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DerivedAlgGeo.CategoryTheory.Triangulated.StabilityCondition.Mukai.Assembly

Assemble the Mukai stability function on the HN-tilted heart #

This file is the terminal categorical assembly for Bridgeland's four tilted-heart positivity cases. It consumes the two named geometric contracts from Mukai.GeometricInput and proves positivity for torsion generators, shifted torsion-free generators, and their extensions. The ambient exponential Mukai charge is consequently a StabilityFunction on the HN-tilted heart.

The parent constructor tiltStabilityFunctionOfPred takes the boundary contract for an arbitrary predicate P on the factors together with a proof that P forces positive real charge on a positive-rank factor at the cutoff. No Hodge-index hypothesis reaches it. tiltStabilityFunctionOfMargin chooses the exact Hodge margin as P; tiltStabilityFunctionOfLowerBound chooses a uniform lower bound realForm ≥ -δ and needs only 2δ < ω²; and tiltStabilityFunction is the legacy K3-normalized child δ = 1. Thus the categorical layer does not decide whether the geometric bound comes from the K3 stable-simple Ext calculation, a stronger abelian surface result, or another surface realization. None of these constructors chooses between ch and ch * sqrt(td); that choice has already been made by the additive Mukai class map m.

No Harder--Narasimhan property for the resulting stability function is claimed. The HN hypothesis below belongs only to the weak slope function used to define the torsion pair and its tilt.

The complete torsion-generator case, with only the residual rank-and-degree-zero classification supplied geometrically.

The complete shifted torsion-free generator case for a boundary decomposition into factors satisfying a predicate P, given that P forces positive real charge on a positive-rank factor at the cutoff. Strictly below the cutoff is formal slope arithmetic; equality is discharged by the decomposition contract. No Hodge-index hypothesis appears: whatever justifies hP stays with the consumer that chose P.

The exponential Mukai charge is positive on every nonzero object of the HN-tilted heart, for any boundary predicate whose real positivity has been proved. The generic HRS assembly reduces this to the two Mukai generator theorems.

The exponential Mukai charge as a stability function on the tilted heart, for any boundary predicate whose real positivity has been proved. This is the parent constructor: every other constructor in this file chooses P and supplies hP. It does not assert an HN property for the new stability function.

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    The complete shifted torsion-free generator case under the exact factorwise Hodge margin: tiltStabilityFunctionOfPred's predicate is the margin and re_charge_pos_of_margin is the positivity proof.

    The complete shifted torsion-free generator case for an arbitrary factorwise quadratic lower bound: the predicate is realForm ≥ -δ and re_charge_pos_of_lower_bound supplies positivity from 2δ < ω².

    The K3-normalized shifted-free theorem, obtained from the general lower bound with δ = 1.

    The exponential Mukai charge is positive on every nonzero object of the HN-tilted heart under the exact factorwise Hodge margin.

    The exponential Mukai charge is positive on every nonzero object of the HN-tilted heart under an arbitrary factorwise lower bound.

    The K3-normalized whole-heart positivity theorem, recovered at δ = 1.

    The exponential Mukai charge as a stability function on the tilted heart under the exact factorwise Hodge margin. The predicate is the margin of each factor; re_charge_pos_of_margin is the only Hodge-index input.

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      The exponential Mukai charge as a stability function on the tilted heart, parameterized by a factorwise quadratic lower bound. This is the categorical conclusion of the four-case positivity argument; it does not assert an HN property for this new stability function.

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        The historical K3-normalized stability-function constructor.

        This is the δ = 1 specialization of tiltStabilityFunctionOfLowerBound. The wrapper keeps existing consumers source-compatible while making the geometric constant explicit for new surface children.

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          @[simp]
          theorem CategoryTheory.Triangulated.MukaiWeakSlopeCompat.tiltStabilityFunctionOfLowerBound_Z {C : Type u_1} [Category.{u_3, u_1} C] [Preadditive C] [Limits.HasZeroObject C] [HasShift C ℤ] [∀ (n : ℤ), (shiftFunctor C n).Additive] [Pretriangulated C] [IsTriangulated C] {V : Type u_2} [AddCommGroup V] [Module ℝ V] {t : TStructure C} [FiniteDimensional ℝ V] (δ : ℝ) {m : K₀ C →+ Mukai.RealExtension V} {b : V →ₗ[ℝ] V →ₗ[ℝ] ℝ} {β ω : V} (hb : ∀ (x y : V), (b x) y = (b y) x) (hsigPos : sigPos (LinearMap.BilinMap.toQuadraticMap b) = 1) (hω : 0 < (b ω) ω) (hωδ : 2 * δ < (b ω) ω) {S : WeakSlopeData t.heart.FullSubcategory} (Cpt : MukaiWeakSlopeCompat (MukaiChargeData.ofAmbient t m) S b ω) (hHN : S.toWeakStabilityFunction.HasHNProperty) (hzero : MukaiTilt.HasDimensionZeroTorsionClasses m b β ω S) (hboundary : MukaiTilt.HasBoundaryMukaiDecompositionWithLowerBound m b β ω S δ) :
          (tiltStabilityFunctionOfLowerBound δ hb hsigPos hω hωδ Cpt hHN hzero hboundary).Z = MukaiChargeData.ambientChargeHom m b β ω