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Laplace Equations and the Weak Lefschetz Property

Published online by Cambridge University Press:  20 November 2018

Emilia Mezzettiaaa
Affiliation:
Dipartimento di Matematica e Geoscienze, Università di Trieste, Via Valerio 12/1, 34127 Trieste, Italy, e-mail: mezzette@units.it
Rosa M. Miré-Roig
Affiliation:
Facultat de Matemàtiques, Department d'Algebra i Geometria, Gran Via des les Corts Catalanes 585, 08007 Barcelona, Spain, e-mail: miro@ub.edu
Giorgio Ottaviani
Affiliation:
Dipartimento di Matematica, Università di Firenze, Viale Morgagni 67/A I-50134 Firenze, Italy, e-mail: ottavian@math.unifi.it
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Abstract

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We prove that $r$ independent homogeneous polynomials of the same degree $d$ become dependent when restricted to any hyperplane if and only if their inverse system parameterizes a variety whose $(d-1)$- osculating spaces have dimension smaller than expected. This gives an equivalence between an algebraic notion (called the Weak Lefschetz Property) and a differential geometric notion, concerning varieties that satisfy certain Laplace equations. In the toric case, some relevant examples are classified, and as a byproduct we provide counterexamples to Ilardi's conjecture.

Type
Research Article
Copyright
Copyright © Canadian Mathematical Society 2013

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