Motivated by recent studies of the one-bubble inflationary scenario, simple open cold dark matter models are tested for consistency with cosmological observations. The initial perturbation spectrum is derived by solving for the evolution of fluctuations in an open inflationary stage under the assumptions that a scalar field is in the Bunch-Davies vacuum state and the conformal vacuum state. A likelihood analysis is performed for the cosmic microwave background anisotropies using the two-year COBE Differential Microwave Radiometer (DMR) data. For Ωo ≲ 0.2, the two models give significantly different results because of the appearance of fluctuations of supercurvature scale in the model associated with the Bunch-Davies vacuum state. Having normalized the perturbation spectrum to fit the COBE data, we reconsider the validity of the open model from the viewpoint of cosmic structure formation. Open models may be severely constrained by the COBE likelihood analysis. In particular, small values of Ωo are ruled out in the Bunch-Davies case: we find that Ωo ≥ 0.34 at 95% confidence for this model.
All Science Journal Classification (ASJC) codes
- Astronomy and Astrophysics
- Space and Planetary Science