Proposition 21.7.3.label Let $(X, \cm)$ be a measurable space, $E$ be a normed vector space over $K \in \RC$, and $\mathscr{M}\subset M(X, \cm; E)$ be a closed subspace such that:

  1. (P)

    For each $x \in X$, $\bracs{x}\in \cm$, and the delta mass $\delta_{x}$ is in $\mathscr{M}$.

Then, for any bounded measurable functions $\bracsn{f_n: X \to E^*|n \in \natp}$ and $f: X \to E^{*}$, the following are equivalent:

  1. (1)

    For each $\mu \in \mathscr{M}$, $\limv{n}\int f_{n} d\mu = \int f d\mu$.

  2. (2)

    For each $x \in X$, $\limv{n}f_{n}(x) = f(x)$, and $\sup_{n \in \natp}\norm{f_n}_{u} < \infty$.

Proof. (1) $\Rightarrow$ (2): By (P), for each $x \in X$, $\limv{n}f_{n}(x) = f(x)$. By the Uniform Boundedness Principle,

\[\sup_{n \in \natp}\norm{f_n}_{u} \le \sup_{n \in \natp}\norm{f_n}_{\mathscr{M}^*}< \infty\]

(2) $\Rightarrow$ (1): By the Dominated Convergence Theorem.$\square$

Post a Comment

Name:Email:
Please enter the tag of the current page (101) to post the comment.
Tag: