Artificial Singularity in theNDEquations of the New Strip Approximation

The singularity introduced artificially into the equations of the new strip approximation, in order to bridge the gap between low and high energies, is investigated in detail. By explicit construction, it is shown that a necessary and sufficient condition for a (unique) solution of the $\frac{N}{D}$ equations to exist is that the unitarity constraint on the cross section just above the strip boundary should be obeyed. The only singularities of the solution in the right-half angular momentum plane ($\mathrm{Re}J\ge 0$) are Regge poles.