SilverSight/formal/CoreFormalism/EisensteinSeries.lean
allaun d2ece9d5ad feat: agent-produced extensions to SidonAdapter, UnitDistCandidateGen, and formal infrastructure
- SidonAdapter.lean: updated Singer construction integration
- UnitDistCandidateGen.lean: enhanced golden-angle perturbation
- WeightCandidateGen.lean: cmix weight matrix -> ManifoldShortcut
- ComplexProjectiveSpace.lean: Kaehler geometry scaffolding
- EisensteinSeries.lean: modular forms stub infrastructure
- test scripts: concurrency and Lean LLM integration tests
2026-07-04 01:05:14 -05:00

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/-
EisensteinSeries.lean — Modular Forms Stub Infrastructure
STATUS: SCAFFOLD — all theorems are HONESTY CLASS: CONJECTURE.
Full formalization requires the Mathlib modular forms module (T2.1 in
mathlib_missing_machinery.md). This stub provides the type signatures
and honest CONJECTURE axioms so the codebase compiles honestly while
waiting for Mathlib.
References:
Diamond-Shurman, "A First Course in Modular Forms", §4
Serre, "A Course in Arithmetic", Ch. VII
Koblitz, "Introduction to Elliptic Curves and Modular Forms", Ch. III
Mathlib already has:
- UpperHalfPlane (H := {z | im z > 0})
- ModularGroup SL(2,Z) action on H
- ArithmeticFunction.sigma (divisor sum) = σ_k(n) — PROVEN multiplicative
- EisensteinSeries/QExpansion.lean (partial — q-expansion coefficients)
What's MISSING (T2.1):
- M_k(SL(2,Z)) as finite-dimensional C-vector space
- Eisenstein series E_k for all even weights k ≥ 4
- Proof that M_* ≅ C[E_4, E_6]
- Rankin-Cohen brackets (for E_4^2 = E_8 identity)
- Hecke operators
-/
import Mathlib.NumberTheory.ArithmeticFunction
import Mathlib.NumberTheory.ModularForms.EisensteinSeries.QExpansion
namespace CoreFormalism.EisensteinSeries
open ArithmeticFunction
/-! ## §1 Divisor Sum Stubs
σ_k(n) = Σ_{d|n} d^k. Already available in Mathlib (ArithmeticFunction.sigma).
What's missing: the convolution identity that gives E_4^2 = E_8.
-/
/-- σ₃ convolution: Σ_{j=1}^{n-1} σ₃(j)·σ₃(n-j).
This is the self-convolution that appears in E_4^2 = E_8. -/
def sigma3_conv (n : Nat) : Nat :=
∑ j ∈ Finset.Icc 1 (n - 1), sigma 3 j * sigma 3 (n - j)
/-- HONESTY CLASS: CONJECTURE
The E_8 convolution identity:
σ₇(n) = σ₃(n) + 120·Σ_{j=1}^{n-1} σ₃(j)·σ₃(n-j)
Proven by computation for n ≤ 16 (E8Sidon.e8_conv_identity_16).
Proven for n ≤ 200 by tab extension (E8Sidon.e8_conv_identity_200, T1.1).
For all n: equivalent to E_4^2 = E_8 in the ring of modular forms.
BLOCKED ON: Mathlib modular forms module (T2.1/T3.1). -/
axiom e8_convolution_identity (n : Nat) :
sigma 7 n = sigma 3 n + 120 * sigma3_conv n
/-! ## §2 Eisenstein Series Type Stubs
E_k : H → C is a holomorphic modular form of weight k for SL(2,Z).
For even k ≥ 4, its Fourier expansion begins:
E_k(z) = 1 + (-1)^{k/2}·(2k/B_k)·Σ_{n≥1} σ_{k-1}(n)·q^n
where q = e^{2πiz}.
-/
/-- HONESTY CLASS: CONJECTURE
The Eisenstein series of weight k (k ≥ 4 even) as a function H → C.
Mathlib stub: only the type exists; the full definition needs T2.1. -/
opaque Eisenstein (k : Nat) : Type
/-- HONESTY CLASS: CONJECTURE
The q-expansion of E_k gives divisor sum coefficients:
E_k(z) = 1 + c_k·Σ_{n≥1} σ_{k-1}(n)·q^n
where c_k = -2k/B_k is a rational constant. -/
axiom eisenstein_fourier (k n : Nat) (hk : 4 ≤ k) (hk_even : Even k) :
True
-- Placeholder: the actual statement needs q-expansion API
/-- HONESTY CLASS: CONJECTURE
The weight-4 Eisenstein series squaring identity:
E_4^2 = E_8 in M_8(SL(2,Z)).
At the Fourier coefficient level, this yields the e8_convolution_identity.
This is the single most important missing theorem for the number theory
bridge between the E8 lattice and the Sidon set construction.
Expected to be proven once Mathlib has Rankin-Cohen brackets. -/
axiom e4_squared_equals_e8 : True
-- Placeholder: the actual statement needs modular forms ring API
end CoreFormalism.EisensteinSeries