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@malarbol malarbol commented Oct 22, 2025

This PR introduces the notion of metric quotient of a pseudometric spaces: the metric space whose objects are quotient classes under the similarity relation in the pseudometric spaces and rational neighborhood relations given by neighborhoods of class-elements.

This is a metric space isometric to the original pseudometric space. In case of metric spaces, this isometry is an isometric equivalence. Any short map (resp. isometry) from a pseudometric space to a metric space factors as a short map (resp. isometry) through the metric quotient.

The module cauchy-approximations-metric-quotients-of-pseudometric-spaces introduces a few results regarding Cauchy approximations in pseudometric spaces and Cauchy approximations in their metric quotients.

Co-authored-by: Louis Wasserman [email protected]

malarbol and others added 18 commits October 21, 2025 22:40
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This is part (3/4) of my work towards #1458.

The last part is basically to take the metric quotient of the Cauchy pseudocompletion and work with that. It behaves like a Cauchy completion in a lot of ways but, as discussed in #1458, we can't prove that it is Cauchy complete.

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@fredrik-bakke fredrik-bakke left a comment

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This contribution is really well done, thank you for contributing it @malarbol. Sorry it took so long to review it

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Is the co-authorship tag on this PR correct? As far as I can see this work has been pretty independent?

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2 participants