The band was not the sampling
Worth reading first: A stem coarse enough to cut · Counting the spirals · A head is a set of points.
Five rises in the middle of the 2/3 rung do not settle. They stick on exactly three eighths of a turn — 135.0000° to four decimal places — and wobble about it by 0.79° to 1.60°, while a counter shown their positions still returns the rung’s own pair and cannot tell them from a settled lattice.
The band was bounded there and not explained, and the obvious worry was recorded with it. The coarse ladder is swept at five thousandths of rise. That is coarse enough that a band of the same kind could sit inside any finer rung and never be sampled — in which case the 2/3 result would be a fact about the ladder’s step rather than about the 2/3 rung.
This essay runs that test. Twenty-three rises from 0.030 down to 0.019, in steps of five ten-thousandths, across the whole of the 3/5 rung. Nothing locks.
The 3/5 rung is the right one to test on and not merely the convenient one. It is the rung immediately finer than the coarse ladder’s range, so if stability at a low-denominator angle is something that fades as the front deepens, this is where the fading would be least complete. Testing on a much finer rung would risk finding nothing for a reason that has nothing to do with the band — the front there is deep enough that no low-denominator angle could plausibly be stable — and a negative from that rung would prove less.
What was swept
Every rise on the rung, at a tenth of the resolution that found the band. All twenty-three are counted at 3 and 5 spirals, which is what makes the sweep a sweep of one rung rather than a walk across two.
All twenty-three settle. The largest wander of the divergence over the last stretch of any of them is 0.221°, against a settling threshold that the coarse band exceeds by a factor of four to eight.
That margin is what makes the result readable rather than marginal. A negative that depended on the threshold — largest wander 0.6° against a band starting at 0.79° — would be a statement about where a line was drawn. A factor of three and a half between the worst settled rise here and the quietest locked rise there is not a line-drawing question, and it means the two populations do not overlap at all rather than merely separating on average. The same distinction between a threshold result and a separation is what decides whether a score is worth quoting.
The divergence slides smoothly through the rung. No rise sits on a rational; no rise sits on a value the neighbouring rises do not approach continuously; there is no interval of any width in which the behaviour changes kind.
The slide itself is worth noticing as a positive rather than only as the absence of a band. Across twenty-three rises the divergence moves by 2.3°, monotonically, while the counted pair never changes — which is the same phenomenon the ablation sweeps depend on measured on a different rung and at ten times the resolution. A rung is not a plateau in the geometry; it is a plateau only in what a counter reports about the geometry, and this sweep is the finest confirmation of that the collection has.
Why a tenth is the right factor
The band on the coarse rung is five consecutive rises wide at a step of five thousandths — an interval of about 0.025 in rise, which is a quarter of that rung’s whole width. A feature that occupied a quarter of the 3/5 rung would span about six of the twenty-three samples here.
So the sweep is not merely finer than the one that found the band; it is fine enough that a band of the same relative width would be sampled six times over. For the band to have hidden here it would have to be more than an order narrower relative to its rung than the one on the 2/3 rung is, which is a different claim from the one the worry was about.
Stating the excluded width matters because “swept finer, found nothing” is the weakest form of a negative and the easiest to overstate. What is excluded here is a feature occupying more than about a twentieth of the rung. What is not excluded is a feature at a single rise between two samples, or one an order narrower than the coarse band. Neither of those is what the worry proposed, and both would be a different phenomenon from the one being tested for.
That is the honest form of the negative: a band like the coarse one is not there. A far narrower band, or one at a rise between two samples, is not excluded by twenty-three points and could not be by any finite sweep.
What it does to the coarse result
It makes it a property of that rung rather than an artefact of the ladder, and that is a promotion rather than a demotion.
A negative result is worth what its margin is worth, and this one has a margin in two directions.
The first is how close anything came. The settling test bounds how far a stem’s divergences wander over its last stretch, and the coarse band’s members wander by 0.79° to 1.60°. The largest wander anywhere in this sweep is 0.221° — under a third of the smallest coarse-band value, at the worst of twenty-three rises. This is not a sweep that found everything comfortably inside a threshold with one or two rises pressed up against it. Nothing on this rung is near the condition being looked for.
The second is how large a band would have to be to hide here. The coarse band is five consecutive rises at a step of five thousandths, a stretch of rise 0.020 wide. The whole of the 3/5 rung is 0.011 wide. A band of that size does not fit inside this rung at all. What a proportionally narrower one would do to the sampling is the argument made above; what matters here is the shape it would leave — a run of neighbouring rises all wandering past the threshold together, which is the most conspicuous pattern this sweep is capable of producing and the last one anybody would miss.
So the sweep is not merely quiet. It is quiet in a place where the thing it was looking for would have been loud, which is the difference between a null and an absence of evidence, and the whole reason the sweep was run at a tenth of the step rather than at the same one.
What it cannot do is speak for rungs it never visited. The claim is about the 3/5 rung at ten times the coarse resolution, and the honest generalisation is narrow: whatever produces a locked band is not something every rung has and the ladder’s step was hiding.
A locked band that appeared at every resolution on every rung would have said something about the sweep. A locked band that appears where it was first found and not one rung finer says something about the 2/3 rung: that the rule prefers a particular rational there, at a place on the ladder where the arrangement has few enough organs in its front for a low-denominator angle to be a stable answer.
