2 research outputs found

    Representation of HH-closed monoreflections in archimedean ellell-groups with weak unit

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    The category of the title is called mathcalWmathcal{W}. This has all free objects F(I)F(I) (II a set). For an object class mathcalAmathcal{A}, HmathcalAHmathcal{A} consists of all homomorphic images of mathcalAmathcal{A}-objects. This note continues the study of the HH-closed monoreflections (mathcalR,r)(mathcal{R}, r) (meaning HmathcalR=mathcalRHmathcal{R} = mathcal{R}), about which we show ({em inter alia}): AinmathcalAA in mathcal{A} if and  only if AA is a countably up-directed union from HrF(omega)H{rF(omega)}. The meaning of this is then analyzed for two important cases: the maximum essential monoreflection r=c3r = c^{3}, where c3F(omega)=C(RRomega)c^{3}F(omega) = C(RR^{omega}), and CinHc(RRomega)C in H{c(RR^{omega})} means C=C(T)C = C(T), for TT a closed subspace of RRomegaRR^{omega}; the epicomplete, and maximum, monoreflection, r=betar = beta, where betaF(omega)=B(RRomega)beta F(omega) = B(RR^{omega}), the Baire functions, and EinHB(RRomega)E in H{B(RR^{omega})} means EE is {em an} epicompletion (not ``the'') of such a C(T)C(T)

    The H-Closed Monoreflections, Implicit Operations, and Countable Composition, in Archimedean Lattice-Ordered Groups with Weak Unit

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    In the category of the title, called W, we completely describe the monoreflections R which are H-closed (closed under homomorphic image) by means of epimorphic extensions S of the free object on ω generators, F(ω), within the Baire functions on ℝω, B(ℝω) ; label the inclusion eS: F(ω) → S. Then (a) inj eS (the class of objects injective for eS) is such an R, with eS a reflection map iff S is closed under countable composition with itself (called ccc), (b) each such R is inj eS for a unique S with ccc, and (c) if S has ccc, then A∈inj eS iff A is closed under countable composition with S. We think of (c) as expressing: A is closed under the implicit operations of W represented by S (and these are of at most countable arity). In particular, the family of H-closed monoreflections is a set, whereas the family of all monoreflections is consistently a proper class. There is a categorical framework to the proofs, valid in any sufficiently complete category with free objects and epicomplete monoreflection β which is H-closed and of bounded arity; in W the β is of countable arity, and βF(ω) = B(ℝω). The paper continues our earlier work along similar lines
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