193 research outputs found
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 .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 .
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
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
.Comment: 5 Pages, no figure
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