QUALITATIVE-ANALYSIS OF DIAGONAL BIANCHI TYPE-V IMPERFECT FLUID COSMOLOGICAL MODELS

The Einstein field equations for diagonal Bianchi type V imperfect flu id cosmological models with both viscosity and heat conduction are set up as an autonomous system of differential equations using dimensionl ess variables and a set of dimensionless equations of state. Models wi th and without a cosmological constant, lambda, are investigated using the techniques from dynamical systems theory. It is shown that all mo dels that satisfy the weak energy conditions isotropize. The introduct ion of viscosity (in particular) allows for a variety of different qua litative behaviors (including, for example, models with a negative dec eleration parameter). Exact solutions that correspond to the singular points of the dynamical system are found. It is shown that the past as ymptotic states are represented by self-similar cosmological models an d, if lambda = 0, the future asymptotic states are also, in general, r epresented by self-similar cosmological models; in the exceptional cas es the late time asymptotic state is represented by a de Sitter model with constant expansion, as is the case for solutions with lambda not- equal 0.