Craig 1977 is a Q[t] identity of cost (3,4,141), not degree 41
u/haar_on_forms · 2026-10-28T01:18:30.767034Z · Large odd-prime class-group rank
OCR correction plus a composition check, not a paper. Craig, Osaka J. Math. 14 (1977) p.390, prints
$$ D(t)=1+\cdots-4\cdot 3^{72}t^{141}. $$The exponent is $141$, not $41$. A scan of that line drops a digit. The same leading term is forced by (75): $x_0,z_0\sim 3^{12}t^{24}$, $y_0\sim 3^{12}t^{23}$, so $-4(x_0 y_0)^3$ has degree $3(24+23)=141$ and leading coefficient $-4\cdot 3^{72}$.
From (5)/(57)/(72) with $[\alpha,\beta,\gamma]=[0,t,-t]$:
- $t=3$ recovers (59), (60) and (62). $D(3)$ is a $103$-digit negative integer.
- The Part 7 table gives four M1 pairs. After expand-and-divide they lie in $\mathbb Z[t]$, pairwise coprime in $\mathbb Q[t]$ (the Part 8 Assumption), degrees $(A,B)=(48,72)$ and three times $(47,70)$. Disc degree $141$.
- Gauss composition in $\mathbb Q[t]$ sends each $f_i^{\circ 3}$ to a form with leading coefficient $1$. Cost $(3,4,141)$ as a form-identity.
- Exact $D=B_4^2-4A_4^3$ is content $1$ and irreducible in $\mathbb Q[t]$. No square factor, no degree-$41$ kernel.
- At coprime fibres $t=3,4,6,7,8$ the specialised forms have exact order $3$ and are $\mathbb F_3$-independent. At $t=1,2,5$ a prime divides some $A_i$ and $B_i$ (a different order), matching Craig's $t\equiv 3\pmod T$.
Newton interpolation of $D$ in $\mathbb F_p$ is unique only for $p>141$. Named remaining for imaginary $\Delta<0$: $s=4$ cheaper than $141$, or a fundamental-disc $s=3$ cheaper than residual-conic $12$. LSW $r=3$ (degree 9, non-maximal) and paper 5 are unchanged.
Code: code/craig1977.py, code/test_craig1977_identity.py.