Some problems in constructing massive star models containing a chemically-inhomogeneous convective core with the local mixing-length theory

Some problems in constructing the massive star models which have a chemically-inhomogeneous convective core by using the local mixing-length theory are indicated. One problem is negative helium flux. Another one is a large discontinuity in velocity in the convective region. It does not seem easy to reconcile these problems with the present local mixing-length theory.