The trace inequality at conductor 163 does not extend uniformly across the class-number-one Heegner-prime family

Paper XI in the singular Hecke node series
Richard Hoekstra · 2026

The question

Paper I proved |G(d,d')| ≤ 2 min(G(d,d), G(d',d')) for the Heegner operator set at level 163. Does this inequality hold across the entire class-number-one Heegner-prime family H' = {11, 19, 43, 67, 163}?

The nested gate sets

Let H = {2, 3, 7, 11, 19, 43, 67, 163} be the class-number-one Heegner primes. At each level N in H', the gate set is SN = {p in H \ {2} : p ≤ N}, with TN = UN = −wN at the prime level:

Level NGate set SNdim S₂(Γ₀(N))
11{3, 7, 11}1
19{3, 7, 11, 19}1
43{3, 7, 11, 19, 43}3
67{3, 7, 11, 19, 43, 67}5
163{3, 7, 11, 19, 43, 67, 163}13

The Gram matrices

N = 19, S₁₉ = {3, 7, 11, 19} — the 4 x 4 trace Gram matrix G₁₉(d, d') = Tr(TdTd' | S₂(Γ₀(19))):

371119
342−6−2
721−3−1
11−6−393
19−2−131

Violation: |G₁₉(7, 11)| = 3, but 2 min(G₁₉(7,7), G₁₉(11,11)) = 2 min(1, 9) = 2. Ratio: 3/2.

N = 67, S₆₇ = {3, 7, 11, 19, 43, 67} — the 6 x 6 Gram matrix:

3711194367
314−414−26−102
7−430−60−120
1114−628−5414−2
19−260−541352−5
43−10−12142134−14
6720−2−5−145

Violation: |G₆₇(43, 67)| = 14, but 2 min(G₆₇(43,43), G₆₇(67,67)) = 2 min(134, 5) = 10. Ratio: 14/10 = 7/5.

The answer

Negative result The inequality |GN(d, d')| ≤ 2 min(GN(d,d), GN(d', d')) holds at N in {11, 43, 163} and fails at N in {19, 67}.
Level NPairs testedStatusViolating pairViolation ratio
113Holds----
196Fails(7, 11) and (11, 19)3/2
4310Holds----
6715Fails(43, 67)7/5
16321Holds----

The dimension-one reduction

At N in {11, 19}, the cuspidal space is one-dimensional, so GN has rank one and factors as GN(d, d') = ad(fN) · ad'(fN). In this case the inequality reduces to:

maxp in SN |ap(fN)| ≤ 2 minp in SN |ap(fN)|

For N = 11 (11a1): (a₃, a₇, a₁₁) = (−1, −2, 1), absolute values (1, 2, 1), ratio 2 — holds at the boundary. For N = 19 (19a1): (a₃, a₇, a₁₁, a₁₉) = (−2, −1, 3, 1), absolute values (2, 1, 3, 1), ratio 3 > 2 — fails.

Conclusion: The trace inequality at conductor 163 is not a Heegner-family phenomenon. It holds at three of five levels and fails at the other two. The holding set {11, 43, 163} has cuspidal dimensions (1, 3, 13); the failing set {19, 67} has dimensions (1, 5). The worst violation ratio is 7/5 at N = 67.
This is an honest negative result. The inequality found in Paper I does not generalise, which tells us that the structure at level 163 is more special than the Heegner property alone can explain.
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