DYNAMICAL VACUUM IN QUANTUM COSMOLOGY

By regarding the vacuum as a perfect fluid with equation of state p = -rho, de Sitter's cosmological model is quantized. Our treatment diffe rs from previous ones in that it endows the vacuum with dynamical degr ees of freedom, following modern ideas that the cosmological term is a manifestation of the vacuum energy. Instead of being postulated from the start, the cosmological constant arises from the degrees of freedo m of the vacuum regarded as a dynamical entity, and a time variable ca n be naturally introduced. Taking the scale factor as the sole degree of freedom of the gravitational field, stationary and wave-packet solu tions to the Wheeler-DeWitt equation are found, whose properties are s tudied. It is found that states of the Universe with a definite value of the cosmological constant do not exist. For the wave packets invest igated, quantum effects are noticeable only for small values of the sc ale factor, a classical regime being attained at asymptotically large times.