On the asymptotic expansion of the characteristic determinant for a \(2 \times 2\) Dirac type system (Q6634787)

In this paper the authors consider the equation\N\[\NiB^{-1} y'+Q(x) y=\lambda y\N\]\Nwhere \(Q\in W_1^n [0,1]\otimes \mathbb{C}^{2\times 2}\) is a smooth matrix function,\N\(B=\begin{pmatrix} b_1 & 0 \\ 0 & b_2\end{pmatrix}\), \(y=(y_1, y_2)\), \(b_1 < 0 < b_2\).\N\NThe authors introduce the asymptotic expansion of the characteristic determinant of the corresponding boundary value problem.