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LeanPool.BrillNoetherGraphs.Bananas.Theta.ThetaTransmissionCases

Elementary rows in the theta transmission case table #

This module starts the direct rank-difference portion of Proposition 4.5. The remaining task is the exhaustive classification of the default case; the exceptional rows below are graph-independent once their stated divisor-class conditions hold.

The marked second rank difference of the zero divisor is one.

theorem Bananas.transmission_eq_sub_two_of_linearEquiv_two_u {M : TwiceMarked} {D : CFDiv M.graph} {tau : ℤ → ℤ} (t : ℤ) (hTau : IsTransmissionPermutation M D tau) (hClass : linearEquiv M.graph (D + t • (oneChip M.u - oneChip M.v)) (2 • oneChip M.u)) :
tau t = t - 2

The first row in Proposition 4.5: if the degree-two twist at t is 2u, then the transmission permutation takes t to t - 2.

The second row in Proposition 4.5: if the degree-two twist at t is u+w with w in neither marked one-chip class, then the transmission value is t - 1.

The fourth row in Proposition 4.5: writing the reflected class of u as K-u, a twist equivalent to v + (K-u) forces transmission value t + 2.

The exhaustive default row #

Proposition 4.5's t - 2 exceptional class, stated independently of a chosen transmission permutation.

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    Proposition 4.5's t - 1 exceptional class. The two inequalities in the paper mean that the residual chip belongs to neither marked degree-one class.

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      Proposition 4.5's t + 1 exceptional class. Saying that w is neither reflected marked point is precisely saying that neither marked pair with w is canonical.

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        Proposition 4.5's t + 2 exceptional class, with the reflected class bar u written coordinate-freely as K-u.

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          The fifth row of Proposition 4.5 at the rank-theoretic level. On a rigid theta graph, a degree-two class outside the four exceptional classes has rank pattern (0,-1,-1,-1) after deleting neither, either, or both marked chips.

          The exhaustive default row of Proposition 4.5: if the degree-two twist at t belongs to none of the four exceptional divisor classes, its transmission value is t.

          TeX label: prop-thetaTransChar (Proposition 4.5).

          The complete rowwise transmission table for a rigid theta marking. The four exception predicates are the coordinate-free versions of the paper's classes 2u, u+w, v+w, and v+\bar u; the final implication is the exhaustive default row. Their mutual exclusivity is not needed to state or use the table, since each implication is proved directly from the corresponding rank difference.