Converse-invariant orientations of trees with maximum degree at least three

From papers

Let DD be an orientation of a tree with maximum degree at least 33. Write D-D for the converse orientation, and say that DD is converse invariant when it has the same number of copies in every tournament as D-D. The bridge-mirroring operation is the operation defined in the paper that mirrors an oriented bridge; recursively applying it produces orientations from an orientation of a path.

Conjecture on converse-invariant tree orientations. DD is converse invariant if and only if

DDD\cong -D

or DD can be obtained by applying the bridge-mirroring operation recursively to an orientation of a path.

The paper establishes this characterization for orientations of trees with diameter bounded by three. The conjecture proposes that the same description holds for all orientations of trees with maximum degree at least 33.

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Sources & referencesView supporting material

Primary source

Jiangdong Ai, Gregory Gutin, Hui Lei, Anders Yeo and Yacong Zhou, “Number of Subgraphs and Their Converses in Tournaments and New Digraph Polynomials”, arXiv:2407.17051 (2024).

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