Anistropic Invariant FRW Cosmology

In this paper we study the effects of including anisotropic scaling invariance in the minisuperspace Lagrangian for a universe modelled by the Friedman-Robertson-Walker metric, a massless scalar field and cosmological constant. We find that canonical quantization of this system leads to a Schroedinger type equation, thus avoiding the frozen time problem of the usual Wheeler-DeWitt equation. Furthermore, we find numerical solutions for the classical equations of motion, and we also find evidence that under some conditions the big bang singularity is avoided in this model.Comment: 6 pages, 5 figure

Black Hole Thermodynamics from a Noncommutative Area Operator

One key element to calculate thermodynamical properties for a black hole is the partition function. In this paper we have incorporated the idea of a two dimensional area in a noncommutative space and were able to calculate the partition function with such a spectra. Employing the canonical quantum statistics formalism we compute the temperature, entropy and time of evaporation for a Schwarzschild black hole.Comment: 4 pages, no figures, RevTex 4.

Deformed Phase Space Kaluza-Klein cosmology and late time acceleration

The effects of phase space deformations on Kalutza-Klein cosmology are studied. The deformation is introduced by modifying the symplectic structure of the minisuperspace variables. In the deformed model, we find an accelerating scale factor and therefore infer the existence of an effective cosmological constant from the phase space deformation parameter $\beta$.Comment: 5 pages, 2 figures, RevTeX 4.

Conformal Anisotropic Quantum Cosmology

In this paper we apply the ideas put forward by Ho\v{r}ava, and introduce anisotropic transformations to cosmology. We start with the Kantowski-Sachs cosmological model and impose anisotropic transformation invariance on the minisuperspace variables. We study the symmetries of the anisotropic model and by canonical quantization find a Schr\"odinger type equation for $z\ne 1$. Finally, we conclude that introducing anistropic invariance can be considered a solution to the problem of time in quantum cosmology and gives some insight on the structure of a well behaved quantum theory of gravity.Comment: 6 pages, no figures, RevTeX 4.

On Deformed Phase Space and Λ\Lambda

In this letter we study the effects of a noncommutative in the phase space of an empty (4+1) Kaluza-Klein universe with cosmological constant. We analyze the effects of the noncommutative deformations on the cosmological constant. Finally we comment on the possibility that the origin of the cosmological constant in this model, is related to the noncommutativity between the 4 dimensional scale factor and the compact extra dimension.Comment: 7 pages, no figures, JHEP styl

Classical and quantum Cosmology of the S\'aez-Ballester theory

We study the generalization of the S\'aez-Ballester theory applied to a flat FRW cosmological model. Classical exact solutions up to quadratures are easily obtained using the Hamilton-Jacobi approach. Contrary to claims in the specialized literature, it is shown that the S\'aez-Ballester theory cannot provide a realistic solution to the dark matter problem of Cosmology. Furthermore the quantization procedure of the theory can be simplified by reinterpreting the theory in the Einstein frame, where the scalar field can be interpreted as part of the matter content of the theory, in this approach, exact solutions are also found for the Wheeler-DeWitt equation in the quantum regime.Comment: 9 pages, late

Entropy using Path Integrals for Quantum Black Hole Models

Several eigenvalue equations that could describe quantum black holes have been proposed in the canonical quantum gravity approach. In this paper, we choose one of the simplest of these quantum equations to show how the usual Feynman's path integral method can be applied to obtain the corresponding statistical properties. We get a logarithmic correction to the Bekenstein-Hawking entropy as already obtained by other authors by other means.Comment: 7 pages, LaTeX, no figure

Effects of deformed phase space on scalar field cosmology

The effects of phase space deformations in standard scalar field cosmology are studied. The deformation is introduced by modifying the symplectic structure of the minisuperspace variables to have a deformed Poisson algebra among the coordinates and the canonical momenta. It is found that in the deformed minisuperspace model the volume of the universe is non singular. Finally, the late time evolution gives rise to an accelerating scale factor, this acceleration is a consequence of the noncommutative deformation.Comment: 4 pages, 1 figure, RevTeX 4.1, section 2 and 3 revised, result unchange

Phase space deformations in phantom cosmology

We discuss the physical consequences of making general phase space deformations on the minisuperspace of phantom cosmology. Based on the principle of physically equivalent descriptions in the deformed theory, we investigate for what values of the deformation parameters the arising descriptions are physically equivalent. We also construct and solve the quantum model and derive the semiclassical dynamics.Comment: 6 pages, 2 figures. v2: version to appear in Phys. Dark Uni

An Effective Cosmological Constant From an Entropic Formulation of Gravity

We use the ideas of entropic gravity to derive the FRW cosmological model and show that for late time evolution we have an effective cosmological constant. By using the first law of thermodynamics and the modified entropy area relationship derived from the supersymmetric Wheeler-DeWitt equation of the Schwarzschild black hole, we obtain modifications to the Friedmann equations that in the late time regime gives an effective positive cosmological constant. Therefore, this simple model can account for the dark energy component of the universe by providing an entropic origin to the cosmological constant $\Lambda$.Comment: 5 Pages, no figure