An Extension of Lie's Theorem on Isothermal Families.
نویسندگان
چکیده
where E(x, y) > 0. The parametric curves x = const. and y = const. form an isothermal net on 1. It is well known that h(x, y) = c, where h is a harmonic function of (x, y), that is, h satisfies the Laplace equation, hA, + h,, = 0, defines an isothermal family of curves on Z. The constant c is called the isothermal parameter. The converse of the preceding statement is not valid. That is, if g(x, y) = const. defines an isothermal family of curves on 2 with linear-element of the form (1), then it does not follow necessarily that g is a harmonic function, but it must be a function of a harmonic function. The exact statement which is due to Lie is as follows. The family of curves g(x, y) = const. represents an isothermal system on the surface 2 with linear-element of the form (1), if and only if g satisfies the partial differential equation of third order
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ورودعنوان ژورنال:
- Proceedings of the National Academy of Sciences of the United States of America
دوره 31 1 شماره
صفحات -
تاریخ انتشار 1945