2026-10-01
In our foundational work , we established the existence of multi-shell spherical cubatures on the Leech lattice through strength by reducing degree- harmonic moments under to modular forms in . In this companion paper, we develop the universal framework of Spectral Cone Duality governing strictly positive annihilation across discrete spectral systems, and deploy it to solve the fundamental structural, computational, and arithmetic questions arising from Part I.
First, we prove the Master Duality Theorem: across any finite-dimensional spectral evaluation system, the existence of strictly positive annihilators is strictly dual to the relative-interior enclosure of the origin (), or equivalently, the total triviality of non-negative dual states on the quotient space . In two dimensions, this is governed by the circular gap metric: is enclosed if and only if the maximal cyclic angular gap satisfies . We prove an Exact Rationality Lemma ensuring that every real positive solution admits an exact rational solution.
Second, in the geometry of the Leech lattice, we break the rigid contiguous window ansatz of via a pruned dictionary search, discovering point-minimized “slim” cubature designs: for Strength , skipping shell terminates the active support at rather than , achieving a point reduction and eliminating redundant points; for Strength , mid-window pair pruning eliminates points while retaining the minimal shell . We construct explicit rational dual Farkas certificates that rigorously certify the infeasibility of candidate shell supports. Analytically, we prove the Serre Vanishing Theorem: for , the maximal cusp vanishing order across is strictly , governed by the Serre obstruction , explaining the boundary shift observed in . We formulate the Modular Separation Conjecture, stating that the minimal contiguous radius is , verified up to weight .
Third, we analyze the microscopic sub-orbit structure of under the monomial frame group . We prove that Shell decomposes into three orbits whose normalized degree-4 harmonic moments balance with exact integer ratios . Exploiting this internal equilibrium, we construct exact compressed spherical -designs on sub-orbits of only points.
Finally, we apply spectral cone duality to rank-two and rank-three Hecke cusp spaces , determining the exact prime thresholds required to enclose the origin: , , , and . As an arithmetic consequence, every non-zero cusp form must exhibit a strict sign change within the prime evaluation window . We formalize the Finite Certification Problem, identifying the five functional-analytic stability requirements separating finite polyhedral certificates from unproven infinite-dimensional criteria.
A weighted spherical -design on the unit sphere is a finite point set with positive weights that integrates all polynomials of degree at most exactly against the normalized Haar measure : Equivalently, is a spherical -design if and only if for every homogeneous harmonic polynomial of degree , the weighted cubature moment vanishes:
In our foundational paper , we established the existence of exact rational spherical designs on the 24-dimensional Leech lattice through strength (degree ). By applying Reynolds group averaging over the automorphism group , all harmonic moments outside the invariant subspace vanish identically on every shell. By Venkov’s isomorphism theorem , the weighted theta series defines an isomorphism between and the cusp space vanishing to order at least two at infinity: Consequently, the infinite system of degree- harmonic cubature equations collapses to a finite rational system of scalar modular equations, which were audited via FLINT across contiguous shell windows up to .
While demonstrated the existence of rational solutions on contiguous shell windows, it left open several fundamental structural, geometric, and analytic questions:
Point Minimization: The contiguous shell windows used in suffer from combinatorial growth because the shell cardinalities grow asymptotically as . Can selective, non-consecutive shell pruning significantly reduce the total number of cubature points?
Analytic Boundary Mechanism: In , an empirical boundary shift was discovered for , but its analytic origin remained conjectural. Can this boundary shift be proved unconditionally?
Dual Infeasibility Certificates: When a candidate support fails to admit positive weights, can one provide an exact, finite certificate proving its impossibility, rather than relying on exhaustive search?
Sub-Orbit Mechanics: Can breaking the monolithic -shells into sub-orbits under subgroups like the monomial frame group yield compressed spherical designs with fewer points than individual shells?
Universal Spectral Geometry: What is the intrinsic convex geometry governing positive annihilation across discrete spectral systems? Can the same principles be applied to prime Hecke eigenbases?
In this paper, we resolve all five questions. We structure the paper into three interconnected parts:
Part A: Universal Spectral Cone Duality (Sections 2–3): The master relative-interior cone duality theorem, the exact rationality lemma, and the planar circular gap metric .
Part B: Discrete and Analytic Leech Lattice Geometry (Sections 4–6): Point-minimized slim designs, the Analytic Serre Vanishing Theorem, the Modular Separation Conjecture, explicit dual Farkas certificates, and sub-orbit 5-designs.
Part C: Hecke Prime Cones and the Infinite Frontier (Sections 7–8): Prime spectral enclosure thresholds for , deterministic cusp form sign changes, primal-dual complexity, and the five functional-analytic criteria governing infinite-dimensional limits.
Let be a finite-dimensional real vector space with dual space , and let be a finite collection of linear evaluation functionals. We define: The relative interior denotes the topological interior of the convex cone relative to its linear span .
