An orthogonal net on a surface in Euclidean -space in which the small quadrangles formed by two pairs of lines from distinct families are, up to infinitesimal quantities of the first order, squares. The lines of an isothermal net are level curves of two conjugate harmonic functions. In the parameters of an isothermal net the line element has the form:
See also Isothermal coordinates and the references given there.
Isothermal net. Encyclopedia of Mathematics. URL: http://encyclopediaofmath.org/index.php?title=Isothermal_net&oldid=13253