ASPECTS OF HEAVY-QUARK THEORY

Recent achievements in heavy-quark theory are critically reviewed. The emphasis is put on those aspects that either did not attract enough a ttention or cause heated debates in the current literature. Among othe r topics we discuss (a) basic parameters of the heavy-quark theory; (b ) a class of exact QCD inequalities; (c) new heavy quark sum rules; (d ) the virial theorem; (e) applications (\V-cb\ from the total semilept onic width and from the B --> D transition at zero recoil). In some i nstances new derivations of previously known results are given, or new aspects addressed. In particular, we dwell on the exact QCD inequalit ies. Furthermore, a toy model is considered that may shed light on the controversy regarding the value of the kinetic energy of heavy quarks obtained by different methods.