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Let $(E,\mathcal {A}, \mu ) $ be a finite measure space and $X$ be a Banach space. The set of all Bochner-integrable functions from $E$ into $X$ is denoted by $\mathcal{L}_X^1$.

If $X$ is reflexive, we have the following theorem

Theorem 1

Let $ (f_n)_{n\geq 1} \subset \mathcal {L}_{X}^1$ is a sequence with : $$\sup_n \int_{E}{\|f_n\| d\mu} < \infty .$$ Then there exist $ h _{\infty} \in \mathcal {L}_{\mathbb {R}}^1 $ and a sub-sequence $ (g_k)_k $ of $(f_n)_n $ such that for every sub-sequence $ (h_m)_m $ of $(g_k)_k$ : $$ \frac{1}{i}\sum_{j=1}^{i}{h_j(t)}\to h _{\infty}(t) \text{ weakly in }X\text{ a.e. }$$

Proof of this result exists in the article "Infinite-dimensional extension of a theorem of Komlos" by Erik J. Balder (Theorem A).

If $X$ is not reflexive, we have the following theorem

Theorem 2

Let $ (f_n)_{n\geq 1} \subset \mathcal {L}_{X}^1$ is a sequence with : $$ \begin{cases} \bullet~~ \{f_n(t)\}\text{ is relatively weakly compact a.e.,}\\ \bullet~~ \sup_n \int_{E}{\|f_n\| d\mu} < \infty.\\ \end{cases} $$ Then there exist $ h _{\infty} \in \mathcal {L}_{\mathbb {R}}^1 $ and a sub-sequence $ (g_k)_k $ of $(f_n)_n $ such that for every sub-sequence $ (h_m)_m $ of $(g_k)_k$ : $$ \frac{1}{i}\sum_{j=1}^{i}{h_j(t)}\to h _{\infty}(t) \text{ weakly in }X\text{ a.e. }$$

Proof of this result exists in the article "Infinite-dimensional extension of a theorem of Komlos" by Erik J. Balder (Theorem B).

My problem:

I want an example of a non-reflexive Banach space and two sequences, such that:

  • The first sequence is bounded in $\mathcal {L}_{X}^1$ but it does not verify the consequence of Theorem 1.

  • The second sequence verifying the hypotheses of Theorem 2 and its consequences.

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    $\begingroup$ The second point is easy: take $f_n \equiv 0$. $\endgroup$
    – gerw
    Commented May 13, 2020 at 6:07

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