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32 Painlevé TranscendentsProperties

§32.9 Other Elementary Solutions

Contents
  1. §32.9(i) Third Painlevé Equation
  2. §32.9(ii) Fifth Painlevé Equation
  3. §32.9(iii) Sixth Painlevé Equation

§32.9(i) Third Painlevé Equation

Elementary nonrational solutions of \mbox{P}_{\mbox{\scriptsize III}} are

32.9.1 w(z;\mu,0,0,-\mu\kappa^{3})=\kappa z^{1/3},
32.9.2 w(z;0,-2\kappa,0,4\kappa\mu-\lambda^{2})=z(\kappa(\ln z)^{2}+\lambda\ln z+\mu),
32.9.3 w(z;-\nu^{2}\lambda,0,\nu^{2}(\lambda^{2}-4\kappa\mu),0)=\dfrac{z^{\nu-1}}{%
\kappa z^{2\nu}+\lambda z^{\nu}+\mu},

with \kappa, \lambda, \mu, and \nu arbitrary constants.

In the case \gamma=0 and \alpha\delta\neq 0 we assume, as in §32.2(ii), \alpha=1 and \delta=-1. Then \mbox{P}_{\mbox{\scriptsize III}} has algebraic solutions iff

32.9.4 \beta=2n,

with n\in\mathbb{Z}. These are rational solutions in \zeta=z^{1/3} of the form

32.9.5 w(z)=\ifrac{P_{n^{2}+1}(\zeta)}{Q_{n^{2}}(\zeta)},

where P_{n^{2}+1}(\zeta) and Q_{n^{2}}(\zeta) are polynomials of degrees n^{2}+1 and n^{2}, respectively, with no common zeros. For examples and plots see Clarkson (2003a) and Milne et al. (1997). Similar results hold when \delta=0 and \beta\gamma\neq 0.

\mbox{P}_{\mbox{\scriptsize III}} with \beta=\delta=0 has a first integral

32.9.6 z^{2}(w^{\prime})^{2}+2zww^{\prime}=(C+2\alpha zw+\gamma z^{2}w^{2})w^{2},

with C an arbitrary constant, which is solvable by quadrature. A similar result holds when \alpha=\gamma=0. \mbox{P}_{\mbox{\scriptsize III}} with \alpha=\beta=\gamma=\delta=0, has the general solution w(z)=Cz^{\mu}, with C and \mu arbitrary constants.

§32.9(ii) Fifth Painlevé Equation

Elementary nonrational solutions of \mbox{P}_{\mbox{\scriptsize V}} are

32.9.7 w(z;\mu,-\tfrac{1}{8},-\mu\kappa^{2},0)=1+\kappa z^{1/2},
32.9.8 w(z;0,0,\mu,-\tfrac{1}{2}\mu^{2})=\kappa\exp\left(\mu z\right),

with \kappa and \mu arbitrary constants.

\mbox{P}_{\mbox{\scriptsize V}}, with \delta=0, has algebraic solutions if either

32.9.9 \mspace{17.0mu}(\alpha,\beta,\gamma)=(\tfrac{1}{2}\mu^{2},-\tfrac{1}{8}(2n-1)^%
{2},-1),

or

32.9.10 \mspace{5.0mu}(\alpha,\beta,\gamma)=(\tfrac{1}{8}(2n-1)^{2},-\tfrac{1}{2}\mu^{%
2},1),

with n\in\mathbb{Z} and \mu arbitrary. These are rational solutions in \zeta=z^{1/2} of the form

32.9.11 w(z)=\ifrac{P_{n^{2}-n+1}(\zeta)}{Q_{n^{2}-n}(\zeta)},

where P_{n^{2}-n+1}(\zeta) and Q_{n^{2}-n}(\zeta) are polynomials of degrees n^{2}-n+1 and n^{2}-n, respectively, with no common zeros.

\mbox{P}_{\mbox{\scriptsize V}}, with \gamma=\delta=0, has a first integral

32.9.12 z^{2}(w^{\prime})^{2}=(w-1)^{2}(2\alpha w^{2}+Cw-2\beta),

with C an arbitrary constant, which is solvable by quadrature. For examples and plots see Clarkson (2005). \mbox{P}_{\mbox{\scriptsize V}}, with \alpha=\beta=0 and \gamma^{2}+2\delta=0, has solutions w(z)=C\exp\left(\pm\sqrt{-2\delta}z\right), with C an arbitrary constant.

§32.9(iii) Sixth Painlevé Equation

An elementary algebraic solution of \mbox{P}_{\mbox{\scriptsize VI}} is

32.9.13 w(z;\tfrac{1}{2}\kappa^{2},-\tfrac{1}{2}\kappa^{2},\tfrac{1}{2}\mu^{2},\tfrac{%
1}{2}(1-\mu^{2}))=z^{1/2},

with \kappa and \mu arbitrary constants.

Dubrovin and Mazzocco (2000) classifies all algebraic solutions for the special case of \mbox{P}_{\mbox{\scriptsize VI}} with \beta=\gamma=0, \delta=\tfrac{1}{2}. For further examples of algebraic solutions see Andreev and Kitaev (2002), Boalch (2005, 2006), Gromak et al. (2002, §48), Hitchin (2003), Masuda (2003), and Mazzocco (2001b).