Theorem 1 (Finite Spectral Cone Duality). Let be a finite-dimensional real vector space, let , and let and . The following three statements are equivalent:
Strict-Positive Annihilation: There exist weights such that:
Relative-Interior Enclosure: The origin belongs to the relative interior of the cone:
Dual Triviality on Quotient: The cone of vectors evaluating non-negatively on all of coincides with the annihilator :
Equivalently, on the quotient space , the non-negative dual cone is trivial: In particular, if spans (, so ), condition (iii) states that .
Proof. : Suppose with . For any generator , . Thus contains its own negation and is a linear subspace of . In any finite-dimensional linear subspace, the relative interior of the subspace is the subspace itself; hence .
: Suppose . Then is a linear subspace, forcing . Thus for each . By definition of , there exist coefficients such that . Summing over all gives: Setting , we have for each , yielding a strictly positive relation.
: Clearly . Conversely, let and let satisfy . Evaluating on gives . Since and for each , every term must vanish identically: for all . Hence , establishing .
: Define the evaluation map by . Condition (iii) asserts that the subspace intersects the non-negative orthant only at the origin: . By Gordan’s Theorem of the Alternative , there exists orthogonal to , which means in . ◻
Lemma 2 (Exact Rationality Lemma). Let . If , then .
Proof. Because has rational entries, Gaussian elimination produces a basis for consisting entirely of rational vectors. Consequently, the -linear span of this basis, , is dense in the real subspace in the Euclidean topology. Let . Since the positive orthant is open in , the intersection is open in the relative topology of and contains . By density, there exists a rational point in this neighborhood. In particular, and for every . ◻
Convex duality manifests in two distinct geometric modalities:
Remark 3 (Contrast with Gaussian Quadrature). In classical Gaussian quadrature on , the target functional is represented on polynomials by positive weights over nodes. Gaussian quadrature is not merely an instance of linear cone programming on a fixed node set: it optimizes the node positions via the roots of the -th orthogonal polynomial, using an infinite continuous dictionary . The dual witness certifying that nodes fail is the square polynomial , which satisfies . In modular cubatures, by contrast, the nodes are arithmetically fixed (shells or prime Hecke operators ) and the target functional is the origin .
Let be equipped with an auxiliary inner product , and let denote the unit sphere in . For any non-zero functional , denote its normalized vector by .
Proposition 4 (Hemispherical Separation Criterion). Let be a finite set spanning . Then: Equivalently, there exists no non-zero vector such that for all .
When , this condition reduces to a cyclic angular gap:
Definition 5 (Largest Circular Gap). Let be non-zero planar vectors with polar angles , sorted cyclically as . The largest circular gap is:
Proposition 6 (Planar Annihilation Criterion). Let be a finite set spanning . Then:
In , cubatures were constructed using contiguous shell windows . However, because shell cardinalities scale asymptotically as , the total point count: is overwhelmingly dominated by the terminal shell . Consequently, eliminating the highest shell by selectively pruning intermediate shells yields dramatic point-count reductions.
Theorem 7 (Point-Minimized Slim Designs for Strengths ). Exact rational positive spherical designs on exist on the following non-consecutive pruned shell dictionaries:
Strength 29 (, ): The contiguous window in skipped , terminating at with points. By retaining and omitting , we obtain: This terminates at , requiring points (), achieving a point reduction and eliminating points.
Strength 33 (, ): The contiguous window in discarded the minimal shell and required points. Omitting the pair yields: This restores the minimal shell , requires points, and saves points.
Strength 43 (, ): While the contiguous window used , omitting instead of yields , restoring and saving points.
To prove that a candidate shell dictionary cannot admit positive weights, it suffices by Theorem 1 to construct a single rational dual witness vector such that: For any hypothetical positive weight vector , , an immediate contradiction.
Proposition 8 (Explicit Dual Infeasibility Witness at ). For degree (), the contiguous window fails to admit positive weights. The unique dual vector solving is: Evaluating across yields: This certificate proves unconditionally that cannot support a positive cubature.
In , FLINT audits revealed that for , the minimal positive starting shell satisfies . We now prove that this boundary shift is an exact analytic theorem governed by Serre’s theorem.
Theorem 9 (Analytic Bound on Maximal Cusp Vanishing Order). Let be an even integer with . Then:
The maximal order of vanishing at the cusp across is strictly:
The subspace of forms achieving this maximal cusp vanishing order is one-dimensional:
Proof. Write with . By Venkov’s isomorphism (Theorem [thm:harmonic-isomorphism] in ), , where . Suppose a non-zero form were divisible by . The quotient form would be holomorphic on and at , transforming with modular weight: By Serre’s theorem, there are no non-trivial holomorphic modular forms of weight 2 for : Thus , forcing , a contradiction. Therefore, for all . Conversely, has because has a simple zero at the cusp and . Multiplying by yields . ◻
Theorem 9 proves that the first Fourier evaluations are linearly independent and span . However, positive cubatures additionally require enclosing the origin.
Conjecture 10 (The Modular Separation Conjecture). Let with dimension . The minimum integer such that the contiguous window admits a strictly positive annihilator is given unconditionally by:
This conjecture has been verified computationally through weight 122 across all modular branches.
In , Shell 8 was shown to split under into the doubled minimal orbit and primitive octad orbits, exhibiting a canonical harmonic sign inversion ( vs. ).
