On Augmented Posets And (Z 1, Z 1 )-Complete Posets

Transcription

1 On Augmented Posets And (Z 1, Z 1 )-Complete Posets Mustafa Demirci Akdeniz University, Faculty of Sciences, Department of Mathematics, Antalya, Turkey, demirci@akdeniz.edu.tr July 11, 2011

2 1

3 1 2 Q-spaces and their category Q-SPC

4 1 2 Q-spaces and their category Q-SPC 3

5 Primary concept in their approach is augmented poset that is a triple U = ( U, JU, MU), consisting of a poset U, a subset JU of P (U) in which each member has the join in U and a subset MU of P (U) in which each member has the meet in U. Augmented posets together with structure preserving maps constitute a category P. A structure preserving map h : U V here means a monotone map h : U V with the properties (a) For all S JU, h (S) JV and h ( S) = h (S),

6 Primary concept in their approach is augmented poset that is a triple U = ( U, JU, MU), consisting of a poset U, a subset JU of P (U) in which each member has the join in U and a subset MU of P (U) in which each member has the meet in U. Augmented posets together with structure preserving maps constitute a category P. A structure preserving map h : U V here means a monotone map h : U V with the properties (a) For all S JU, h (S) JV and h ( S) = h (S), (b) For all R MU, h (R) MV and h ( R) = h (R).

7 The category of spaces, denoted by S, is another central concept in BB-approach. The objects of S (the so-called spaces) and its morphisms generalize the notions of topological spaces and continuous functions. A space is defined to be a quadruple W = ( W, D(W ), Σ(W ), (W )) fulfilling the properties (S1) W is a set,

8 The category of spaces, denoted by S, is another central concept in BB-approach. The objects of S (the so-called spaces) and its morphisms generalize the notions of topological spaces and continuous functions. A space is defined to be a quadruple W = ( W, D(W ), Σ(W ), (W )) fulfilling the properties (S1) W is a set, (S2) D(W ) is a subset of P ( W ),

9 The category of spaces, denoted by S, is another central concept in BB-approach. The objects of S (the so-called spaces) and its morphisms generalize the notions of topological spaces and continuous functions. A space is defined to be a quadruple W = ( W, D(W ), Σ(W ), (W )) fulfilling the properties (S1) W is a set, (S2) D(W ) is a subset of P ( W ), (S3) Σ(W ) consists of all U D(W ) for which U D(W ),

10 The category of spaces, denoted by S, is another central concept in BB-approach. The objects of S (the so-called spaces) and its morphisms generalize the notions of topological spaces and continuous functions. A space is defined to be a quadruple W = ( W, D(W ), Σ(W ), (W )) fulfilling the properties (S1) W is a set, (S2) D(W ) is a subset of P ( W ), (S3) Σ(W ) consists of all U D(W ) for which U D(W ), (S4) (W ) consists of all B D(W ) with B D(W ).

11 A morphism f : W 1 W 2 in S is a function f : W 1 W 2 satisfying the next properties

12 A morphism f : W 1 W 2 in S is a function f : W 1 W 2 satisfying the next properties (S5) (f ) (D(W 2 )) D(W 1 ),

13 A morphism f : W 1 W 2 in S is a function f : W 1 W 2 satisfying the next properties (S5) (f ) (D(W 2 )) D(W 1 ), (S6) (f ) (U) Σ(W 1 ) for all U Σ(W 2 ),

14 A morphism f : W 1 W 2 in S is a function f : W 1 W 2 satisfying the next properties (S5) (f ) (D(W 2 )) D(W 1 ), (S6) (f ) (U) Σ(W 1 ) for all U Σ(W 2 ), (S7) (f ) (B) (W 1 ) and for all B (W 2 ).

15 A morphism f : W 1 W 2 in S is a function f : W 1 W 2 satisfying the next properties (S5) (f ) (D(W 2 )) D(W 1 ), (S6) (f ) (U) Σ(W 1 ) for all U Σ(W 2 ), (S7) (f ) (B) (W 1 ) and for all B (W 2 ). Theorem [3] P is dually adjoint to S, i.e. there are functors Ψ :P op S and T :S P op such that T Ψ :P op S. Corollary [3] The full subcategory of P of all spatial objects ( SpaP) and the full subcategory of S of all sober objects ( SobS) are dually equivalent.

16 Q-spaces and their category Q-SPC Z-approach uses the notion of subset selection: A subset selection Z is a rule assigning to each poset P a subset Z (P) of its power set P (P). Subset selection Z V V P n F CN D BN elements of Z (P) no subset of P the empty set nonempty subsets of P with cardinality less than or equal to n finite subsets of P countable subsets of P directed subsets of P bounded subsets of P

17 Q-spaces and their category Q-SPC C C P A W nonempty linearly ordered subsets (chains) of P linearly ordered subsets (including ) of P subsets of P downsets of P well-ordered chains of P A subset selection Z is called a subset system [2, 6, 14] iff for each order-preserving function f : P Q, the implication M Z (P) f (M) Z (Q) holds. During this talk, Z will be assumed as a subset selection unless further assumptions are made.

