Let (X,𝒜,μ) be a
measure space, and S ⊂ [1,∞). This paper investigates basic properties of
LP(S) = ⋂
t∈sLt(μ) and LI(S) = span of ⋃
t∈sLt(μ), when they are endowed with
appropriate projective and inductive topologies.
If X is μ-finite or μ is a counting measure, then LP(S), LI(S) are projective and
inductive limits in the usual sense. In this case the extensive abstract theory of
inductive and projective limits applies. In the general case, however, this theory does
not appear applicable. Using special properties of Lp-spaces a basic duality is
established between LP(S) and LI(S′), for the general case, where Sγ is the set of
conjugates to elements of S.
Next such properties as metrizability, normability and completeness for
LP(S),LI(S) are considered. The question of when LP(S) = LP(T) is also
considered, and it is shown that there is a certain maximal set T for which this is
true. Similarly for LI(S).
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