The one-dimensional Dirac operator with periodic potential
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844&_mathId=si2.gif&_user=111111111&_pii=S0022247X16305844&_rdoc=1&_issn=0022247X&md5=df14a243d399eb43f1480ff25ecccca2" title="Click to view the MathML source">P,Q∈L2([0,π]) subject to periodic, antiperiodic or a general strictly regular boundary condition (
bc ), has discrete spectrums. It is known that, for large enough
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n of radius 1/2, the operator has exactly two (periodic if
n is even or antiperiodic if
n is odd) eigenvalues
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