Transport of a link along a value functor #
The argument, stated once, behind the second clause of [Kol07, 34.1] (the value on a pull-back is
the pull-back of the value with the empty blow-ups deleted) for one link of a chain of Step 2 of
the proof of [Kol07, Theorem 103]: along a local analytic isomorphism h : N → M carrying an open
W' ⊆ N into W ⊆ M, a chain state over W' for the pulled-back triple and a chain state over
W whose sequences agree up to empty blow-ups after pulling back keep that relation through
one link (smaller opens V' ⊆ W', V ⊆ W with h(V') ⊆ V), whatever the value appended by the
link, as long as that value is read from a "value functor" with the two naturality properties: it
commutes with local analytic isomorphisms, and it does not see empty blow-ups. Here the value
functor is not fixed: the argument is stated for arbitrary appended values, the two naturality
properties entering as hypotheses on those values, and the three value functors of the
development are instances:
- the family of one boundary member at the induced triple (
ChainTransport.lean, the chain of Step 2.1); - the family functor of Step 2.2 at the triple of Step 2.2 (
Step2LinkTransport.lean, the link of Step 2.2); - an arbitrary family functor with the two naturality properties at the induced triple
(
Modified/InducedValueFunctor.lean, the rounds of the modified algorithm).
The argument, in two halves:
- The algebra of sequences (
BlowUpSequence.shrinkAppend_eraseEmpty_pullback): the shrink-and-append step ofL₂onNwith a valueF₂, with the empty blow-ups deleted and pulled back alongh|_{V'}, is the restricted sequence with the empty blow-ups deleted followed by the appended value transported to the common last stage (pullback_concat,eraseEmpty_concat,concat_map_stageOfEq,map_eq_pullback_symm), so the relation reduces to a comparison of the two appended values pulled back to that stage. - The comparison of the two appended values (
BlowUpSequence.valueTransport_rel): for valuesG₂on the reading open ofL₂,G₁on that ofL₁, given (i)G₂and the valueGPath^* L₁are the valuesGe₂,GePat the cleaned sequences transported alongeraseEmptyLast(the value functor ignores empty blow-ups;hA2,hA1), (ii)G₁pulled back along the restricted last-stage lift isGP(the value functor commutes with local isomorphisms;hFP), and (iii)Ge₂andGePagree under the identification of the cleaned sequences (a substitution alonghrel;hcongr, whose side conditionsmem_imageOpens_eraseEmptyLast_liftRange_iffandstageOfEq_eraseEmptyLast_liftCorestrict_applyare supplied), the two values pulled back to the common cleaned last stage agree. The maps are identified by the uniqueness of maps over the blow-down (eq_of_stageMap_last_comp_eq,LiftUnique.lean:liftCorestrict_pullbackLiftLast_comp_eq) and the opens bymem_liftRange_iff.
Over states of a chain (ChainState), the set-up of one link — the square of restrictions, the
identification of the two pull-backs of the sequence over W, the relation of the restricted
sequences, the triple over W' as a pull-back of the triple over W — is
ChainState.shrinkAppend_rel_of_value_rel and the lemmas before it: the relation is kept by the
shrink-and-append step as soon as the two appended values compare (hF).
The algebra of sequences #
The algebra of sequences of one link's transport: for sequences L₁ on M and L₂ on N
which agree, with the empty blow-ups deleted, after pulling L₁ back along hW : N → M, and for
the restrictions ρ : P → M, ρ' : Q → N, hV : Q → P forming a commuting square, the
shrink-and-append step of L₂ (with a value F₂ on its reading open), with the empty blow-ups
deleted, is the shrink-and-append step of L₁ (with F₁) pulled back along hV with the empty
blow-ups deleted, provided the two values agree after pulling back to the common last stage of the
restricted sequences with the empty blow-ups deleted (hF). e₀ identifies the two pull-backs of
L₁ to Q; hA the two restricted sequences.
stageMap_last_stageOfEq for the inverse isomorphism.
stageMap_last_eraseEmptyLast for the inverse isomorphism.
The last-stage lift of hW carries the reading open of ρ' on the pulled-back sequence into
the reading open of ρ on the sequence, when ρ ∘ hV = hW ∘ ρ'.
Membership in the image of an open under an analytic isomorphism.
The comparison of the two appended values #
The two image opens of the reading opens on the cleaned sequences correspond under the
identification stageOfEq hrel of the cleaned sequences (mem_liftRange_iff).
The blow-down of the common cleaned last stage through the pull-back of L₁ to Q (hA
followed by eraseEmptyLast).
The two transported maps into the cleaned reading opens agree under stageOfEq hrel: the
uniqueness of maps over the blow-down of the cleaned sequence (eq_of_stageMap_last_comp_eq).
The restricted map into the reading open of ρ factors through the last-stage lift of
hW: the uniqueness of maps over the blow-down of L₁ (eq_of_stageMap_last_comp_eq).
The transport of a link's value, the heart of the transport of a chain, for arbitrary
appended values: for sequences L₂ on N and L₁ on M whose restrictions agree, with the
empty blow-ups deleted, after pulling L₁ back along hW (hA), a value G₂ on the reading
open of ρ' on L₂ and a value G₁ on the reading open of ρ on L₁, both pulled back to the
common cleaned last stage of the restricted sequences and with the empty blow-ups deleted, agree,
provided
G₂and the valueGPon the reading open ofρ'onhW^* L₁are the valuesGe₂,GePon the cleaned sequences transported alongeraseEmptyLastand cleaned (the value functor ignores empty blow-ups;hA2,hA1);G₁pulled back along the restricted last-stage lift ofhWand cleaned isGP(the value functor commutes with local analytic isomorphisms;hFP);Ge₂andGeP, pulled back to the common cleaned stage, agree (hcongr; in the instances a substitution along the relationhrelof the cleaned sequences, the opens corresponding bymem_imageOpens_eraseEmptyLast_liftRange_iffand the maps bystageOfEq_eraseEmptyLast_liftCorestrict_apply).
The maps are identified by the uniqueness of maps over the blow-down
(liftCorestrict_pullbackLiftLast_comp_eq).
The set-up of one link over states of a chain #
The triple over W' is the pull-back of the triple over W along h|_{W'}.
The class of the triple over W, pulled back along h|_{W'}, from the class of the pulled-back
triple.
The order clause of a state over W' for the pulled-back triple, read at the triple over W
pulled back along h|_{W'}.
The square of restrictions: V ⊆ W after h|_{V'} is h|_{W'} after V' ⊆ W'.
The two pull-backs of the sequence over W to V' agree (e₀ of the transport).
The relation of the sequences over W' and W restricts to V' (hA of the transport).
The relation "the sequence over W' with the empty blow-ups deleted is the pull-back of the
sequence over W with the empty blow-ups deleted" is kept by the shrink-and-append step with
values F' over W' and F over W, for smaller opens V ⊆ W, V' ⊆ W' with h(V') ⊆ V, as
soon as the two values agree after pulling back to the common cleaned last stage of the
restricted sequences (hF, for the identifications pullback_restrictLE_pullback_restrictMap
and eraseEmpty_pullback_restrictLE). The algebra of sequences is
shrinkAppend_eraseEmpty_pullback.