Modified Bessel functions: , The Bessel functions are valid even for complex arguments , and an important special case is that of a purely imaginary argument. In this case, the solutions to the Bessel equation are called the modified Bessel functions (or occasionally the hyperbolic Bessel functions) of the first and second kind and are defined asAbramowitz and Stegun, p. 375, 9.6.2, 9.6.10, 9.6.11.
Modified Bessel functions: , The Bessel functions are valid even for complex arguments , and an important special case is that of a purely imaginary argument. In this. case, the solutions to the Besse?l equation are called t.he modified Bessel functions (or occasionally the hyperbolic Bessel functions) of the first and second kind and are defined asAbramowitz and Stegun, p. 375, 9.6.2, 9.6.10, 9.6.11.