We now analyze the sub-orbit structure of the minimal shell under the monomial frame group .
Under , the vectors of decompose into three orbits:
Family A: Shape of cardinality .
Family B: Shape on Golay octads of cardinality .
Family C: Shape of cardinality .
Proposition 11 (Invariant Harmonics under ). Let . The space of -invariant harmonic polynomials satisfies: On the sphere (where is constant), the 1-dimensional space of degree- harmonic invariants is spanned by the curvature polynomial:
Proof. Central inversion eliminates all odd degrees. For , -invariance forces , and -transitivity forces , so . Since , no non-trivial harmonic invariant exists. For , 2-transitivity of restricts polynomial invariants to . Expressing , the condition in dimension yields: uniquely determining the harmonic ratio . ◻
Theorem 12 (Orbit Curvature Equilibrium and Compressed 5-Designs). Let denote the total integrated degree- harmonic moment of an orbit. Normalized by the common divisor , the orbit moments satisfy: The identity reflects the fact that uniform weights on form an 11-design. Furthermore, because for , any two-orbit combination satisfying forms an exact spherical -design on :
Compressed 5-Design on ( points): Assigning per-vector weights with ratio: yields an exact spherical -design on points.
Compressed 5-Design on ( points): Assigning per-vector weights with ratio: yields an exact spherical -design on points.
Let be the space of cusp forms of weight with Hecke eigenbasis . Under the unitary Deligne normalization: each prime defines a spectral evaluation vector .
Proposition 13 (Prime Enclosure and Dual Sign Alternation). Let be a finite set of primes such that spans .
The origin belongs to if and only if there exist weights such that .
If , then every non-zero cusp form must strictly change sign on :
We define the prime spectral enclosure threshold as the minimal prime such that .
| Space | Threshold | Required | Pre-Threshold Gap | Enclosing Metric | |
|---|---|---|---|---|---|
| 2 | 4 primes | ||||
| 2 | 5 primes | ||||
| 2 | 5 primes | ||||
| 3 | 8 primes | Contained in hemisphere | Hemisphere breached |
Proposition 14 (Certified Computational Verification for ). The enclosure thresholds and separating certificates for are certified as follows:
The Space (): The Hecke operator has exact characteristic polynomial with roots . The Deligne normalizer is . The evaluation vectors are (), (), (), and ().
Separation at : The vectors leave an open gap of . The rational dual vector strictly separates the cone from the origin:
Enclosure at : Since , the gap collapses to . The certified positive weights are:
The Space (): The Hecke operator has characteristic polynomial . For , the vectors leave an open gap of . At , lands at , reducing the gap to .
The Space (): The Hecke operator has characteristic polynomial . For , the gap is . At , lands at , closing the gap to .
The Space (): The Hecke operator has characteristic polynomial . For all primes (7 primes), the normalized vectors remain confined within an open hemisphere. At , breaches the separating hyperplane, establishing .
Definition 15 (Primal and Projective Dual Complexity). Let be an arithmetic spectral evaluation system with cost function .
The Primal Spectral Complexity is:
For a candidate support and an admissible reference functional , the Projective Dual Complexity is:
When strictly encloses the origin and spans , ; hence the feasible set for is empty and the dual complexity undergoes an infinite jump:
Let be an infinite-dimensional topological vector space with an exhaustive filtration (). The passage from finite polyhedral duality to global analytic positivity decomposes into three distinct regimes:
Regime I: Finite Existence (Per Truncation). On each finite-dimensional subspace , Theorem 1 holds unconditionally: either positive weights exist to represent or annihilate a functional, or an explicit dual witness separates the cone from the target.
Regime II: Effective Finite Bounds. Obtaining an explicit, computable bound such that the support can be restricted to . For modular forms, this is governed by the Sturm bound and the valence formula.
Regime III: Uniform Limiting Stability (The Analytic Frontier). Deducing an infinite-dimensional representation or positivity property ( for all ) from finite truncations.
Remark 16 (The Limits of Finite Cone Duality). We emphasize that: To pass rigorously from finite certificates to a global continuous certificate on , one must establish five independent functional-analytic stability requirements:
Uniform Boundedness: The total variation of the discrete measures must remain uniformly bounded: .
Topology of Convergence: The discrete sequence must converge in a specified weak- topology on .
Compatibility of Truncations: The finite systems must be asymptotically consistent with the filtration .
Closedness of the Dual Positivity Cone: The cone of non-negative test functions must be closed under the designated topology.
Normalization Control: The target functional must not degenerate under the limiting process.
We have developed the unified theory of Spectral Cone Duality, bridging convex geometry, discrete lattice designs, and arithmetic spectral systems. Building directly upon Part I , we have shown that non-consecutive pruned shell dictionaries achieve significant point-count compressions, that the boundary shift is an exact analytic theorem governed by , and that sub-orbits yield compressed spherical 5-designs on only points. Transposed to Hecke cusp spaces, spectral cone duality provides exact certificates of prime enclosure and deterministic cusp form sign alternation. Finally, we have formalized the functional-analytic requirements governing the transition to infinite-dimensional positivity. Audit file is available at:
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