diffalg(deprecated)/preparation_polynomial - Maple Help

diffalg

 preparation_polynomial
 compute preparation polynomial

 Calling Sequence preparation_polynomial (p, a, R, 'm' ) preparation_polynomial (p, A=a, R, 'm' )

Parameters

 p - differential polynomial in R a - regular differential polynomial in R R - differential polynomial ring m - (optional) name A - derivative of order zero in R

Description

 • Important: The diffalg package has been deprecated. Use the superseding package DifferentialAlgebra instead.
 • The function preparation_polynomial computes a preparation polynomial of p with respect to a.
 • The preparation polynomial of p with respect to a is a sort of expansion of p according to mparama and its derivatives. It plays a prominent role in the determination of the essential components of the radical differential ideal generated by a single differential polynomial.
 • A differential polynomial a is said to be regular if it has no common factor with its separant. This property is therefore dependent on the ranking defined on R.
 • If A is omitted, the preparation polynomial appears with an  indeterminate  (local variable) looking like  _A.
 • If A is  specified, the preparation polynomial is in the  differential indeterminate A. Then, A, nor its derivatives, should appear in p nor a.
 • Assume that preparation_polynomial(p, a, R, 'm') = $\mathrm{c1}\mathrm{M1}\left(\mathrm{_A}\right)+\mathrm{....}+\mathrm{ck}\mathrm{Mk}\left(\mathrm{_A}\right)$, where the Mi are differential monomials in $\mathrm{_A}$ and the $\mathrm{ci}$ are polynomials in R. Then
 - $mp=\mathrm{c1}\mathrm{M1}\left(a\right)+\mathrm{....}+\mathrm{ck}\mathrm{Mk}\left(a\right)$, where m belongs to R.
 - The $\mathrm{ci}$ are not reduced to zero by a, and therefore do not belong to the general component of a.
 - m is a power product of factors of the initial and separant of a).
 • The command with(diffalg,preparation_polynomial) allows the use of the abbreviated form of this command.

Examples

Important: The diffalg package has been deprecated. Use the superseding package DifferentialAlgebra instead.

The preparation polynomial is used to determine the essential singular zeros of a differential polynomial.

