Table 4 Eigenvalues of A in EHP algorithms

Jquad

$\begin{array}{l}{\lambda }_1=1\\ {\lambda }_{2,3}=\frac{6ma-2h^2\pm i\sqrt{36h^{2}ma-3h^4}}{6ma+h^2}\end{array}$

Uquad

$\begin{array}{l}{\lambda }_1=1\\ {\lambda }_{2,3}=\frac{6ma-2h^2\pm i\sqrt{36h^{2}ma-3h^4}}{6ma+h^2}\end{array}$

UJquad

$\begin{array}{l}{\lambda }_1=1\\ {\lambda }_{2,3}=\frac{h^4-60am{h}^2+144m^2{a}^2\pm i\left(12h\right)\left|12am-h^2\right|\sqrt{am}}{h^4+12am{h}^2+144m^2{a}^2}\end{array}$