Nearly prime subsemigroups of ßN.
Noncompact semigroup actions.
Nonmetrizable topological dynamical characterization of central sets
Without the restriction of metrizability, topological dynamical systems are defined and uniform recurrence and proximality are studied. Some well known results are generalized and some new results are obtained. In particular, a topological dynamical characterization of central sets in an arbitrary semigroup (G,+) is given and shown to be equivalent to the usual algebraic characterization.
Nonreversibility of subsemigroups of semi-simple Lie groups.