In mathematical invariant theory, the catalecticant of a form of even degree is a polynomial in its coefficients that vanishes when the form is a sum of an unusually small number of powers of linear forms. It was introduced by Sylvester (1852); see Miller (2010). The word catalectic refers to an incomplete line of verse, lacking a syllable at the end or ending with an incomplete foot.
Binary forms
The catalecticant of a binary form of degree 2n is a polynomial in its coefficients that vanishes when the binary form is a sum of at most n powers of linear forms (Sturmfels 1993).
The catalecticant of a binary form can be given as the determinant of a catalecticant matrix (Eisenbud 1988), also called a Hankel matrix, that is a square matrix with constant (positive sloping) skew-diagonals, such as
\( {\begin{bmatrix}a&b&c&d&e\\b&c&d&e&f\\c&d&e&f&g\\d&e&f&g&h\\e&f&g&h&i\end{bmatrix}}. \)
Catalecticants of quartic forms
The catalecticant of a quartic form is the resultant of its second partial derivatives. For binary quartics the catalecticant vanishes when the form is a sum of 2 4th powers. For a ternary quartic the catalecticant vanishes when the form is a sum of 5 4th powers. For quaternary quartics the catalecticant vanishes when the form is a sum of 9 4th powers. For quinary quartics the catalecticant vanishes when the form is a sum of 14 4th powers. (Elliot 1915, p.295)
References
Eisenbud, David (1988), "Linear sections of determinantal varieties", American Journal of Mathematics, 110 (3): 541–575, doi:10.2307/2374622, ISSN 0002-9327, MR 0944327
Elliott, Edwin Bailey (1913) [1895], An introduction to the algebra of quantics. (2nd ed.), Oxford. Clarendon Press, JFM 26.0135.01
Sturmfels, Bernd (1993), Algorithms in invariant theory, Texts and Monographs in Symbolic Computation, Berlin, New York: Springer-Verlag, doi:10.1007/978-3-211-77417-5, ISBN 978-3-211-82445-0, MR 1255980
Sylvester, J. J. (1852), "On the principles of the calculus of forms", Cambridge and Dublin Mathematical Journal: 52–97
Undergraduate Texts in Mathematics
Graduate Studies in Mathematics
Hellenica World - Scientific Library
Retrieved from "http://en.wikipedia.org/"
All text is available under the terms of the GNU Free Documentation License
