This paper investigates the
relationships among tight, τ-additive, and σ-additive Baire measures on a
completely regular Hausdorff space X and its projective cover E(X). The most
interesting questions arise in the σ-additive case, and lead to the following
definitions: the space X has the weak (resp. strong) lifting property if for each
σ-additive measure on X, some (resp., every) pre-image measure on E(X)
is σ-additive. It is shown that every weak cb space has the strong lifting
property, while the Dieudonné plank fails even the weak lifting property.
Also, if X is weak cb, then X is measure-compact if and only if E(X) is
measure-compact.
Some applications to extensions of measures on lattices and to strict topologies on
spaces of continuous functions are given. A relationship between the lifting properties
mentioned above and conventional use of the term “lifting” in measure theory is
indicated.
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