There is a reading of that which connects it to the rest of the collection. A front of three organs offers very few arrangements for the rule to choose among, and the number of arrangements a front can pass through is the same quantity that decides whether a cut stem can reach its own mirror. Both are statements about a front shallow enough that the rule’s options are countable. Whether they are the same fact is not established here and would need the wobble measured rather than bounded.
What it does not settle
Three things, and they are the questions the coarse essay left rather than new ones.
Why three eighths. Nothing here says why the rule prefers that rational over its neighbours. The finer rung has rationals of similar denominator available and approaches none of them — the 3/5 rung’s divergences pass within a degree of several eighths and ninths on their way through, and settle at none of them. So whatever selects three eighths on the coarse rung is not simply proximity, or the finer rung would show the same pull weakly rather than not at all.
Whether the wobble has a period. The coarse band wobbles by 0.79° to 1.60° about its rational, and nobody has asked whether that wobble is itself periodic or merely noisy. This sweep has no locked rises to ask it of. The question is not idle: a periodic wobble would make the band a cycle rather than a fixed point, and this collection has already found a wrecked stem settling into a cycle of four rather than onto an angle. If the band turned out to be the same object seen from a different side, the coarse rung would have one phenomenon instead of two.
And whether coarser rungs below 2/3 do the same. The ladder continues below the coarse rung, and no sweep of any resolution has gone there. If the reading is that low-denominator angles become stable when the front is shallow, the rungs below should show it more strongly rather than less — and a 1/2 rung, whose front is two organs, is where the reading would be most exposed. That sweep is cheap: coarse stems settle quickly and there are few rises to cover. It has not been run because nothing until now made it a question with an answer worth having, and the essay that established the coarse rung’s eligibility stopped at the boundary of what a cut could be made on rather than at the boundary of the ladder.
Four controls
One rung, checked rather than assumed. The sweep’s own generator refuses to draw a ladder whose rises do not all return the same pair, so a sweep that wandered across a rung boundary would stop the build rather than average two rungs together.
The settling test is the same one. A rise counts as settled by the criterion every other run on this site uses, at the same threshold, so the comparison between the two rungs is a comparison of like with like.
The stems are the same construction. Same rule, same node count, same azimuth grid; only the rise differs across the sweep, and only the rung differs between the two sweeps. That last clause is the one worth pressing on, because a finer rung packs more organs into the same stem and could in principle be settling better for a reason that has nothing to do with rationals — simply more organs of settling per unit of rise. If that were the explanation the wander would fall smoothly across the rung as the rise falls, and it does not: the largest and smallest wanders here are not at the two ends.
And the negative is not a threshold artefact. The largest wander here is 0.221°; the coarse band’s smallest is 0.79°. The two do not come close enough for the answer to depend on where the threshold is put.
Where this leaves it
The band is real, it is where it was found, and it is not a sampling artefact of the ladder. That is three statements and the sweep establishes the third, which was the one in doubt.
What it also does is retire a worry that would otherwise have sat under every result on the coarse rung. The essays that cut stems there exclude the locked rises from their tables, and that exclusion is only defensible if the locking is a real property of those rises rather than a resolution effect that the same tables would show elsewhere at a finer step. It is real, and they are.
One more thing follows from the negative and is easy to miss. If the 3/5 rung has no locked band, then every rise on it is available to be cut — the whole rung is eligible, where the coarse rung loses five of its nineteen rises to the band before any ablation can be attempted. Finer rungs are therefore cheaper to sweep per usable rise as well as more informative, which is an argument for the finer sweeps this collection keeps deferring on cost.
A negative result that costs twenty-three settled stems and closes a standing doubt is a cheap one. The alternative was leaving the doubt open and hoping nobody asked.
It is also a template. Every sweep in this collection has a step, and every step is a claim that nothing interesting happens between two samples. That claim is almost never tested, because testing it means running the same sweep an order finer and reporting that nothing changed — which produces no new figure and no new result. This one produced both only because there was a specific feature to look for. The rung sweeps that found the survivor changing hands had the same shape and came out the other way, and the pair of them together is a better argument for sweeping finely than either alone.
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.
- A stem too fine to settle — both name counting blind, claim testing, control, honest limits, lattice, measurement, negative result, parastichy pair, the placement rule, rise, rung
- One offset, two answers — both name claim testing, control, honest limits, lattice, measurement, negative result, parastichy pair, the placement rule, rise, rung
- The front deepens down a rung — both name claim testing, control, honest limits, lattice, measurement, negative result, parastichy pair, the placement rule, rise, rung
- Two accounts of one number — both name counting blind, claim testing, honest limits, lattice, measurement, negative result, parastichy pair, the placement rule, rise, rung
- A stem on the other branch — both name counting blind, honest limits, lattice, measurement, metastability, parastichy pair, the placement rule, rise, rung
- A survivor has to be a neighbour — both name counting blind, honest limits, lattice, measurement, negative result, parastichy pair, the placement rule, rise, rung
Named objects
A flat tag is an object no other essay names yet.
Counting blindClaim testingControlDivergence angleHonest limitsLatticeMeasurementMetastabilityNegative resultParastichy pairThe placement ruleRational divergenceRiseRungScatter tolerance