Numerical action of the scalar-linear object twist #
The direct scalar-linear evaluation package now reaches the existing numerical
Seidel--Thomas formula without passing through additive EvaluationData.
LinearEvaluationData.IsEulerCopower identifies the evaluation term in the
generic cone subtraction formula with χ(E,X) • [E].
Exactness is automatic for every dg functor. Nothing here compares the additive and scalar-linear universal properties or asserts that the twist is an autoequivalence.
theorem
CategoryTheory.LinearEvaluationData.TwistConeData.twistK₀Of_eq_twistK₀
(k : Type w)
[Field k]
{C : Type u}
[DGCategory C]
[IsPretriangulated C]
[(X Y : C) → (p : ℤ) → Module k ↑((DGCategoryStruct.dgHom X Y).X p)]
[DGLinear k C]
[Triangulated.HomFiniteBounded k (H0 C)]
[∀ (n : ℤ), Functor.Linear k (shiftFunctor (H0 C) n)]
{E : C}
{V : LinearEvaluationData k E}
(K : TwistConeData k V)
(hV : IsEulerCopower k V)
(X : H0 C)
:
Triangulated.K₀.of (H0 C) (K.twist.h0.obj X) = (Triangulated.SphericalTwist.twistK₀ k (H0 C)
(have this := E;
this))
(Triangulated.K₀.of (H0 C) X)
Under the scalar-linear Euler copower formula, the evaluation cone has the
existing numerical twistK₀ class on every object.
theorem
CategoryTheory.LinearEvaluationData.TwistConeData.twistK₀Map_eq_twistK₀
(k : Type w)
[Field k]
{C : Type u}
[DGCategory C]
[IsPretriangulated C]
[(X Y : C) → (p : ℤ) → Module k ↑((DGCategoryStruct.dgHom X Y).X p)]
[DGLinear k C]
[Triangulated.HomFiniteBounded k (H0 C)]
[∀ (n : ℤ), Functor.Linear k (shiftFunctor (H0 C) n)]
{E : C}
{V : LinearEvaluationData k E}
(K : TwistConeData k V)
(hV : IsEulerCopower k V)
:
Triangulated.K₀.map K.twist.h0 = Triangulated.SphericalTwist.twistK₀ k (H0 C)
(have this := E;
this)
If scalar-linear evaluation realizes the Euler copower formula, its cone
induces the numerical twist endomorphism on K₀.