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Nov 27 at 18:25 comment added Atom Okay, I will ask a new question if I hit a wall thinking about it. In any case, for all your time and responses, many thanks! :D
Nov 27 at 18:08 comment added Iosif Pinelis @Atom : Sorry, I do not engage in such chat. You may want to ask further questions about this answer right here. Actually, the question about the completion does not concern this answer directly. However, on the second thought, the Wikipedia claim is correct, and it follows by mentioned Theorem 1.36 in Rudin's book.
Nov 27 at 9:05 comment added Atom Let us continue this discussion in chat.
Nov 27 at 8:52 comment added Atom Ah, my bad! I meant $\sigma(\mathscr A\cup\{ \text{subsets of $m$-null sets of $\sigma(\mathscr A)$}\} )$ (which is the set $\{A\cup N : A\in\sigma(\mathscr A)\text{ and $N$ is a subset of an $m$-null set in $\sigma(\mathscr A)$}\}$).
Nov 27 at 3:27 history edited Iosif Pinelis CC BY-SA 4.0
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Nov 26 at 21:43 comment added Iosif Pinelis Previous comment continued: To see why the definition of the completion in my paper is equivalent to the one given in Theorem 1.36 in Rudin's book, you may want to use the last sentence in Proposition 2.3 in the paper.
Nov 26 at 21:10 comment added Iosif Pinelis Previous comment continued: (iii) Your "standard completion" is not in general a $\sigma$-algebra. Perhaps, here you meant the claim "In the above construction [...]" in section Construction of a complete measure, but that claim is of course false.
Nov 26 at 21:10 comment added Iosif Pinelis @Atom : Thank you for your appreciation of this answer. Some comments in response to yours: (i) The paper is published, with the content essentially identical to that of the preprint. (ii) The definition of the completion in the paper is standard. For instance, it is equivalent to the one given in Theorem 1.36 in Rudin's book.
Nov 26 at 19:22 comment added Atom In the preprint, you also compare the "completion" $\mathscr M_{\mathsf{Co}}$ of $\sigma(\mathscr A)$, defined by $\{E\subseteq X\colon \exists S\in\sigma(\mathscr A)\ d_X(E,S)=0\}$. However, this "completion" is in general larger than the standard completion, $\sigma(\mathscr A)\cup\{\text{subsets of $m$-null sets}\}$, correct?
Nov 26 at 19:04 comment added Atom What a complete answer! I am yet to read Proposition 1 above. I am going through your (very interesting!) preprint.
Nov 26 at 18:59 vote accept Atom
Nov 26 at 16:43 history edited Iosif Pinelis CC BY-SA 4.0
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Nov 26 at 14:54 history edited Iosif Pinelis CC BY-SA 4.0
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Nov 26 at 6:50 history answered Iosif Pinelis CC BY-SA 4.0