A first-order functor on the projective corner trivializes the deformation #
integral-deformations.tex (proof of Lemma 10.2): "If its value is zero, arrow changes
remove all first-order mesh errors. The Hom category of the lifted modules becomes constant.
Restricting to its actual projective corner trivializes the algebra deformation."
Ring-generic form. Modules N_X over an R-algebra Λ carry first-order lifts of their
actions for a cocycle μ; the arrows φ_a and their corrections g_a satisfy the mesh
relations exactly and to first order. At projective labels p the module is regular,
N_p ≅ e_pΛ with generator w_p and inverse ψ_p, its lifted action is the regular one, and
evaluation at w_p identifies RQ(p, s) modulo the mesh ideal with N_p e_s. Then μ is a
Hochschild coboundary (eq_hcobdry), through the derivation Δ(b) = ∑_p ψ_p Δ_p(w_p b) with
Δ_p(n) = ∑_s δ(n e_s)(w_s).
The hypotheses of the projective corner argument.
- e_idem (p : P) : e p * e p = e p
- e_sum : ∑ p : P, e p = 1
- mesh (x : ↑Q.nonprojective) : ∑ a : (y : V) × (y ⟶ ↑x), ↑(u x a.fst a.snd) • φ a.snd ∘ₗ φ ((Q.mate x a.fst) a.snd) = 0
- zmesh (x : ↑Q.nonprojective) : ∑ a : (y : V) × (y ⟶ ↑x), ↑(u x a.fst a.snd) • (φ a.snd ∘ₗ g ((Q.mate x a.fst) a.snd) + g a.snd ∘ₗ φ ((Q.mate x a.fst) a.snd)) = 0
- w_e (p : P) : ((MM (lab p)).act (w p)) (e p) = w p
- surj (s p : P) (n : N (lab p)) : ((MM (lab p)).act n) (e s) = n → ∃ (F : LinearPaths.obj (lab s) ⟶ LinearPaths.obj (lab p)), ((PathEval.evL N fun {y x : V} => φ) F) (w s) = n
- inj (s p : P) (F : LinearPaths.obj (lab s) ⟶ LinearPaths.obj (lab p)) : ((PathEval.evL N fun {y x : V} => φ) F) (w s) = 0 → F ∈ (CategoricalIdeal.HomIdeal.linearSpan R (meshRelations u)).hom (LinearPaths.obj (lab s)) (LinearPaths.obj (lab p))
Instances For
The derivation on the regular modules #
A preimage of n e_s in RQ(s, p).
Instances For
Δ_p(n) = ∑_s δ(n e_s)(w_s).
Instances For
δF is the commutator of Δ with F.
The derivation on Λ #
The derivation on Λ: Δ(b) = ∑_p ψ_p(Δ_p(w_p b)).
Instances For
The component e_p x e_r of x as a morphism r → p.
Instances For
The derivation identity, the hypothesis of GExt.eq_hcobdry_of_derivation.
The trivialization: μ is a Hochschild coboundary.