 > $\mathrm{with}\left(\mathrm{diffalg}\right):$
 > $R≔\mathrm{differential_ring}\left(\mathrm{derivations}=\left[x,y\right],\mathrm{ranking}=\left[u,A\right]\right):$
 > $p≔16u\left[x,y\right]\left({u\left[x,x\right]}^{2}-{u\left[y,y\right]}^{2}+u\left[y,y\right]-u\left[x,x\right]\right)+{u\left[\right]}^{2}\left(4u\left[\right]-{x}^{2}-{y}^{2}\right)$
 ${p}{≔}{16}{}{{u}}_{{x}{,}{y}}{}\left({{u}}_{{x}{,}{x}}^{{2}}{-}{{u}}_{{y}{,}{y}}^{{2}}{-}{{u}}_{{x}{,}{x}}{+}{{u}}_{{y}{,}{y}}\right){+}{{u}\left[\right]}^{{2}}{}\left({-}{{x}}^{{2}}{-}{{y}}^{{2}}{+}{4}{}{u}\left[\right]\right)$ (1)
 > $\mathrm{equations}\left(\mathrm{Rosenfeld_Groebner}\left(\left[p\right],R\right)\right)$
 $\left[\left[{-}{{x}}^{{2}}{}{{u}\left[\right]}^{{2}}{-}{{y}}^{{2}}{}{{u}\left[\right]}^{{2}}{+}{4}{}{{u}\left[\right]}^{{3}}{+}{16}{}{{u}}_{{x}{,}{x}}^{{2}}{}{{u}}_{{x}{,}{y}}{-}{16}{}{{u}}_{{x}{,}{y}}{}{{u}}_{{y}{,}{y}}^{{2}}{-}{16}{}{{u}}_{{x}{,}{x}}{}{{u}}_{{x}{,}{y}}{+}{16}{}{{u}}_{{x}{,}{y}}{}{{u}}_{{y}{,}{y}}\right]{,}\left[{-}{{x}}^{{2}}{-}{{y}}^{{2}}{+}{4}{}{u}\left[\right]\right]{,}\left[{u}\left[\right]\right]\right]$ (2)
 > $\mathrm{preparation_polynomial}\left(p,u\left[\right],R\right)$
 ${4}{}{{\mathrm{_A}}\left[\right]}^{{3}}{-}{16}{}{{\mathrm{_A}}}_{{y}{,}{y}}^{{2}}{}{{\mathrm{_A}}}_{{x}{,}{y}}{+}{16}{}{{\mathrm{_A}}}_{{x}{,}{y}}{}{{\mathrm{_A}}}_{{x}{,}{x}}^{{2}}{+}\left({-}{{x}}^{{2}}{-}{{y}}^{{2}}\right){}{{\mathrm{_A}}\left[\right]}^{{2}}{+}{16}{}{{\mathrm{_A}}}_{{y}{,}{y}}{}{{\mathrm{_A}}}_{{x}{,}{y}}{-}{16}{}{{\mathrm{_A}}}_{{x}{,}{y}}{}{{\mathrm{_A}}}_{{x}{,}{x}}$ (3)
 > $\mathrm{preparation_polynomial}\left(p,A\left[\right]=4u\left[\right]-{x}^{2}-{y}^{2},R\right)$
 ${{A}\left[\right]}^{{3}}{-}{4}{}{{A}}_{{y}{,}{y}}^{{2}}{}{{A}}_{{x}{,}{y}}{+}{4}{}{{A}}_{{x}{,}{y}}{}{{A}}_{{x}{,}{x}}^{{2}}{+}\left({2}{}{{x}}^{{2}}{+}{2}{}{{y}}^{{2}}\right){}{{A}\left[\right]}^{{2}}{+}\left({{x}}^{{4}}{+}{2}{}{{x}}^{{2}}{}{{y}}^{{2}}{+}{{y}}^{{4}}\right){}{A}\left[\right]$ (4)

Studying the degree in $A$ (or $\mathrm{_A}$) and its derivatives in these preparation polynomials, we can deduce that $u\left(x,y\right)=\frac{{x}^{2}}{4}+\frac{{y}^{2}}{4}$ is an essential singular zero of $p$ while $u\left(x,y\right)=0$ is not.

The preparation polynomial can be used to further study the relationships between the general zero and the singular zeros of $p$.

