The lag that never survives
Worth reading first: The organ that was taken away · Counting the spirals.
When a cut wrecks a stem, the organs above the hole settle into an arrangement whose displacements repeat at one lag. That lag is the surviving family, and the whole ablation thread is indexed by it.
The census keeps four of them: 4, 5, 7 and 8, across thirty wrecked cuts on ten lattices. That is a small number of distinct answers for a table that size, and it is the reason a fifth would be worth having.
Why four is the number that matters
The exchange’s size is accounted for as one step of the control’s divergence, less about a fifth of the surviving hop’s own angle. The rule is right in sign on all seventeen rows it was fitted over.
Seventeen rows is not seventeen tests. The hop is nearly constant inside a lag, so seventeen rows carry eleven hop values in four clusters, and inside a cluster the coefficient still runs 0.12 to 0.29. A rule fitted on the hop is fitted over four numbers whatever the row count says.
That was the file’s own reading of itself rather than a criticism from outside, and it is stated beside the direction result, which does rest on seventeen rows because it is a difference between two labels rather than a fit to a number.
What a fifth cluster would be worth
A fifth hop is the first observation the rule has not already been fitted to. If it landed near the line the rule would have been tested; if it landed off, the rule would have been broken by one number.
The prediction was written down before the search: at a lag of 11 on a golden lattice the exchange should fall about six degrees short of one divergence step, and at 13 about four degrees long. That is specific enough to be wrong.
Where such a lag would have to come from
The surviving family is a contact family of the lattice — a survivor has to be a neighbour rather than any lag at all. So a cut keeping 11 needs a lattice with an 11 among its contact numbers, and a cut keeping 13 needs a 13.
On this ladder those are the golden 8/13 rung and the Lucas 7/11 rung, both at the fine end. The census cuts one rise on each. Twenty more rises were cut, ten a branch, running from inside those rungs down past the ladder’s finest.
What the golden branch returns
Every golden rise inside the 8/13 rung keeps 8 or 4. Three rises were cut there — 0.006, 0.0055 and 0.005 — and between them their wrecking offsets keep 8 at most of them and 4 at a few.
Not one keeps 13. The counter finds 13 among the contact numbers at all three, and the cut never leaves it standing at any offset at any of them.
And the survivor is never the shortest hop there
There is a sharper way to say the same thing. At every golden rise on a rung, the family left standing ranks second or worse by hop length — never first.
So the 13 is present, it is the shortest step on the surface at those rises, and it is never what survives. That is consistent with the census’s own finding that the survivor is not the shorter of the two contact steps, and it is the reason the golden half of the prediction has nothing to be tested on.
Below the rung, the stem stops being a lattice
The obvious next move is to keep going down. It does not work, and the way it fails is worth reporting.
Below the golden 8/13 rung’s fine end the settled divergence leaves the branch: the rises searched come back at 185.8°, 225.4°, 229.2°, 228.4°, 183.4° and 178.8°, between 41 and 92 degrees from the golden angle. Every rung of the ladder proper settles within 5.3 degrees of its branch angle, so those are not near-misses.
What the counter returns down there
The pairs are the other half of the evidence. Below the rung the counted pairs are 2/4, 8/16, 11/22 and 8/11, and the first three are not two consecutive terms of any additive sequence — they are a number and its double.
A counter still returns a pair there, which is exactly why the exclusion has to be made on the divergence rather than on whether a pair came back. A doubled pair is what a counter says about an arrangement with a rotational symmetry in it rather than about a lattice.
So the golden prediction is not merely unconfirmed
There is a difference between it was looked for and not found and there is nowhere to look, and this is the second. No golden lattice on this ladder keeps a lag of 11 or 13, and below the ladder there are no lattices at all in the sense this collection uses the word.
That is a fact about the rule that places organs rather than about the search. The rule settles a stem onto a branch over a range of rises and stops doing so below it, and the range it stops at is where the pairs with large numbers in them live.
