e/Invariant factorization of LPDOs

Information
has gloss	eng: Beals-Kartashova-factorization (also called BK-factorization) is a constructive procedure to factorize a bivariate operator of the arbitrary order and arbitrary form. Correspondingly, the factorization conditions in this case also have polynomial form, are invariants and coincide with Laplace invariants for bivariate hyperbolic operator of the second order. The factorization procedure is purely algebraic, the number of possible factirzations depends on the number of simple roots of the Characteristic polynomial (also called symbol) of the initial LPDO and reduced LPDOs appearing at each factorization step. Below the factorization procedure is described for a bivariate operator of the arbitrary form, of the order 2 and 3. Explicit factorization formulas for an operator of the order n can be found in General invariants are defined in and invariant formulation of the Beals-Kartashova factorization is given...
lexicalization	eng: Invariant factorization of LPDOs
instance of	e/Differential operator