The K-level Tate pairing #
The first consumer of the base-generalized B6 (GQ2.tateDualityAt): the π½β-valued Tate
pairing on M = HΒΉ(G_K, π½β) for K the splitting field
(G_K = ker Ο), supplying the pairing hypotheses of the abstract hduality
(GQ2.card_equivHoms_deep_eq_quot, GQ2/DeepDuality.lean Β§F):
ker_isLocalDualizingGroupββ₯(ker Ο)is a local dualizing group (the subtype embedding; finite index fromFinite C), sotateDualityAtapplies:tateDualityK.pairingK := inv_K β cuponHΒΉ(β₯(ker Ο), π½β), through the coefficient bridgeZMod 2 β+ MuDual 2 (ZMod 2)(zmodMuDualEquiv) and the(1,1)evaluation cup.- (H2)
pairingK_nondegβ nondegeneracy, from the bundle'sperfect11injectivity. - (H1)
pairingK_conjActβ conjugation invarianceB(gΒ·x, gΒ·y) = B(x, y): the cup cocycle precomposes on the nose withconjMap Γ conjMap(the coefficient action is trivial), a coboundary transported alongconjMapstays a coboundary, andZMod 2-valued functions agreeing in vanishing agree β noHΒ²-action needs to be constructed (HΒ²(G_K, ΞΌβ) β β€/2has trivial automorphisms, so invariance is forced).
Everything is Ο.ker-vocabulary (no IntermediateField enters); the isotropy (H3) discharge
(cup_deepClasses lives over k.fixingSubgroup) is the f8 splice's k-plumbing.
Design details are recorded in docs/orchestration/p15f-handoff.md Β§8 and
docs/orchestration/p15f7-axiom-proposal.md.
G_K = ker Ο is a local dualizing group: the subtype topological embedding into
G_ββ has finite index (the quotient injects into the finite C) and acts on
ΞΌβ by restriction (definitionally).
The Tate-duality bundle at G_K β the first consumer of the base-generalized B6.
Equations
- GQ2.tateDualityK Ο = GQ2.tateDualityAt (β₯Ο.ker) 2 β―
Instances For
The kernel acts trivially on ΞΌβ (restriction of the trivial G_ββ-action).
The coefficient bridge π½β β+ Hom(π½β, ΞΌβ): a β¦ (m β¦ ΞΌβ-lift of aΒ·m). Feeds
H1congr to move HΒΉ(G_K, π½β)-classes into the duality bundle's MuDual-slot.
Equations
- One or more equations did not get rendered due to their size.
Instances For
Equivariance of the coefficient bridge (both sides carry trivial β₯(ker Ο)-actions:
π½β definitionally, the ΞΌβ-dual by smul_muN_two_trivial_ker).
The K-level Tate pairing on M = HΒΉ(G_K, π½β): transport the left argument through the
coefficient bridge, cup with the evaluation pairing, and read off through the invariant map of
tateDualityK β B(x, y) := inv_K (xβ² βͺ y).
Equations
- One or more equations did not get rendered due to their size.
Instances For
(H2) Nondegeneracy of the K-level pairing β the (1,1)-perfectness clause of the
base-generalized B6 at G_K: a class pairing trivially with everything is zero.
conjMap is multiplicative in the kernel argument.
conjMap Ο g inverts conjMap Ο gβ»ΒΉ.
Coboundary transport along conjugation: precomposition with conjMap Γ conjMap carries
BΒ²(ker Ο, ΞΌβ) into itself (Ξ΄ΒΉΟ β¦ Ξ΄ΒΉ(Ο β conjMap); the coefficient action is trivial).
The two-sided form: precomposition with conjMap Γ conjMap preserves BΒ² in both
directions.
conjAct on an H1mk-class: the mk-level form of conjAct_h1ofFun.