Which is a constraint on the whole thread
Read forwards rather than backwards, this says something about what the ablation census can ever contain. The surviving lag comes from the contact families, the contact families come from the rung, and the rungs the ladder carries are 2/3, 3/5, 5/8 and 8/13 on one branch and 1/3, 3/4, 4/7 and 7/11 on the other.
The smaller number of each pair runs 1, 2, 3, 3, 4, 5, 7, 8. Those are the lags a cut can plausibly keep, and the census keeps four of them.
The larger number of a pair, and whether it ever survives
Stated that way the question becomes sharper than the one that was asked. It is not does anything keep 11 or 13? but does the larger counted number ever survive a cut?
On the golden branch the answer over twenty cut rises is no. On the Lucas branch it is yes, once, one rise below where the census stops — and that single case is what the whole search returned.
Why the census stopped where it did
The census’s ten lattices were chosen so that the same counted pair appears at more than one rise, which is what makes its decisive negative available: 4/7 appears twice and 5/8 four times, so the pair and the offset do not decide the survivor is a claim with rows on both sides.
They were not chosen to span the lags. Nobody had asked which lags a cut can keep, because the answer looked like a consequence of which lattices were in the table rather than like a fact about the rule.
It is a fact about the rule, and the way to see that is that the family a cut keeps is read from the stem itself rather than assigned. The census did not choose its lags; it recorded them.
What the search cost
Twenty rises, each cut at every offset out to the front and two past it: about eight minutes of stems, and the result is banked so that reading it again is free.
That is cheap for a search and it is worth saying that a search is a different kind of work from a sweep. A sweep visits every point of a stated range; a search goes looking, and its report has to include where it looked as well as what it found.
What was looked at, exactly
Ten rises on each branch. The golden list starts at 0.0060, inside the 8/13 rung, and runs down through 0.0055, 0.0050, 0.0046, 0.0044, 0.0042, 0.0040, 0.0038, 0.0035 and 0.0032. The Lucas list starts at 0.0090, inside the 7/11 rung, and runs down to 0.0032.
Three of the golden rises are on a rung and seven are below the ladder. Four of the Lucas rises are on a rung and six are below. So the search covered the whole of both fine ends and then some.
The negative is bounded, and the bound is stated
What is not claimed is that no golden lattice anywhere keeps 13. The claim is about this ladder, which is the region a stem grown by this rule settles onto a branch in, at the rises this search cut.
A finer step between 0.006 and 0.00482 could in principle find one. That is 27 rises at one per cent and about ten minutes, and it is the obvious way to make the negative tighter if anybody wants it tighter.
Why the prediction was branch-specific in the first place
The six degrees in the prediction came from arithmetic on a golden lattice: a hop at lag 11 on a golden lattice has a particular angle, and a fifth of it is a particular number.
That arithmetic does not transfer. The Lucas lattice that does keep 11 has a different divergence and therefore a different hop, so the number the prediction names cannot be checked and the rule it came from can. Confusing the two would be reading a prediction’s arithmetic as its content.
What a negative like this is for
It closes a direction. Anybody extending the exchange’s correction now knows that the golden branch cannot supply a fifth cluster, that the Lucas branch supplies exactly one, and that the region below the ladder supplies none because it supplies no lattices.
That is worth more than an unsuccessful search usually is, because it turns nobody has found one into there is one place and here it is.
The two halves of the search report differently
The golden half returns a bounded negative. The Lucas half returns a single positive at a rise of 0.006, on the 7/11 rung, whose settled divergence is 0.158 degrees from the Lucas angle.
Both are worth reporting and the second is the one that changed a number. It is the subject of its own reading, and the rule it tests survives it.
The other lattices the search passed over
Four Lucas rises sit on a rung: 0.0090, 0.0080, 0.0070 and 0.0060. The first three keep
7 at every offset that wrecks, which is what the census’s own l008 does, and the
fourth keeps 7 at three offsets and 11 at three more.
