Pervasiveness of $\mathcal{L}^r(E,F)$ in $\mathcal{L}^r(E,F^δ)$
Let $E, F$ be Archimedean Riesz spaces, and let $F^δ$ denote an order completion of $F$. In this note, we provide necessary conditions under which the space of regular operators $\mathcal{L}^r(E, F)$ is pervasive in $\mathcal{L}^r(E, F^δ)$. Pervasiveness of $\mathcal{L}^r(E, F)$ in $\mathcal{L}^r(E, F^δ)$ implies that the Riesz completion of $ \mathcal{L}^r(E, F)$ can be realized as a Riesz subspace of $ \mathcal{L}^r(E, F^δ$. It also ensures that the regular part of the space of order continuous operators $\mathcal{L}^{oc}(E, F)$ forms a band of $\mathcal{L}^r(E, F)$. Furthermore, the positive part $T^+$ of any operator $T \in \mathcal{L}^r(E, F)$, provided it exists, is given by the Riesz-Kantorovich formula. The results apply in particular to cases where $E = \ell_0^{\infty}$, $E = c$, or $F$ is atomic, and they provide solutions to some problems posed in [3] and [16].