Accelerated expansion in bosonic and fermionic 2D cosmologies with quantum effectsL. L. Samojeden, G. M. Kremer and F. P. Devecchi
Departamento de Física, Universidade Federal do Paraná - Caixa Postal 19044, 81531-990, Curitiba, Brazil
received 5 March 2009; accepted in final form 15 June 2009; published July 2009
published online 15 July 2009
In this work we analyze the effects produced by bosonic and fermionic constituents, including quantum corrections, in two-dimensional (2D) cosmological models. We focus on a gravitational theory related to the Callan-Giddings-Harvey-Strominger model, to simulate the dynamics of a young, spatially lineal, universe. The cosmic substratum is formed by an inflaton field plus a matter component, sources of the 2D gravitational field; the degrees of freedom also include the presence of a dilaton field. We show that this combination permits, among other scenarios, the simulation of a period of inflation, that would be followed by a (bosonic/fermionic)-matter-dominated era. We also analyse how quantum effects contribute to the destiny of the expansion, given the fact that in 2D we have a consistent (renormalizable) quantum theory of gravity. The dynamical behavior of the system follows from the solution of the gravitational-field equations, the (Klein-Gordon and Dirac) equations for the sources and the dilaton-field equation. Consistent (accelerated) regimes are present among the solutions of the 2D equations; the results depend strongly on the initial conditions used for the dilaton field. In the particular case where fermions are included as matter fields a transition to a decelerated expansion is possible, something that does not happen in the exclusively bosonic case.
04.60.Kz - Lower dimensional models; minisuperspace models.
98.80.-k - Cosmology.
98.80.Cq - Particle-theory and field-theory models of the early Universe (including cosmic pancakes, cosmic strings, chaotic phenomena, inflationary universe, etc.).
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