 > $R≔\mathrm{differential_ring}\left(\mathrm{ranking}=\left[y,A\right],\mathrm{derivations}=\left[x\right]\right):$
 > $p≔3{y\left[x\right]}^{4}y\left[\mathrm{}\left(x,2\right)\right]{y\left[\mathrm{}\left(x,4\right)\right]}^{2}-4{y\left[x\right]}^{4}{y\left[\mathrm{}\left(x,3\right)\right]}^{2}y\left[\mathrm{}\left(x,4\right)\right]+6{y\left[x\right]}^{3}{y\left[\mathrm{}\left(x,2\right)\right]}^{2}y\left[\mathrm{}\left(x,3\right)\right]y\left[\mathrm{}\left(x,4\right)\right]+24{y\left[x\right]}^{2}{y\left[\mathrm{}\left(x,2\right)\right]}^{4}y\left[\mathrm{}\left(x,4\right)\right]-12{y\left[x\right]}^{3}y\left[\mathrm{}\left(x,2\right)\right]{y\left[\mathrm{}\left(x,3\right)\right]}^{3}-29{y\left[x\right]}^{2}{y\left[\mathrm{}\left(x,2\right)\right]}^{3}{y\left[\mathrm{}\left(x,3\right)\right]}^{2}+12{y\left[\mathrm{}\left(x,2\right)\right]}^{7}$
 ${p}{≔}{3}{}{{y}}_{{x}}^{{4}}{}{{y}}_{{x}{,}{x}}{}{{y}}_{{x}{,}{x}{,}{x}{,}{x}}^{{2}}{-}{4}{}{{y}}_{{x}}^{{4}}{}{{y}}_{{x}{,}{x}{,}{x}}^{{2}}{}{{y}}_{{x}{,}{x}{,}{x}{,}{x}}{+}{6}{}{{y}}_{{x}}^{{3}}{}{{y}}_{{x}{,}{x}}^{{2}}{}{{y}}_{{x}{,}{x}{,}{x}}{}{{y}}_{{x}{,}{x}{,}{x}{,}{x}}{-}{12}{}{{y}}_{{x}}^{{3}}{}{{y}}_{{x}{,}{x}}{}{{y}}_{{x}{,}{x}{,}{x}}^{{3}}{+}{24}{}{{y}}_{{x}}^{{2}}{}{{y}}_{{x}{,}{x}}^{{4}}{}{{y}}_{{x}{,}{x}{,}{x}{,}{x}}{-}{29}{}{{y}}_{{x}}^{{2}}{}{{y}}_{{x}{,}{x}}^{{3}}{}{{y}}_{{x}{,}{x}{,}{x}}^{{2}}{+}{12}{}{{y}}_{{x}{,}{x}}^{{7}}$ (5)
 > $\mathrm{equations}\left(\mathrm{Rosenfeld_Groebner}\left(\left[p\right],R\right)\right)$
 $\left[\left[{3}{}{{y}}_{{x}}^{{4}}{}{{y}}_{{x}{,}{x}}{}{{y}}_{{x}{,}{x}{,}{x}{,}{x}}^{{2}}{-}{4}{}{{y}}_{{x}}^{{4}}{}{{y}}_{{x}{,}{x}{,}{x}}^{{2}}{}{{y}}_{{x}{,}{x}{,}{x}{,}{x}}{+}{6}{}{{y}}_{{x}}^{{3}}{}{{y}}_{{x}{,}{x}}^{{2}}{}{{y}}_{{x}{,}{x}{,}{x}}{}{{y}}_{{x}{,}{x}{,}{x}{,}{x}}{-}{12}{}{{y}}_{{x}}^{{3}}{}{{y}}_{{x}{,}{x}}{}{{y}}_{{x}{,}{x}{,}{x}}^{{3}}{+}{24}{}{{y}}_{{x}}^{{2}}{}{{y}}_{{x}{,}{x}}^{{4}}{}{{y}}_{{x}{,}{x}{,}{x}{,}{x}}{-}{29}{}{{y}}_{{x}}^{{2}}{}{{y}}_{{x}{,}{x}}^{{3}}{}{{y}}_{{x}{,}{x}{,}{x}}^{{2}}{+}{12}{}{{y}}_{{x}{,}{x}}^{{7}}\right]{,}\left[{{y}}_{{x}}^{{2}}{}{{y}}_{{x}{,}{x}{,}{x}}^{{2}}{+}{3}{}{{y}}_{{x}{,}{x}}^{{4}}\right]{,}\left[{{y}}_{{x}{,}{x}}\right]\right]$ (6)
 > $q≔3{y\left[x,x\right]}^{4}+{y\left[x\right]}^{2}{y\left[x,x,x\right]}^{2}$
 ${q}{≔}{{y}}_{{x}}^{{2}}{}{{y}}_{{x}{,}{x}{,}{x}}^{{2}}{+}{3}{}{{y}}_{{x}{,}{x}}^{{4}}$ (7)
 > $\mathrm{preparation_polynomial}\left(p,A\left[\right]=q,R\right)$
 $\left({-}{32}{}{{y}}_{{x}{,}{x}}{}{{y}}_{{x}{,}{x}{,}{x}}{}{{y}}_{{x}}{-}{32}{}{{y}}_{{x}{,}{x}}^{{3}}\right){}{{A}\left[\right]}^{{2}}{-}{8}{}{{y}}_{{x}}^{{2}}{}{{y}}_{{x}{,}{x}{,}{x}}{}{A}\left[\right]{}{{A}}_{{x}}{+}{3}{}{{y}}_{{x}{,}{x}}{}{{y}}_{{x}}^{{2}}{}{{A}}_{{x}}^{{2}}{+}\left({96}{}{{y}}_{{x}}{}{{y}}_{{x}{,}{x}}^{{5}}{}{{y}}_{{x}{,}{x}{,}{x}}{+}{96}{}{{y}}_{{x}{,}{x}}^{{7}}\right){}{A}\left[\right]$ (8)
 > $\mathrm{equations}\left(\mathrm{essential_components}\left(p,R\right)\right)$
 $\left[\left[{3}{}{{y}}_{{x}}^{{4}}{}{{y}}_{{x}{,}{x}}{}{{y}}_{{x}{,}{x}{,}{x}{,}{x}}^{{2}}{-}{4}{}{{y}}_{{x}}^{{4}}{}{{y}}_{{x}{,}{x}{,}{x}}^{{2}}{}{{y}}_{{x}{,}{x}{,}{x}{,}{x}}{+}{6}{}{{y}}_{{x}}^{{3}}{}{{y}}_{{x}{,}{x}}^{{2}}{}{{y}}_{{x}{,}{x}{,}{x}}{}{{y}}_{{x}{,}{x}{,}{x}{,}{x}}{-}{12}{}{{y}}_{{x}}^{{3}}{}{{y}}_{{x}{,}{x}}{}{{y}}_{{x}{,}{x}{,}{x}}^{{3}}{+}{24}{}{{y}}_{{x}}^{{2}}{}{{y}}_{{x}{,}{x}}^{{4}}{}{{y}}_{{x}{,}{x}{,}{x}{,}{x}}{-}{29}{}{{y}}_{{x}}^{{2}}{}{{y}}_{{x}{,}{x}}^{{3}}{}{{y}}_{{x}{,}{x}{,}{x}}^{{2}}{+}{12}{}{{y}}_{{x}{,}{x}}^{{7}}\right]{,}\left[{{y}}_{{x}}^{{2}}{}{{y}}_{{x}{,}{x}{,}{x}}^{{2}}{+}{3}{}{{y}}_{{x}{,}{x}}^{{4}}\right]\right]$ (9)

