Homotopy Type Theory monic function > history (Rev #7, changes)

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Definition

Given a natural number n:n:\mathbb{N} and types AA and BB, a function f:ABf:A \to B is a nn-monic function if for all terms b:Bb:B the fiber of ff over bb has an homotopy level of nn.

isMonic(n,f) b:BhasHLevel(n,fiber(f,b))isMonic(n, f) \coloneqq \prod_{b:B} hasHLevel(n, fiber(f, b))

A equivalence is a 00-monic function. 11-monic functions are typically just called monic functions or inclusions.

The type of all nn-monic functions with domain AA and codomain BB is defined as

monic(n,A,B): f:ABisMonic(n,f)monic(n, A, B): \sum_{f:A \to B} isMonic(n, f)

For Given every types natural number n A: n:\mathbb{N} A , andmonic(n,A,B) monic(n, B A, B) , has a homotopy level of n A n A . is called asubtype of BB, and BB is called a supertype of AA, if monic(1,A,B)monic(1, A, B) is inhabited. We define the proposition of subtype inclusion as

In particular, the type of all monic functions with domain AA and codomain BB, defined as

AB[monic(1,A,B)]A \subseteq B \coloneqq \left[monic(1, A, B)\right]
ABmonic(1,A,B)A \subseteq B \coloneqq monic(1, A, B)

where [T]\left[T\right] is the propositional truncation of TT. If AA and BB are sets, then AA is a subset of BB and BB is a superset of AA.

is The a type of all subtypes ofpropositionBB . in a universe is defined asAA is called a subtype of BB, and BB is called a supertype of AA. If AA and BB are sets, then AA is a subset of BB and BB is a superset of AA.

Sub 𝒰(B) A:𝒰𝒯 𝒰(A)BSub_\mathcal{U}(B) \coloneqq \sum_{A:\mathcal{U}} \mathcal{T}_\mathcal{U}(A) \subseteq B

See also

Revision on April 21, 2022 at 17:07:57 by Anonymous?. See the history of this page for a list of all contributions to it.