Cyclical behavior in early universe cosmologies

This paper studies early universe cosmologies derived from a scalar-tensor action containing cosmological constant terms and massless fields. The gove rning equations can be written as a dynamical system which contains no past or future asymptotic equilibrium states (i.e., no sources nor sinks). This leads to dynamics with very interesting mathematical behavior such as the existence of heteroclinic cycles. The corresponding cosmologies have novel characteristics, including cyclical and bouncing behavior possibly indicati ng chaos. The connection between these early universe cosmologies and those derived from the low-energy string effective action is discussed. (C) 2000 American Institute of Physics. [S0022-2488(00)00709-X].