is closed and hence A is closed when , such that but (or , and respectively). One can choose two functions such that
,
, and
.
There exist functions such that
and , while
and
and for each , where satisfy Conditions due to property 19. There are also functions such that
and with
and for each , where
, , such that and .
Evidently, and . Then
and
and .
On the other hand, there are functions , such that , , , and . Therefore, from Properties it follows that
and . The condition on A and on imply that
. Therefore,
and , which follows from . But Formulas contradict the inequality , since u is the order-preserving continuous algebraic homomorphism from into . Thus the bi-functors I and preserve pre-images. The proof in other cases is analogous.
36. Corollary. If or , , , where and or and , then or
correspondingly.
37. Definitions. Suppose that Q is a category and are two functors in Q. Suppose also that a transformation is defined for each , that is a continuous mapping is given. If for each mapping and every objects , then the transformation is called natural.
If is an endofunctor in a category Q and there are natural transformations the identity and the multiplication satisfying the relations and , then one says that the triple is a monad.
38. Theorem. There are monads in the categories , , and .
Proof. Let for and , where and . Therefore, this induces the morphism . Then
where for each , that is
- (1)
- and
Then we get . Moreover, we deduce that . Thus we get the equalities
and .
If additionally ν is left homogeneous and , then . Therefore, we infer that for every and .
For we put for each . Then , where denotes the constant mapping for each . From Formulas it follows that
On the other hand, from Formulas we get that
for each , . Thus .
If for some , then , hence . Analogously the mapping is defined for each and , also , for each and , for and , for and . One also puts or for , also or for correspondingly.
Next we verify that the transformations η and ξ are natural for each , i.e. , , :
where for each natural number m (see also §20 and Proposition 35).
For each and one gets
Let now and , then
where is prescribed by the formula for each . Thus is the monad. Since I is the restriction of the functor , the triple is the monad in the category as well. Analogously and form the monads in the category ; and are the monads in ; and are the monads in .
39. Proposition. If a sequence
- (1)
- in (or in ) is exact, then sequences
- (2)
- and
- (3)
- are exact (analogously for and correspondingly).
Proof. A sequence
is exact means that for each n, where is an order-preserving continuous algebraic homomorphism, . Each continuous homomorphism induces the continuous homomorphism point-wise for each . Therefore, we get that or , when or exists, where . Moreover, the equalities and are fulfilled, consequently, , since is zero if and only if for each . Thus the sequence
is exact.
Then a continuous morphism is zero on if and only if for each . Therefore, on if and only if for each . At the same time we have that , consequently, . Thus the sequences are exact, analogously for other functors , and .
3.3. Lattices Associated with Actions of Groupoids on Topological Spaces
40. Lemma. Let G be a topological groupoid with a unit acting on a topological space X such that to each element a continuous mapping corresponds having the properties
for each and
, where is the unit element, for each . If K is a topological ringoid with the associative sub-ringoid L, , such that
for each and , a continuous mapping satisfies the cocycle condition
and
for each and , then
is a representation of G by continuous in the variable mappings of into , when f is marked, where , for each and .
Proof. For each one has , hence . Moreover, , since and , i.e., is the unit operator on . Mappings are continuous in the variable as compositions and products of continuous mappings.
The continuous mappings are (may be) generally non-linear relative to K. If K is commutative, distributive and associative, then are K-linear on .
41. Definition. A continuous morphism ν on or we call semi-idempotent, if it satisfies the property:
for each or respectively, where for each .
Suppose that G is a topological groupoid with the unit continuously acting on a topological space X and satisfying Conditions 40. A continuous morphism λ on or we call -invariant if
, where for each and f in or correspondingly.
Let denote the family of all semi-idempotent continuous morphisms, when K is commutative and associative relative to the addition for , let also (or ) denote the family of all continuous morphisms satisfying Conditions 2 (or 2 correspondingly) for general K. Denote by (or or ) the family of all G-invariant semi-idempotent (or in or in correspondingly) continuous morphisms for , when as a topological space. We supply these families with the operations of the addition
in for and respectively and the multiplication being the convolution of continuous morphisms
in , where , .
Then we put , , , , and for the subsets of all left homogeneous morphisms in , , , , , correspondingly.
42. Proposition. If ν is a -invariant semi-idempotent continuous morphism, then its support is contained in , where
for a closed subset A in X. Moreover, if K has not divisors of zero a support of ν is G-invariant and contained in , where
Proof. If , then for each , when a continuous morphism ν is -invariant. On the other hand, if , then for each . At the same time, , since for each and . If , then , hence by induction we deduce that for each natural number n, where is the characteristic function of a set A, so that for each while for each .
If K has not divisors of zero, then for each element , hence , since and . That is is G-invariant. Since , then and by induction for each natural number n.
43. Proposition. If G is a topological groupoid with a unit or a topological monoid, then , and for general and K (or , and for or when K is commutative and associative relative to the multiplication) supplied with the convolution 41 as the multiplication operation are topological groupoids with a unit or monoids correspondingly.
Proof. Certainly, the definitions above imply the inclusion . If , then , when either for each or K is commutative and associative relative to the multiplication. We mention that the evaluation morphism at e belongs to and has the property for each , where e is a unit element in G, for each and . Thus is the neutral element in .
For a topological monoid G one has for each and so that is a function continuous in the variables s, u and x in G. Since ν and λ are continuous on , then is continuous on .