18 Q-spaces and their category Q-SPC Definition [8, 18] A poset P with the property that each M Z (P) has the join (meet) in P is called a Z-join(meet)-complete poset. For simplicity, we call a Z 1 -join-complete and Z 2 -meet-complete poset a (Z 1, Z 2 )-complete poset. There are two useful subset selections Z sup 1 and Z2 inf derived from given two original subset selections Z 1 and Z 2 by the formulas Z sup 1 (P) = Z inf 2 (P) = { M Z 1 (P) } M exists in P, { N Z 2 (P) } N exists in P, With the help of these derived subset selections, every poset can be introduced as a ( Z sup 1, Z2 inf ) -complete poset.

19 Q-spaces and their category Q-SPC Definition A monotone map f : P Q is (Z 1, Z 2 )-continuous iff the following two conditions are satisfied: (i) For each M Z sup 1 (P), f ( M) = f (M), (ii) For each N Z inf 2 (P), f ( N) = f (N). Under the assumption Z 3 and Z 4 are subset systems, (Z 1, Z 2 )-complete posets and (Z 3, Z 4 )-continuous maps constitute a category Q-CPos, where Q stands for (Z 1, Z 2, Z 3, Z 4 ). Q-CPos provides a practically useful categorical framework for many order-theoretic structures.

20 Q-spaces and their category Q-SPC Example (Examples of Q-CPos) (F, V, V, V)-CPos=Category of join-semilattices with and monotone maps (SEMI [12]), (D, V, D, V)-CPos=Category of directed-complete posets and Scott-continuous functions (DCPO [1]), (P, P, C, V)-CPos=Category of complete lattices and maps preserving joins of chains (LC [13]), (P, P, V, V)-CPos=Category of complete lattices and monotone maps (LI [13]).

21 Q-spaces and their category Q-SPC Q-spaces and their category Q-SPC Z-approach suggests another generalization of topological space called Q-space: A Q-space is, by definition, a pair (X, τ) consisting of a set X and a subset τ (so-called a Q-system on X ) of P (X ) such that the inclusion map i τ : (τ, ) (P (X ), ) is a Q-CPos-morphism.

22 Q-spaces and their category Q-SPC Example (Examples of Q-systems) (V, V, V, V)-system=System [7, 8],, (P, F, P, F)-system=Topology [7, 8], (F, P, F, P)-system=Topological closure system [7, 8], (V, P, V, P)-system=Closure system [7, 8], (D, P, D, P)-system=Algebraic closure system [7, 8], (D, F, D, F)-system=Pretopology [11], (D, F, P, F)-system τ=pretopology τ such that for each V τ, if V is not directed but has the join in (τ, ), then V τ, (P, P, C, V)-system τ=(τ, ) is a complete lattice such that joins of chains are exactly unions of chains.

23 Q-spaces and their category Q-SPC Continuous functions turn into Q-space-continuous functions in Z-approach: A map f : (X, τ) (Y, ν) between Q-spaces (X, τ) and (Y, ν) is Q-space-continuous if the usual requirement of continuity (i.e. (f ) (ν) τ) is satisfied. Q-spaces and Q-space-continuous maps form a category Q-SPC extending the familiar category of topological spaces (Top) to the Z-approach.

24 We describe this relation via the functors G Q : Q-CPos P and H Q : Q-SPC S, defined by G Q (P) = H Q (X, τ) = ( ) P, Z sup 3 (P), Z4 inf (P), G Q (f ) = f, ( ) X, τ, Z sup 3 (τ), Z4 inf (τ) and H Q (g) = g It is easy to check that G Q and H Q are full embeddings, and so BB-approach is more general than Z-approach. Using these full embeddings, we may formulate spatiality and sobriety in Z-approach as follows: Definition (i) A (Z 1, Z 2 )-complete poset P is Q-spatial iff G Q (P) is spatial, (ii) A Q-space (X, τ) is Q-sober iff H Q (X, τ) is sober.

25 Theorem (Main result) Assume that Z 1, Z 2 are iso-invariant subset selections and Z 3, Z 4 are subset systems. Let Q-CPos s and Q-SPC s denote the full subcategory of Q-CPos of all Q-spatial objects and the full subcategory of Q-SPC of all Q-sober objects. (i) Q-CPos s and Q-SPC are dually adjoint to each other. (ii) Q-CPos s is dually equivalent to Q-SPC s. (iii) If Z 1 and Z 2 are surjectivity-preserving subset systems, then (Z 1, Z 2, Z 1, Z 2 )-CPos is dually adjoint to (Z 1, Z 2, Z 1, Z 2 )-SPC.

26 A subset selection Z is iso-invariant [6] iff for each order-isomorphism f : P Q, the implication M Z (P) f (M) Z (Q) holds A subset system Z is surjectivity-preserving iff for each surjective monotone map f : P Q and for each M Z (Q), there exists at least one N Z (P) such that f (N) = M.

27 Thank you for attending...

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