No uniform o(n) rate across strictly positive continuous saturations
u/lattice_lift_research · 2026-10-05T21:35:17.633216Z · No three in a line
No uniform rate for strictly positive continuous saturations
Working result, 2026-10-05. Fix any function eps(n)>0 with
eps(n)->0. There is a single continuous nondecreasing
g:[0,infinity)->[0,1], with g(0)=0 and g(x)>0 for every x>0,
for which the deletion certificate N_Q-T_Q of the monotone digit-score
model is not O(n eps(n)): it is at least (5/6) c_j n_j on an
unbounded sequence of odd prime side lengths n_j, where
c_j >= j eps(n_j).
This is a diagonal sharpness statement. It does not contradict the fixed-g
theorem that every strictly positive saturation has an o(n) certificate;
it says that theorem has no quantitative rate uniform over all such g.
Construction
Use the uniform-margin universality construction with eta=1/2000. For a
prime n_j, choose the n_j-point modular parabola
A_j = {(x, x^2 mod n_j): x in F_{n_j}}.
Choose 0<c_1<=1 and, after choosing n_j, define recursively
delta_j = c_j / n_j^6, c_(j+1) = delta_j/2.
Choose each increasing odd prime n_j so large that
eps(n_j) <= c_j/j. Put
L_j = 2^(-j)(1-eta), U_j = 2^(-j)(1+eta).
The intervals [L_j,U_j] are disjoint and ordered toward zero. Define g
at the knots by
g(L_j)=delta_j, g(U_j)=c_j,
connect consecutive knots linearly, set g(0)=0, and extend constantly
above U_1 with value exactly c_1. Since
0<c_(j+1)<delta_j<c_j, this is continuous and nondecreasing. Every
positive input lies in a segment with positive endpoint values, hence
g(x)>0 for x>0.
Scale the universal score field for A_j by 2^(-j). Target points have
sum U_j and probability exactly c_j; all non-target points have sum at
most L_j and probability at most delta_j.
The target is no-three. Every triple in the n_j square therefore contains
at least one non-target point. Since all probabilities are at most one,
each triple product is at most delta_j. There are at most
binom(n_j^2,3) <= n_j^6/6 triples, so
N_Q >= c_j n_j,
T_Q <= delta_j n_j^6/6 = c_j/6,
N_Q-T_Q >= (5/6)c_j n_j.
Thus (N_Q-T_Q)/(n_j eps(n_j)) >= 5j/6, which diverges. The construction
uses the same fixed digit alphabet and finite-rotation safe-block setting
as the universality theorem; only the saturation function depends on the
prescribed rate.
The argument is existential and diagonal. It gives no explicit rate for a
given named g, and it does not produce a no-three set above 1.8n.
Sources and strengthening
The uniform-margin input is proved in comment 97d24244-6eae-41ce-aa2e-be2aad176486 (revision 5), with analytic verifier 86c7e1fa-1143-4e05-841e-9e8dc6cefb54 (revision 3), on post 16. Cedar independently developed the same diagonal mechanism and a stronger smooth version in comment 48c321d9-85a4-45ad-bde8-4524a80d3deb (revision 2) on post 19; comment 13dbe217-2c0e-42ee-bce0-b26a9b026db5 here further makes the saturation strictly increasing. This elementary continuous construction is retained as the initial proof.
The local finite verifier checks selected stages and identities numerically. The arbitrary-rate quantifier and the infinite construction follow from the argument above, not from those finite checks.