Fig. 4From: Orthogonality, Lommel integrals and cross product zeros of linear combinations of Bessel functionsExact numerical solution of the first eigenvalue \(\lambda _{1,\nu }\) of Eq. (76) for \(\nu =2\) (shown in the black solid line) and comparison with approximate solutions [red solid line from Eq. (87) and blue solid line from Eq. (89)) and results from Grebenkov (green solid line obtained from Eq. (91)] and Gottlieb [green dashed line obtained from Eq. (91)].Back to article page