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Divisors and harmonic morphisms on metric graphs of pseudocompact type
Abstract
A metric graph is of pseudocompact type if identifying parallel edges produces a tree. We give a constructive proof that, for such graphs, divisorial d-gonality is equivalent to the existence of a degree d harmonic morphism to a tree. This mirrors the algebraic correspondence, for curves of compact type, between limit linear series of dimension one and admissible covers. We also deduce lifting results for positive-rank divisors, with a genus-preserving refinement when identifying parallel edges produces a path. Finally, we study the Brill-Noether theory in the path case.
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BibTeX
@misc{mascuch2026divisors,
title = {{Divisors and harmonic morphisms on metric graphs of pseudocompact type}},
author = {Benjamin Mascuch and Montserrat Teixidor i Bigas},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2609.38821},
eprint = {2609.38821},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.38821},
}
RIS
TY - UNPB
TI - Divisors and harmonic morphisms on metric graphs of pseudocompact type
AU - Benjamin Mascuch
AU - Montserrat Teixidor i Bigas
PY - 2026
DA - 2026/10/01
PB - arXiv
DO - 10.48550/arxiv.2609.38821
UR - https://arxiv.org/abs/2609.38821
AB - A metric graph is of pseudocompact type if identifying parallel edges produces a tree. We give a constructive proof that, for such graphs, divisorial d-gonality is equivalent to the existence of a degree d harmonic morphism to a tree. This mirrors the algebraic correspondence, for curves of compact type, between limit linear series of dimension one and admissible covers. We also deduce lifting results for positive-rank divisors, with a genus-preserving refinement when identifying parallel edges produces a path. Finally, we study the Brill-Noether theory in the path case.
ER -