The Atanasov--Ranganathan construction on row 05 #
Row 05 is AR's sixth genus-five family: two bananas, each attached by one leg to each of the two opposite vertices of a four-cycle.
e0, e1 : 0 == 1 e2 : 2 -> 0 e3 : 1 -> 3
e4 : 2 -> 5 e5 : 3 -> 5 e9 : 4 -> 3 e7 : 2 -> 4 (the square)
e6 : 5 -> 7 e8 : 4 -> 6 e10, e11 : 6 == 7
AR's own figure does not use a core-supported divisor: two of its four chips
sit at interior points of a leg, at an offset equal to another leg's length.
The certificate here is therefore a marked script
(Utilities/Subdivision/SplitRampScript.lean), which bends downward
at the chip and lets the chip pay for the kink.
The proof below uses the marked divisor displayed in the source and a script that bends at each interior chip. The chamber hypotheses ensure that the local configuration lemmas apply.
On chamber A -- |e2| ≤ |e3| and |e6| ≤ |e8| -- the displayed divisor is
D = [2] + [5] + (e3 at offset |e2| from 1) + (e8 at offset |e8| - |e6| from 4)
and the six chip-free vertices fall into three pictures:
{0, 1}and{6, 7}-- AR's seventh picture, a banana pair whose two arms have equal length (|e2|on the left,|e6|on the right). That equality is exactly what the interior chip placement buys.{3, 4}-- AR's third picture, a chip-free pair with two chip arms each, read throughConfigurationMarkedThree: vertex3's arms are the far half ofe3and the slote5, vertex4's aree7and the near half ofe8.
The other three chambers are the images of this one under the two leg swaps, so
GenusFiveRow05Symmetry and ClosedOrbit.closedConstruction_of_chamber finish
the closed orthant.
The two marks #
The left chip sits on e3 at distance |e2| from vertex 1; the right chip
sits on e8 at distance |e6| from vertex 6, i.e. at offset |e8| - |e6|
from vertex 4.
Offset of the left interior chip along slot 3, measured from vertex 1 and equal to the length of slot 2.
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Offset of the right interior chip along slot 8, measured from vertex 4 using truncated subtraction of the length of slot 6.
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- AtanasovRanganathan.GenusFiveRow05.markR d = d.length 8 - d.length 6
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The marked offsets on slots 3 and 8; every other slot receives offset zero.
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The four nested-min heights of the pair {3, 4} #
Vertex 3's arm minimum: the far half of e3, and e5.
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Vertex 4's arm minimum: e7, and the near half of e8.
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The partner height, shared by both readings of the pair.
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The height at vertex 3 when 3 is the target.
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The height at vertex 4 when 4 is the target.
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The four height profiles #
The left banana pair {0, 1}, both arms of length |e2|.
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The right banana pair {6, 7}, both arms of length |e6|.
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The configuration-3 pair read at the target 3.
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The configuration-3 pair read at the target 4.
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The script #
The potential of a height profile, read at the canonical class representative so that class invariance is definitional.
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- AtanasovRanganathan.GenusFiveRow05.rowPotential d h v = -↑(h (d.rep v))
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The script's value at each mark: zero on the two marked slots (the chips sit at the ambient level), the tail's own value elsewhere.
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Class constancy of a profile #
The two marked slots, spelled out #
Admissibility of the two marks #
mark 3 ≤ |e3| is the chamber inequality |e2| ≤ |e3|; the degenerate cases
mark = 0 and mark = length are exactly where the profile's height at that
end vanishes.
Each slot as one or two ordinary arms #
Tail contribution of a slot to the marked script: a positive marked offset cuts the ramp at height zero; otherwise use the complete slot.
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Head contribution of a slot to the marked script, using the segment beyond an interior mark on slots 3 and 8 and the complete slot otherwise.
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The endpoint ledger, vertex by vertex #
The total incident-slot contribution at each row-05 core vertex, with the two marked slots evaluated by their split-ramp formulas.
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The displayed divisor #
The two core-supported chips of the row-05 divisor, one each at vertices 2 and 5; the remaining chips lie at the marks.
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AR's divisor on chamber A: chips at the two square vertices 2 and 5,
and one chip inside each of the two marked legs.
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The core-class weight of the divisor: the two square chips, plus each marked chip when its mark has reached an end of its slot.
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The two chip allocations #
The banana pictures charge the divisor exactly as it stands; the configuration-3 pair moves each collapsed arm's chip onto the centre it feeds, which is a transfer inside a contracted class and so leaves every class sum alone.
Core chip allocation for the central pair: redistribute the base weight across contracted slots 3, 5, and 7 before applying the height script.
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The slot forms of the two marked legs, under a profile #
The tail of the left marked leg, with the split kept: the profiles of the
pair {3, 4} have a nonzero height at the far end.
The core-class weights, vertex by vertex #
The banana pair {0, 1} #
The per-vertex coefficient of the left banana script.
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The vertex of the class of 0 that owns the delivered chip.
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The banana pair {6, 7} #
Expanded core coefficients after applying the right-banana height script to the base weight;
rbCoeff_eq relates this formula to the endpoint contributions.
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Representative receiving the chip for vertex 6: choose vertex 4 when slot 8 is contracted, and vertex 6 otherwise.
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Representative receiving the chip for vertex 7: choose vertex 5 when slot 6 is contracted, and vertex 7 otherwise.
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The configuration-3 pair {3, 4}, read at the target 3 #
Expanded coefficients of the allocated central-pair divisor after the script targeting
vertex 3; t3Coeff_eq identifies the endpoint-sum formula.
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The vertex of the class of 3 that owns the delivered chip: the partner,
when the middle slot has collapsed and the partner's arms are the shorter.
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The configuration-3 pair {3, 4}, read at the target 4 #
Expanded coefficients of the allocated central-pair divisor after the script targeting
vertex 4; t4Coeff_eq identifies the endpoint-sum formula.
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Representative for the vertex-4 target: use vertex 3 when slot 9 is contracted and the second arm is longer, and vertex 4 otherwise.
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From the per-vertex coefficients to the residual #
The hypotheses of the kink lemma at a mark strictly inside its slot.
The local Dhar move. With the profile's four mark bounds and a chip allocation whose class sums are the divisor's, the marked script leaves an effective residual at the named centre.
The owners lie in their centres' classes #
Every contracted core class is reached #
Chamber A, and the whole closed orthant #
AR's sixth family on row 05. The paper's own divisor -- two chips on the square and one inside each of the two marked legs -- has rank at least one on every nonloopy forest face, all four chambers at once.