Unexpected hypersurfaces of type $(d+k,d)$
Abstract
Unexpected hypersurfaces arise when vanishing in points of a set and higher-order vanishing along a general linear subspace fails to impose the expected number of independent conditions on forms of a fixed degree. The phenomenon was first observed for planar curves by Cook, Harbourne, Migliore and Nagel. This paper shows a syzygy-based construction of, possibly unexpected, hypersurfaces of degree in , vanishing along a codimension two general linear subspace with multiplicity ; thus generalizing the work of Trok and the previous work of the last two authors. Our framework unifies the classical planar cases with higher-dimensional examples, including Trok's construction. We give a sufficient criterion for unexpectedness (via the splitting behaviour the syzygy bundles of the powers of the Jacobian ideal, associated with the hyperplane arrangement dual to ) and provide explicit examples in and .
Keywords
Cite
@article{arxiv.2511.10772,
title = {Unexpected hypersurfaces of type $(d+k,d)$},
author = {Marek Janasz and Grzegorz Malara and Halszka Tutaj-Gasińska},
journal= {arXiv preprint arXiv:2511.10772},
year = {2025}
}
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24 pages