So the change happens between 0.007 and 0.006, inside the 7/11 rung and below the band that was cut whole across it. The band holds the survivor fixed at 7 across all 124 of its rises and the survivor changes twenty rises below its fine end.
That is a coincidence of design rather than a finding: the band was grown outwards from the handover until the divergence moved a twentieth of a degree, and it happens to stop above the rise where the family changes.
What is between 0.007 and 0.006
Nobody has looked. The search stepped from 0.0070 to 0.0060 in one move, so the rise at which the family changes on that rung is located to within a sixth of the rung and no better.
Narrowing it is nine rises at the five-decimal grid and about five minutes, and it would say whether the change is a transition at one rise — as the second wall going free turned out to be — or a stretch where both families occur. That question has an answer and it has not been asked.
Why a doubled pair is not a lattice
The counted pairs below the ladder deserve a sentence, because a reader could take 8/16 for an ordinary count. A lattice this collection would call one has a pair of coprime contact numbers, which is what two consecutive terms of an additive sequence always are.
8 and 16 are not coprime and 11 and 22 are not. A counter returns them because it reports the two families whose steps are shortest, and on an arrangement with a rotational symmetry the shortest two can be a family and its double.
That is why the branch test is made on the settled divergence and not on the pair. A pair that looks wrong is suggestive; a divergence 92 degrees from the branch angle is the measurement.
The search’s own refusal
One rise in twenty could not be read at all and the search records it rather than dropping it. A search that stopped at its first unreadable point would be reporting where the reading fails rather than where the lag is.
That distinction has bitten this collection before. The failure mode it keeps producing is absence — a figure that draws nothing, a tick array that comes back empty, a label placer that places nothing — and every one of them passed every check that asks whether what is there is right.
What a reader should carry
That the four lags the census keeps are not an accident of which lattices were in it. They are what the rule that places organs makes available, and the larger counted number of a pair never survives a cut on the branch that was searched.
And that a prediction can be well posed, specific and untestable — not because nobody tried, but because the object it is about does not occur.
What the picture at the top shows
Ten rows, one per golden rise searched, coarse at the top. Each row names the counted pair the stem shows, the divergence it settles to, and the lags its wrecking cuts leave standing.
The top three rows are on a rung and keep 8 or 4. The seven below are pale: their divergences are 41 to 92 degrees off the golden angle and their pairs are 2/4, 8/16, 11/22 and 8/11. Nothing anywhere in the block keeps 13.
The one line
Twenty rises cut at the fine end of both branches: no golden lattice on this ladder keeps a lag of 11 or 13, the survivor there ranks second or worse by hop length at every rise, and below the finest rung the stem stops settling onto its branch at all — so the golden half of the prediction has nothing to be tested on.
The Lucas branch supplies exactly one lattice that does, and it is one rise below where the census stops.
What links here
Computed from the collection, not written here: the essays that point at this one.
Shares its objects with
Essays that name at least two of the same things, and that neither author linked.
- Every rise of a band — both name ablation, claim testing, honest limits, lattice offset, negative result, parastichy pair, rise, rung
- Six lattices were not enough — both name ablation, claim testing, honest limits, lattice offset, negative result, parastichy pair, rise, rung
- The exception was already labelled — both name ablation, claim testing, honest limits, lattice offset, negative result, parastichy pair, rise, rung
- The front deepens down a rung — both name ablation, claim testing, honest limits, lattice offset, negative result, parastichy pair, rise, rung
- The offsets that never change — both name ablation, claim testing, honest limits, lattice offset, negative result, parastichy pair, rise, rung
- The shortest hop was a coin flip — both name ablation, claim testing, honest limits, lattice offset, negative result, parastichy pair, rise, rung
Named objects
A flat tag is an object no other essay names yet.
AblationClaim testingContact familyHonest limitsHop lengthIdentifiabilityLattice offsetNegative resultParastichy pairRiseRungSearch