Corrigendum to “On the cactus rank of cubics forms” [J. Symb. Comput. 50 (2013) 291–297, (S0747717112001332), (10.1016/j.jsc.2012.08.001)]

The main results in Bernardi and Ranestad (2013) concern minimal length apolar subschemes to cubic forms. Apolarity is defined via an action on polynomials by a dual polynomial ring. In the paper the action is defined as differentiation: [Formula presented] acting on [Formula presented] by [Formula presented] Which means that [Formula presented]. Alternatively one may define the action by contraction, which means that [Formula presented]. With the action defined by differentiation, the proof of Lemma 2 is incorrect, however with the action defined by contraction, the proof is correct. Differentiation should therefore be substituted by contraction in the paper, since this lemma is used throughout. We thank Joachim Jelisiejew for pointing out this error to us. Alessandra Bernardi: Writing – original draft. Kristian Ranestad: Writing – original draft.