Inverting catalecticants of ternary quartics

  • L. Brustenga i Moncusí University of Copenhagen, Denmark
  • E. Cazzador University of Oslo, Norway
  • R. Homs Technical University of Munich, Germany


We study the reciprocal variety to the LSSM of catalecticant matrices associated with ternary quartics. With numerical tools, we obtain 85 to be its degree and 36 to be the ML-degree of the LSSM. We provide a geometric explanation to why equality between these two invariants is not reached, as opposed to the case of binary forms, by describing the intersection of the reciprocal variety and the orthogonal of the LSSM in the rank loci. Moreover, we prove that only the rank-$1$ locus, namely the Veronese surface ν4(P2), contributes to the degree of the reciprocal variety.