Bianchi type I, Schutz perfect fluid and evolutionary quantum cosmology

Abstract

We study the classical and quantum cosmology of a universe in which the matter content is a perfect fluid and the background geometry is described by a Bianchi type I metric. To write the Hamiltonian of the perfect fluid we use the Schutz representation, in terms of which, after a particular gauge fixing, we are led to an identification of a clock parameter which may play the role of time for the corresponding dynamical system. In view of the classical cosmology, it is shown that the evolution of the universe represents a late time expansion coming from a big-bang singularity. We also consider the issue of quantum cosmology in the framework of the canonical Wheeler-DeWitt (WDW) equation. It is shown that the Schutz formalism leads to the introduction of a momentum that enters linearly into Hamiltonian. This means that the WDW equation takes the form of a Schrödinger equation for the quantum-mechanical description of the model under consideration. We find the eigenfunctions and with the use of them construct the closed form expressions for the wave functions of the universe. By means of the resulting wave function we evaluate the expectation values and investigate the possibility of the avoidance of classical singularities due to quantum effects. We also look at the problem through Bohmian approach of quantum mechanics and while recovering the quantum solutions, we deal with the reason of the singularity avoidance by introducing quantum potential.

Noether Symmetry analysis in Chameleon Field Cosmology

“…In quantization of the model one has to construct the WD equation Ĥψ(u, v) = 0, with Ĥ the operator version of the Hamiltonian (50) and ψ(u, v), the wave function of the universe. In course of conversion to the operator version there is a problem related to the ordering of a variable and its conjugate momentum [48]. In the first term of the Hamiltonian (50) there is a product of 'a' and 'p a ', so one has to consider the ordering consideration: p a → −i∂ a , p φ → −i∂ φ .…”

Quantum cosmology with symmetry analysis for quintom dark energy model

“…However, there are some preferred choices for the triplets namely (i) l 1 = 2, m 1 = −1, n 1 = 0, l 2 = 2, m 2 = −1, n 2 = 0 which gives Laplace Beltrami operator and is known as D'Alembert operator ordering, (ii) l 1 = n 1 = 0, m 1 = 1, l 2 = n 2 = 0, m 2 = 1 is known as Vilenkin ordering, (iii) l 1 = 1, m 1 = n 1 = 0, l 2 = 1, m 2 = n 2 = 0, no ordering [47]. Note that though factor ordering affects the behaviour of the wave function, yet semi-classical calculations will be unaffected due to factor ordering [48].…”

Aspects of Quantum Cosmology

“…The present example is exactly that and this is one good reason for choosing Bianchi I at the outset. For a very brief review of various aspects of factor ordering, we refer to [98].…”