The invariant map kills conjugation: if the cocycle Fc is (pointwise) F precomposed
with conjMap Γ conjMap, the two inv-values agree. ZMod 2-valued, so it suffices that the
two classes vanish together β and vanishing is BΒ²-membership, transported by
comp_conjMap_mem_B2_iff. (Stated with the composition as an equation hypothesis so the
call site avoids higher-order unification.)
(H1) Conjugation invariance of the K-level pairing: B(gΒ·x, gΒ·y) = B(x, y) for the
conjAct-action of any g : G_ββ. The transported cup cocycle is on the nose the original
precomposed with conjMap Γ conjMap (the coefficient actions are trivial), and the invariant
map kills that precomposition (inv_H2mk_comp_conjMap).
(H1) in conjModule form β the literal hBinv hypothesis of the abstract hduality
(card_equivHoms_deep_eq_quot with instA := conjModule Ο hΟsurj).
The (H3) isotropy splice: pairingK vanishes on deep Γ deep #
Eq. (94)'s (U_{e+1}, U_{e+1}) = 1 in class vocabulary. The Tier-5 fact
(LocalKummer.cup_deepClasses, over the finite base k with the π½β-valued
trivialCupPairing) splices to pairingK on HΒΉ(ker Ο, π½β) across two boundaries:
- the group view
ker Ο = G_k, taken POINTWISE (hker : x β ker Ο β x β k.fixingSubgroup) so that no subgroup-equality cast is ever formed β the cup cocycles on the two sides are literally the same functions of the underlying group elements, and thek-side coboundary witnessΟtransports by precomposition with the identity inclusionkerToFixing; - the coefficient bridge
π½β β+ ΞΌβ(muNTwoEquiv.symm), which carries the transported witness's coboundary identity over pointwise (map_sub/map_add; all actions trivial).
Since inv_K is injective, vanishing of the HΒ²(ΞΌβ)-class (= BΒ²-membership of the explicit
cup cocycle) forces pairingK = 0. No new leaf: the axioms are tateDualityAt (B6β²) plus
cup_deepClasses's Tier-5 chain.
The identity inclusion β₯(ker Ο) β β₯(k.fixingSubgroup) under a pointwise identification
of the kernel with the fixing subgroup (G_K = ker Ο).
Equations
- GQ2.kerToFixing Ο k hker n = β¨βn, β―β©
Instances For
kerToFixing is multiplicative (both sides are the ambient product).
kerToFixing is continuous (it is the identity on underlying elements).
Norm bridge for MID units, the β€-mirror of LocalKummer.norm_sub_one_lt_of_isDeepUnit:
A = 1 + 2b with βbβ β€ 1 gives βA β 1β β€ β2β.
Bridge midClasses β kummerClassK β the β€-mirror of
LocalKummer.deepClass_eq_kummerClassK: over a finite base k, a mid Kummer class in
HΒΉ(G_k, π½β) is the Kummer class of a genuine U_e-unit a β kΛ£ (βa β 1β β€ β2β).
Eq. (94), mid β deep in class vocabulary over the finite base k
((U_e, U_{e+1}) = 1) β combines the two kummerClassK bridges with the Tier-5
cup_mid_deep.
(H3) Isotropy of the deep classes under the K-level pairing: two deep Kummer classes
pair to zero. Spliced from the Tier-5 cup_deepClasses as described in the section header.
Mid β deep under the K-level pairing β (U_e, U_{e+1}) = 1 spliced to ker Ο
(same witness-transport as pairingK_deep_deep, with the Tier-5 input
cup_midClasses_deepClasses). The "easy half" of (H4)'s sharpness Deep^β₯ = E.
The "easy half" of (H4) in pairPerp form: E = midClasses β€ Deep^β₯ under
pairingK. Sharpness (Deep^β₯ β€ E) follows from this + the cardinality balance
#Deep^β₯ = #(M β§Έ Deep) = #E (the counting brick).
The hiso input of the abstract hduality in pairPerp form:
Deep β€ Deep^β₯ under pairingK.