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Conormal Rank of Subvarieties of Grassmannians
Abstract
The cotangent space to any subvariety of a Grassmannian is naturally identified with a space of linear homomorphisms. We use this to define a new statistic on a subvariety of a Grassmannian, called \emph{conormal rank}. We show that Chow--Lam forms and their natural generalizations have low conormal rank, and moreover that hypersurfaces of sufficiently low conormal rank are all of this form, generalizing a result of Gelfand--Kapranov--Zelevinsky. We also compute the conormal rank of many families of varieties, including Schubert varieties, torus orbit closures, and positroid varieties.
Related
BibTeX
@misc{pratt2026conormal,
title = {{Conormal Rank of Subvarieties of Grassmannians}},
author = {Elizabeth Pratt},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.24694},
eprint = {2609.24694},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.24694},
}
RIS
TY - UNPB
TI - Conormal Rank of Subvarieties of Grassmannians
AU - Elizabeth Pratt
PY - 2026
DA - 2026/09/21
PB - arXiv
DO - 10.48550/arxiv.2609.24694
UR - https://arxiv.org/abs/2609.24694
AB - The cotangent space to any subvariety of a Grassmannian is naturally identified with a space of linear homomorphisms. We use this to define a new statistic on a subvariety of a Grassmannian, called \emph{conormal rank}. We show that Chow--Lam forms and their natural generalizations have low conormal rank, and moreover that hypersurfaces of sufficiently low conormal rank are all of this form, generalizing a result of Gelfand--Kapranov--Zelevinsky. We also compute the conormal rank of many families of varieties, including Schubert varieties, torus orbit closures, and positroid varieties.
ER -