Example: Constant astigmatism equation: Difference between revisions

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==Zero curvature representation==
==Zero curvature representation==


Let


<math>  
<math>  
A = \left(\begin{array}{cc}  
A = \left(\begin{array}{cc}  
\displaystyle \frac{1}{8} \frac{\lambda^2 + 1) z_x}{\lambda z} + \frac{1}{8} \frac{(-\lambda^2 + 1) z_y}{\lambda} &  
\displaystyle \frac{1}{8} \frac{(\lambda^2 + 1) z_x}{\lambda z} + \frac{1}{8} \frac{(-\lambda^2 + 1) z_y}{\lambda} &  
\displaystyle \frac{1}{4} \frac{(\lambda + 1)^2 \sqrt{z}}{\lambda} \\ \\
\displaystyle \frac{1}{4} \frac{(\lambda + 1)^2 \sqrt{z}}{\lambda} \\ \\
\displaystyle \frac{1}{4} \frac{(\lambda - 1)^2 \sqrt{z}}{\lambda} &  
\displaystyle \frac{1}{4} \frac{(\lambda - 1)^2 \sqrt{z}}{\lambda} &  
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\displaystyle \frac{1}{4} \frac{-\lambda^2 + 1}{\lambda \sqrt{z}} &  
\displaystyle \frac{1}{4} \frac{-\lambda^2 + 1}{\lambda \sqrt{z}} &  
\displaystyle -\frac{1}{8} \frac{(-\lambda^2 + 1) z_x}{\lambda z^2} - \frac{1}{8} \frac{(\lambda^2 + 1) z_y}{\lambda z}
\displaystyle -\frac{1}{8} \frac{(-\lambda^2 + 1) z_x}{\lambda z^2} - \frac{1}{8} \frac{(\lambda^2 + 1) z_y}{\lambda z}
  \end{array}\right)
  \end{array}\right).
</math>
</math>


[B-M]
Then <math>D_y - D_x + [A,B] = 0.</math> [B-M]





Revision as of 12:42, 6 December 2013

Equation

zyy+(1/z)xx+2=0.

[B-M]


Zero curvature representation

Let

A=(18(λ2+1)zxλz+18(λ2+1)zyλ14(λ+1)2zλ14(λ1)2zλ18(λ2+1)zxλz18(λ2+1)zyλ),

B=(18(λ2+1)zxλz2+18(λ2+1)zyλz14λ2+1λz14λ2+1λz18(λ2+1)zxλz218(λ2+1)zyλz).

Then DyDx+[A,B]=0. [B-M]


References

[B-M] H. Baran and M. Marvan, On integrability of Weingarten surfaces: a forgotten class, J. Phys. A: Math. Theor 42 (2009) 404007.