Kelvin functions

Kelvin functions, also known as cylindrical harmonics or modified Bessel functions of complex order, are special functions that arise in various problems in mathematical physics, particularly in wave propagation, heat conduction, and other areas where cylindrical symmetry is present. They are denoted as \( K_{\nu}(z) \) and \( I_{\nu}(z) \) for the Kelvin functions of the first kind and second kind, respectively.