Project outline: Intro to the Universal Property

This page is a placeholder for brainstorming about the outline for the Project proposal: Intro to the Universal Property. We want to make as complete a list as we can ahead of time of the pages that will be required for the project.

Scratch space for notes and possible pages / lenses

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Possible outline #1

(Copied from the proposal)

1. The idea of not caring about things except up to isomorphism.
2. The idea that we can describe objects based entirely on how they interact with other objects.
3. Introduce the category of finite sets, describing the empty set, disjoint union and product
4. Show how the empty set can be described entirely by its universal property.
5. Show how the union and product can be described entirely by their universal properties, up to isomorphism.
6. Introduce a specific poset category: $N$ with an arrow between $a$ and $b$ iff $a$ divides $b$. (Not sure about this one - maybe it already requires knowing what a category is?)
7. Describe the least upper bound and greatest lower bounds.
8. Describe the universal properties of the LUB and GLB; compare them with the union and coproduct.
9. Wrap up by explaining that this kind of property crops up all over the place.

Possible outline #2

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Core concepts that we should have at least a summary

• Universal_property
• Category theory
• Isomorphism