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Spectral analysis of one-dimensional Dirac operators with slowly decreasing potentials. (English) Zbl 1053.34075

Here, Dirac systems \(H(\alpha)\), \[ H(\alpha)u=\left(\begin{matrix} 0 & -1 \\ -1 & 0 \end{matrix} \right) u' + \left(\begin{matrix} p_1 & q \\ q & p_2 \end{matrix}\right)u \] on the half axis \((0,\infty)\) for a vector function \((u_1,u_2)^{ t}\) with the boundary condition \(u_1(0)\cos \alpha + u_2(0) \sin\alpha=0\) with square integrable potential, are studied. The author shows that the absolutely continuous spectrum of \(H(\alpha)\) covers the whole real line. For Coulomb-like potentials, it is shown that \(H(\alpha)\) has at most \(4C^2\) distinct eigenvalues, where \(C=\limsup_{x\to\infty} x | V(x)| \).

MSC:

34L05 General spectral theory of ordinary differential operators
34L40 Particular ordinary differential operators (Dirac, one-dimensional Schrödinger, etc.)
34B15 Nonlinear boundary value problems for ordinary differential equations
34B20 Weyl theory and its generalizations for ordinary differential equations
34L15 Eigenvalues, estimation of eigenvalues, upper and lower bounds of ordinary differential operators
47E05 General theory of ordinary differential operators
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