Failure of the collinear expansion in calculation of the induced gluon emission

We demonstrate that the collinear expansion fails in the case of gluon emission from a fast quark produced in $eA$ DIS. In this approximation the $N=1$ rescattering contribution to the gluon spectrum vanishes. We show that the higher-twist approach by Guo, Wang and Zhang [4, 5] based on the collinear expansion is wrong. The nonzero gluon spectrum obtained in [4, 5] those works is a consequence of an unjustified neglect of some important terms in the collinear expansion.