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removed some unnecessary space
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emilyriehl committed Oct 22, 2023
1 parent e64cd9a commit 00ef47e
Showing 1 changed file with 60 additions and 56 deletions.
116 changes: 60 additions & 56 deletions src/simplicial-hott/13-limits.rzk.md
Original file line number Diff line number Diff line change
Expand Up @@ -82,15 +82,17 @@ definitions coincide. Define cone as a family.
( b x : B )
( k : hom B b x)
: ( family-cone A B f x) → ( family-cone A B f b)
:= \ α → vertical-comp-nat-trans
( A)
( \ a → B)
( \ a → is-segal-B)
( constant A B b)
( constant A B x)
( f)
( constant-nat-trans A B b x k)
( α)
:=
\ α
→ vertical-comp-nat-trans
( A)
( \ _ → B)
( \ _ → is-segal-B)
( constant A B b)
( constant A B x)
( f)
( constant-nat-trans A B b x k)
( α)
```

Another definition of limit.
Expand All @@ -102,9 +104,9 @@ Another definition of limit.
( f : A → B)
: U
:= Σ (b : B),
Σ ( c : family-cone A B f b)
, ( x : B) → ( k : hom B b x)
→ is-equiv
Σ ( c : family-cone A B f b)
, ( x : B) → ( k : hom B b x)
→ is-equiv
( family-cone A B f x)
( family-cone A B f b)
( cone-precomposition A B is-segal-B f b x k)
Expand All @@ -126,15 +128,17 @@ definitions coincide. Define cocone as a family.
( x b : B)
( k : hom B x b)
: ( family-cocone A B f x) → ( family-cocone A B f b)
:= \ α → vertical-comp-nat-trans
( A)
( \ a → B)
( \ a → is-segal-B)
( f)
( constant A B x)
( constant A B b)
( α)
( constant-nat-trans A B x b k )
:=
\ α
→ vertical-comp-nat-trans
( A)
( \ _ → B)
( \ _ → is-segal-B)
( f)
( constant A B x)
( constant A B b)
( α)
( constant-nat-trans A B x b k )
```

Another definition of colimit.
Expand All @@ -146,12 +150,12 @@ Another definition of colimit.
( f : A → B)
: U
:= Σ (b : B),
Σ ( c : family-cocone A B f b)
, ( x : B) → ( k : hom B x b)
→ is-equiv
( family-cocone A B f x)
( family-cocone A B f b)
( cocone-postcomposition A B is-segal-B f x b k)
Σ ( c : family-cocone A B f b)
, ( x : B) → ( k : hom B x b)
→ is-equiv
( family-cocone A B f x)
( family-cocone A B f b)
( cocone-postcomposition A B is-segal-B f x b k)
```

The following alternative definition does not require a Segalness condition.
Expand Down Expand Up @@ -245,18 +249,18 @@ The type of cocones of a function with codomain a Segal type is a Segal type.
: is-covariant B ( \ b → family-cocone A B f b)
:=
is-covariant-substitution-is-covariant
( A → B)
( B)
( hom ( A → B) f)
( is-covariant-representable-is-segal
( A → B)
( is-segal-function-type
( funext)
( A)
( \ _ → B)
( \ _ → is-segal-B))
( f))
( \ b → constant A B b)
( A → B)
( B)
( hom ( A → B) f)
( is-covariant-representable-is-segal
( A → B)
( is-segal-function-type
( funext)
( A)
( \ _ → B)
( \ _ → is-segal-B))
( f))
( \ b → constant A B b)
#def is-segal-cocone-is-segal uses (funext)
( A B : U)
Expand All @@ -265,15 +269,15 @@ The type of cocones of a function with codomain a Segal type is a Segal type.
: is-segal ( cocone A B f)
:=
is-segal-total-type-covariant-family-is-segal-base
( naiveextext)
( naiveextext)
( B)
( family-cocone A B f)
( is-covariant-family-cone-is-segal
( A)
( B)
( family-cocone A B f)
( is-covariant-family-cone-is-segal
( A)
( B)
( is-segal-B)
( f))
( is-segal-B)
( f))
( is-segal-B)
```

Colimits are unique up to isomorphism.
Expand All @@ -285,16 +289,16 @@ Colimits are unique up to isomorphism.
( f : A → B)
( x y : colimit A B f)
: Iso
( cocone A B f)
( is-segal-cocone-is-segal A B is-segal-B f)
( first x)
( first y)
( cocone A B f)
( is-segal-cocone-is-segal A B is-segal-B f)
( first x)
( first y)
:=
iso-initial
( cocone A B f)
( is-segal-cocone-is-segal A B is-segal-B f)
( first x)
( first y)
( second x)
( second y)
( cocone A B f)
( is-segal-cocone-is-segal A B is-segal-B f)
( first x)
( first y)
( second x)
( second y)
```

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