MF-traces and a Lower Bound for the Topological Free Entropy Dimension in Unital C*-algebras

We continue previous work on Voiculescu's topological free entropy dimension δ_{top}. We introduce the notions of MF-trace, MF-ideal, and MF-nuclearity and use these concepts to obtain upper and lower bounds for δ_{top}, and in many cases we obtain an exact formula for δ_{top}. We also discuss semicontinuity properties of δ_{top}.