Quintom potentials from a quantum anisotropic model (original) (raw)
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Troubles with Quantum Anisotropic Cosmological Models: Loss of Unitarity
General Relativity and Gravitation, 2003
The anisotropic Bianchi I cosmological model coupled with perfect fluid is quantized in the minisuperspace. The perfect fluid is described by using the Schutz formalism which allows to attribute dynamical degrees of freedom to matter. A Schrödinger-type equation is obtained where the matter variables play the role of time. However, the signature of the kinetic term is hyperbolic. This Schrödingerlike equation is solved and a wave packet is constructed. The norm of the resulting wave function comes out to be time dependent, indicating the loss of unitarity in this model. The loss of unitarity is due to the fact that the effective Hamiltonian is hermitian but not self-adjoint. The expectation value and the bohmian trajectories are evaluated leading to different cosmological scenarios, what is a consequence of the absence of a unitary quantum structure. The consistency of this quantum model is discussed as well as the generality of the absence of unitarity in anisotropic quantum models.
Quintom Potentials from Quantum Cosmology Using the FRW Cosmological Model
International Journal of Theoretical Physics, 2013
We construct the quintom potential of dark energy models in the framework of spatially flat Friedmann-Robertson Walker universe in the inflationary epoch, using the Bohm like approach, known as amplitude-real-phase. We find some potentials for which the wave function of the universe is found analytically and we have obtained the classical trajectories in the inflation era.
Quantum Potential Approach to Class of Cosmological Models
1995
In this paper we discuss the quantum potential approach of Bohm in the context of quantum cosmological model. This approach makes it possible to convert the wavefunction of the universe to a set of equations describing the time evolution of the universe. Following Ashtekar et.\ al., we make use of quantum canonical transformation to cast a class of quantum cosmological models to a simple form in which they can be solved explicitly, and then we use the solutions do recover the time evolution.
Quantum potential approach to a class of quantum cosmological models
Classical and Quantum Gravity, 1996
In this paper we discuss the quantum potential approach of Bohm in the context of a quantum cosmological model. This approach makes it possible to convert the wavefunction of the universe into a set of equations describing the time evolution of the universe. Following Ashtekar et al we make use of a quantum canonical transformation to cast a class of a quantum cosmological models into a simple form in which they can be solved explicitly, and then we use the solutions to recover the time evolution.
Cosmology from quantum potential
Physics Letters B, 2015
It was shown recently that replacing classical geodesics with quantal (Bohmian) trajectories gives rise to a quantum corrected Raychaudhuri equation (QRE). In this article we derive the second order Friedmann equations from the QRE, and show that this also contains a couple of quantum correction terms, the first of which can be interpreted as cosmological constant (and gives a correct estimate of its observed value), while the second as a radiation term in the early universe, which gets rid of the big-bang singularity and predicts an infinite age of our universe.
Accelerating dark energy models with anisotropic fluid in Bianchi type VI 0 space-time
Research in Astronomy and Astrophysics, 2013
Motivated by the increasing evidence for the need of a geometry that resembles Bianchi morphology to explain the observed anisotropy in the WMAP data, we have discussed some features of Bianchi type VI 0 universes in the presence of a fluid that has an anisotropic equation of state (EoS) parameter in general relativity. We present two accelerating dark energy (DE) models with an anisotropic fluid in Bianchi type VI 0 space-time. To ensure a deterministic solution, we choose the scale factor a(t) = √ t n e t , which yields a time-dependent deceleration parameter, representing a class of models which generate a transition of the universe from the early decelerating phase to the recent accelerating phase. Under suitable conditions, the anisotropic models approach an isotropic scenario. The EoS for DE ω is found to be time-dependent and its existing range for derived models is in good agreement with data from recent observations of type Ia supernovae (SNe Ia) , SNe Ia data combined with cosmic microwave background (CMB) anisotropy and galaxy clustering statistics , as well as the latest combination of cosmological datasets coming from CMB anisotropies, luminosity distances of high redshift SNe Ia and galaxy clustering. For different values of n, we can generate a class of physically viable DE models. The cosmological constant Λ is found to be a positive decreasing function of time and it approaches a small positive value at late time (i.e. the present epoch), which is corroborated by results from recent SN Ia observations. We also observe that our solutions are stable. The physical and geometric aspects of both models are also discussed in detail.
Quantum potential approach to quantum cosmology
1995
In this paper we discuss the quantum potential approach of Bohm in the context of quantum cosmological model. This approach makes it possible to convert the wavefunction of the universe to a set of equations describing the time evolution of the universe. Following Ashtekar et. al., we make use of quantum canonical transformation to cast a class of quantum cosmological models to a simple form in which they can be solved explicitly, and then we use the solutions do recover the time evolution.
Bianchi type-I cosmological models with time dependent q and Λ-term in general relativity
Astrophysics and Space Science, 2013
On getting motivation from increasing evidence for the need of a geometry that resembles Bianchi morphology to explain the observed anisotropy in the WMAP data, Einstein's field equations with variable cosmological "constant" are considered in presence of perfect fluid for a homogeneous and anisotropic Bianchi type-I space-time. Einstein's field equations are solved by considering a time dependent deceleration parameter which affords a late time acceleration in the universe. The cosmological constant Λ is found to be a decreasing function of time and it approaches a small positive value at the present epoch which is corroborated by consequences from recent supernovae Ia observations. From recently developed Statefinder pair, the behavior of different stages of the evolution of the universe has been studied. The physical significance of the cosmological models have also been discussed.
2017
In this work the scalar free Klein-Gordon field coupled to the quantum mechanical gravity equation (QMGE), that takes into account the quantum property of matter, is quantized. The model has been developed at the first order in the metric tensor with a self-consistent analytical dependence of the energy impulse tensor by the quantum field. The quantum behavior, due to the quantum potential energy, in the gravity equation (GE) has been investigated by studying the energy-impulse tensor density generated the quantum field. The outputs of the theory show that the vacuum energy density of the zero point is effective for the cosmological constant only in the volume of space where the mass is localized in particles or in high gravity bodies, leading to a cosmological effect on the motion of the galaxies that is compatible with the astronomical observations. The paper shows that the energy-impulse tensor density makes the QMGE, in the quasi-Euclidean limit, physically independent by the le...