Fel's Conjecture for Numerical Semigroups #
A numerical semigroup: an additive submonoid of ℕ with finite complement.
The underlying set of natural numbers comprising the semigroup.
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The gap power sum G_r(S) = ∑_{g ∈ Δ} g^r (Definition 3 in the paper).
Equations
- S.gapPowerSum r = ∑ g ∈ S.gaps, ↑g ^ r
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The gap polynomial Φ_S(z) = ∑_{g ∈ Δ} z^g (Definition 4 in the paper).
Equations
- S.gapPolynomial = ∑ g ∈ S.gaps, Polynomial.X ^ g
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The Hilbert series H_S(z) = ∑_{s ∈ S} z^s, expressed as a formal power series.
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The coefficient of the Hilbert series at position n is 1 if n ∈ S.carrier, else 0.
The coefficient of the gap polynomial (viewed as a power series) at position n is 1 if n ∈ S.gaps, else 0.
For any n, we have n ∈ S.gaps ↔ n ∉ S.carrier.
The product of generators π_m = ∏ᵢ dᵢ (Definition 6 in the paper).
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The product polynomial P_S(z) = ∏ᵢ (1 - z^{dᵢ}) (Definition 6 in the paper).
Equations
- G.productPolynomial = ∏ i : Fin G.m, (1 - Polynomial.X ^ G.d i)
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Upper bound on the degree of the Hilbert numerator Q_S(z).
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- G.hilbertNumeratorDegBound = G.productPolynomial.natDegree + S.gaps.sup id + 1
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The Hilbert numerator Q_S(z), computed coefficient-wise from P_S and the gaps.
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- One or more equations did not get rendered due to their size.
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The coefficients cⱼ in the expansion Q_S(z) = 1 - ∑_{j ≥ 1} cⱼ z^j.
Equations
- G.numeratorCoeff j = if j = 0 then 0 else -G.hilbertNumerator.coeff j
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The alternating power sum C_n(S) = ∑_{j ≥ 1} cⱼ · jⁿ (Definition 8).
Equations
- G.alternatingPowerSum n = ∑ j ∈ Finset.range G.hilbertNumeratorDegBound, ↑(G.numeratorCoeff j) * ↑j ^ n
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The invariant K_p(S) = ((-1)^m · p!) / ((m+p)! · π_m) · C_{m+p}(S) (Definition 9 in the paper).
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The single factor `(e^{dᵢ t} -
- / (dᵢ t) = ∑_k dᵢ^k · t^k / (k+1)!
of theA` generating series.
Equations
- G.scaledExpFactor i = PowerSeries.mk fun (k : ℕ) => ↑(G.d i) ^ k / ↑(k + 1).factorial
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The generating series A(t) = ∏ᵢ (e^{dᵢ t} - 1) / (dᵢ t) (Definition 10).
Equations
- G.ASeries = ∏ i : Fin G.m, G.scaledExpFactor i
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The symbol T_n(σ) = n! · [t^n] A(t) (Definition 10).
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The generating series B(t) = (t / (e^t - 1)) · A(t) (Definition 11).
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The symbol T_n(δ) = (n! / 2^n) · [t^n] B(t) (Definition 11).
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Auxiliary series obtained by evaluating Q_S at t ↦ ∑ jⁿ t^n / n! per coordinate.
Equations
- One or more equations did not get rendered due to their size.
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Auxiliary helper: Q_S minus its constant term,
evaluated coefficient-wise on the exponential expansion.
Equations
- FelsConjectureProof.hilbertNumeratorExpSub G = PowerSeries.mk fun (n : ℕ) => (∑ j ∈ Finset.range G.hilbertNumeratorDegBound, ↑(G.hilbertNumerator.coeff j) * ↑j ^ n) / ↑n.factorial
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For a polynomial P : ℤ[X],
the formal power series ∑ₙ (P.coeff n : ℚ) · t^n / n! minus its constant term.
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- FelsConjectureProof.expPolySub P = PowerSeries.mk fun (n : ℕ) => (∑ j ∈ Finset.range (P.natDegree + 1), ↑(P.coeff j) * ↑j ^ n) / ↑n.factorial
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Generating function for the partial sums of P_S.coeff along Finset.range.
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- One or more equations did not get rendered due to their size.