On the irreducibility of Hessian loci of cubic hypersurfaces

We study the problem of the irreducibility of the Hessian variety ${\mathcal {H}}_f$ associated with a smooth cubic hypersurface $V(f)\subset {\mathbb {P}}^n$ . We prove that when $n\leq 5$ , ${\mathcal {H}}_f$ is normal and irreducible if and only if f is not of Thom-Sebas...

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Main Authors: Davide Bricalli, Filippo Francesco Favale, Gian Pietro Pirola
Format: Article
Language:English
Published: Cambridge University Press 2025-01-01
Series:Forum of Mathematics, Sigma
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Online Access:https://www.cambridge.org/core/product/identifier/S2050509425000362/type/journal_article
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author Davide Bricalli
Filippo Francesco Favale
Gian Pietro Pirola
author_facet Davide Bricalli
Filippo Francesco Favale
Gian Pietro Pirola
author_sort Davide Bricalli
collection DOAJ
description We study the problem of the irreducibility of the Hessian variety ${\mathcal {H}}_f$ associated with a smooth cubic hypersurface $V(f)\subset {\mathbb {P}}^n$ . We prove that when $n\leq 5$ , ${\mathcal {H}}_f$ is normal and irreducible if and only if f is not of Thom-Sebastiani type (i.e., if one cannot separate its variables by changing coordinates). This also generalizes a result of Beniamino Segre dealing with the case of cubic surfaces. The geometric approach is based on the study of the singular locus of the Hessian variety and on infinitesimal computations arising from a particular description of these singularities.
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spelling doaj-art-acaf2f1935e04ecc9c50c8bfe096cf0d2025-08-20T03:53:43ZengCambridge University PressForum of Mathematics, Sigma2050-50942025-01-011310.1017/fms.2025.36On the irreducibility of Hessian loci of cubic hypersurfacesDavide Bricalli0https://orcid.org/0009-0009-8109-9551Filippo Francesco Favale1https://orcid.org/0000-0002-2924-184XGian Pietro Pirola2https://orcid.org/0000-0002-2007-2525Università degli Studi di Pavia, Dipartimento di Matematica, Via Adolfo Ferrata 5, 27100 Pavia, Italy; E-mail: INdAM (GNSAGA); E-mail:Università degli Studi di Pavia, Dipartimento di Matematica, Via Adolfo Ferrata 5, 27100 Pavia, Italy; E-mail:Università degli Studi di Pavia, Dipartimento di Matematica, Via Adolfo Ferrata 5, 27100 Pavia, ItalyWe study the problem of the irreducibility of the Hessian variety ${\mathcal {H}}_f$ associated with a smooth cubic hypersurface $V(f)\subset {\mathbb {P}}^n$ . We prove that when $n\leq 5$ , ${\mathcal {H}}_f$ is normal and irreducible if and only if f is not of Thom-Sebastiani type (i.e., if one cannot separate its variables by changing coordinates). This also generalizes a result of Beniamino Segre dealing with the case of cubic surfaces. The geometric approach is based on the study of the singular locus of the Hessian variety and on infinitesimal computations arising from a particular description of these singularities.https://www.cambridge.org/core/product/identifier/S2050509425000362/type/journal_article14J7014M1214J1714J3014J35
spellingShingle Davide Bricalli
Filippo Francesco Favale
Gian Pietro Pirola
On the irreducibility of Hessian loci of cubic hypersurfaces
Forum of Mathematics, Sigma
14J70
14M12
14J17
14J30
14J35
title On the irreducibility of Hessian loci of cubic hypersurfaces
title_full On the irreducibility of Hessian loci of cubic hypersurfaces
title_fullStr On the irreducibility of Hessian loci of cubic hypersurfaces
title_full_unstemmed On the irreducibility of Hessian loci of cubic hypersurfaces
title_short On the irreducibility of Hessian loci of cubic hypersurfaces
title_sort on the irreducibility of hessian loci of cubic hypersurfaces
topic 14J70
14M12
14J17
14J30
14J35
url https://www.cambridge.org/core/product/identifier/S2050509425000362/type/journal_article
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