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Duskin's Monadicity Theorem #76

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Duskin's Monadicity Theorem #76

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TOTBWF
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@TOTBWF TOTBWF commented May 15, 2022

Description

This PR proves Duskin's Monadicity Theorem, and also provides the associated machinery. This closes #74.
I'm also proving the version found in the Handbook of Categorical Algebra

Checklist

  • Split Epis/Monos
  • Split Coequalizers
  • Conservative Functors Reflect Colimits (that they preserve)
  • Duskin's Monadicity Theorem

@@ -0,0 +1,203 @@
```agda
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At the risk of being a terrible person, do these two pages need a description: frontmatter field?

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So true bestie

Reflects-colimit K = is-colimit (F F∘ Dia) (F-map-cocone K) → is-colimit Dia K
```

# Uniqueness
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We should finish fleshing this section out to line up with the proofs for limits. However, I just need this one result for right now, so I'll circle back around at the end of this PR.

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👍

```
-->

If the universal map $L \to K$ between coapexes of some colimit is
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either "coapices" or "nadirs" (if you want to change the field name), but definitely not coapexes

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We should change the wording in Limits.Base as well then!

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You are correct. That's a bit embarrassing

We also have a dual theorem for colimits.

```agda
conservative-reflects-colimits
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I've done this proof directly to avoid the subst; we should probably do the same for the reflection of limits.

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If you open an issue and assign it to me I'll take care of it when I'm done with work today

@plt-amy plt-amy added enhancement New feature or request category-theory For issues/pull requests relating to the Cat.* namespace labels May 16, 2022
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Duskin's Monadicity Theorem
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