If G is a topological monoid, then for every and and , where means that a continuous morphism ν on a function h acts by the variable , consequently, . Thus the family is associative, when G is associative, where for the corresponding and K.
From §§2.3, 2.4, 2.9 and 5 it follows that the mapping is continuous.
44. Theorem. If G is a topological groupoid with a unit or a topological monoid, then (for K commutative and associative relative to +), and for general (or and for either or when K is commutative and associative relative to the multiplication) are topological ringoids or semirings correspondingly.
Proof. If or in and or exists (see Condition in Lemma 2.12), are continuous morphisms satisfying Condition either 2 or 2 respectively, then
- (1)
- (2)
- for each .
On the other hand, we deduce that
- and
- (3)
- and
- (4)
Therefore, Formulas and Proposition 43 imply that , , , and are left and right distributive topological ringoids or semirings correspondingly.
45. Theorem. If G is a topological groupoid with a unit, as a topological space (see §41), then is a closed ideal in , where (for K commutative and associative relative to +) or or or or with ; or for commutative and associative K relative to the multiplication with general .
Proof. We mention that , where the operation denoted by the addition is either + or ∨ or ∧ for or or correspondingly (and also below in this section), consequently, for each and , .
In Formula 41 after the action of a morphism λ on a continuous function in the variable x one gets that is a continuous function in the variable g and ν is acting on this function, i.e. , where . This implies that
- for ,
The property being G-invariant provides closed subsets in , since if a net of continuous mappings converges to a continuous mapping g an each is G-invariant, then is G-invariant as well.
If and , then
- and
- ,
- and
4. Conclusions
Skew continuous morphisms of ordered ringoids, semirings, algebroids and non-associative algebras can be used for studies of their structures and representations.
Conflicts of Interest
The author declares no conflict of interest.
References
- Baez, J.C. The octonions. Bull. Am. Mathem. Soc. 2002, 39, 145–205. [Google Scholar] [CrossRef]
- Birkhoff, G. Lattice Theory; Mathematical Society: Providence, RI, USA, 1967. [Google Scholar]
- Bourbaki, N. Algebra; Springer: Berlin, German, 1989. [Google Scholar]
- Dickson, L.E. The Collected Mathematical Papers. Chelsea Publishing Co.: New York, NY, USA, 1975; Volumes 1–5. [Google Scholar]
- Grätzer, G. General Lattice Theory; Akademie-Verlag: Berlin, German, 1978. [Google Scholar]
- Kasch, F. Moduln und Ringe; Teubner: Stuttgart, German, 1977. [Google Scholar]
- Kurosh, A.G. Lectures on General Algebra; Nauka: Moscow, Russian, 1973. [Google Scholar]
- Schafer, R.D. An Introduction to nonassociative Algebras; Academic Press: New York, NY, USA, 1966. [Google Scholar]
- Litvinov, G.L.; Maslov, V.P.; Shpiz, G.B. Idempotent functional analysis: an algebraic approach. Math. Notes 2001, 65, 696–729. [Google Scholar] [CrossRef]
- Ludkovsky, S.V. Topological transformation groups of manifolds over non-Archimedean fields, representations and quasi-invariant measures. J. Mathem. Sci. NY Springer 2008, 147, 6703–6846. [Google Scholar] [CrossRef]
- Ludkovsky, S.V. Topological transformation groups of manifolds over non-Archimedean fields, representations and quasi-invariant measures, II. J. Mathem. Sci., N. Springer 2008, 150, 2123–2223. [Google Scholar] [CrossRef]
- Ludkovsky, S.V. Operators on a non locally compact group algebra. Bull. Sci. Math. Paris Ser. 2 2013, 137, 557–573. [Google Scholar] [CrossRef]
- Ludkovsky, S.V. Meta-centralizers of non locally compact group algebras. Glasg. Mathem. J. 2015, 57, 349–364. [Google Scholar] [CrossRef]
- Weil, A. L’intégration Dans Les Groupes Topologiques et Ses Applications; Hermann: Paris, France, 1940. [Google Scholar]
- Bucur, I.; Deleanu, A. Introduction to the Theory of Categories and Functors; Wiley: London, UK, 1968. [Google Scholar]
- Fedorchuk, V.V. Covariant functors in the category of compacta, absolute retracts and Q-manifolds. Rissian Math. Surv. 1981, 36, 211–233. [Google Scholar] [CrossRef]
- Mitchell, B. Theory of Categories; Academic Press, Inc.: London, UK, 1965. [Google Scholar]
- Shchepin, E.V. Functors and uncountable powers of compacta. Russ. Math. Surv. 1981, 36, 1–71. [Google Scholar] [CrossRef]
- Mendelson, E. Introduction to Mathematical Logic; D. van Nostrand Co., Inc.: Princeton, NJ, USA, 1964. [Google Scholar]
- Kunen, K. Set Theory; North-Holland Publishing Co.: Amsterdam, Dutch, 1980. [Google Scholar]
- Engelking, R. General Topology; Heldermann: Berlin, German, 1989. [Google Scholar]
- Barwise, J. (Ed.) Handbook of Mathematical Logic; North-Holland Publishing Co.: Amsterdam, Dutch, 1977.
- Ludkovsky, S.V. Properties of quasi-invariant measures on topological groups and associated algebras. Ann. Math. Blaise Pascal 1999, 6, 33–45. [Google Scholar] [CrossRef]
© 2016 by the author; licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons by Attribution (CC-BY) license (http://creativecommons.org/licenses/by/4.0/).