The general zero of $q$ is an essential singular zero of $p$ while the general zero of ${y}_{x,x}$ is not. Thus, the straight lines $y\left(x\right)=\mathrm{_C1}x+\mathrm{_C2}$, zeros of ${y}_{x,x}$, must be limits of either some non singular zeros of $p$ or of the non singular zeros of $q$. Again studying the degrees of the preparation polynomials of $p$ and $q$ we can deduce that the straight lines are in fact limits of the non singular zeros of both (cf. [Kolchin]).

 > $\mathrm{preparation_polynomial}\left(p,A\left[\right]=y\left[x,x\right],R\right)$
 ${12}{}{{A}\left[\right]}^{{7}}{+}{24}{}{{y}}_{{x}}^{{2}}{}{{A}\left[\right]}^{{4}}{}{{A}}_{{x}{,}{x}}{-}{29}{}{{y}}_{{x}}^{{2}}{}{{A}\left[\right]}^{{3}}{}{{A}}_{{x}}^{{2}}{+}{6}{}{{y}}_{{x}}^{{3}}{}{{A}\left[\right]}^{{2}}{}{{A}}_{{x}}{}{{A}}_{{x}{,}{x}}{-}{12}{}{{y}}_{{x}}^{{3}}{}{A}\left[\right]{}{{A}}_{{x}}^{{3}}{+}{3}{}{{y}}_{{x}}^{{4}}{}{A}\left[\right]{}{{A}}_{{x}{,}{x}}^{{2}}{-}{4}{}{{y}}_{{x}}^{{4}}{}{{A}}_{{x}}^{{2}}{}{{A}}_{{x}{,}{x}}$ (10)
 > $\mathrm{preparation_polynomial}\left(q,A\left[\right]=y\left[x,x\right],R\right)$
 ${3}{}{{A}\left[\right]}^{{4}}{+}{{y}}_{{x}}^{{2}}{}{{A}}_{{x}}^{{2}}$ (11)