I'm wondering if anyone has shown Fatou's lemma for sums when the limits are taken over nets. That is, has anyone proved the following? > If $\{x_{k,\alpha}\}_{k\in \mathbb N,\alpha \in \mathcal A}$ with > $\mathcal A$ a directed set, and $x_{k,\alpha}\geq 0$ for each $\alpha$ and $k\in \mathbb N$, then > > $$\sum_{k=1}^{\infty} \sup_{\bar \alpha}\inf_{\alpha\geq \bar \alpha} x_{k,\alpha}\leq \sup_{\bar \alpha}\inf_{\alpha\geq \bar \alpha} \sum_{k=1}^{\infty} x_{k,\alpha}.$$ This result is not true if the sum were replaced by a general measure.