A Generalization of the Banach-Steinhaus Theorem for Finite Part Limits

It is well known, as follows from the Banach-Steinhaus theorem, that if a sequence $\left\{ y_{n}\right\} _{n=1}^{\infty}$ of linear continuous functionals in a Fr\'{e}chet space converges pointwise to a linear functional $Y,$ $Y\left( x\right) =\lim_{n\rightarrow\infty}\left\langle y_{n} ,x\right\rangle $ for all $x,$ then $Y$ is actually continuous. In this article we prove that in a Fr\'{e}chet space\ the continuity of $Y$ still holds if $Y$ is the \emph{finite part} of the limit of $\left\langle y_{n},x\right\rangle $ as $n\rightarrow\infty.$ We also show that the continuity of finite part limits holds for other classes of topological vector spaces, such as \textsl{LF}-spaces, \textsl{DFS}-spaces, and \textsl{DFS} $^{\ast}$-spaces,\ and give examples where it does not hold.

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