Kaluza-Klein Cosmological Model Research Articles

Extra force and extra mass from non-compact Kaluza-Klein theory in a cosmological model

Using the Hamilton-Jacobi formalism, we study extra force and extra mass in a recently introduced non-compact Kaluza-Klein cosmological model. We examine the inertial 4D mass m0 of the inflaton field on a 4D FRW bulk in two examples. We find that m0 has a geometrical origin and antigravitational effects on a non-inertial 4D bulk should be a consequence of the motion of the fifth coordinate with respect to the 4D bulk.

HIGHER DIMENSIONAL COSMOLOGICAL MODEL IN LYRA GEOMETRY: REVISITED

In this paper we have revisited the research work of Rahman and Bera22on Kaluza–Klein cosmological model within the framework of Lyra Geometry. It has been shown that the empty universe model yields a power law relation without any assumption. The role of bulk viscosity on five-dimensional cosmological model is discussed. The physical behaviour of the models is examined in all cases.

HIGHER DIMENSIONAL COSMOLOGICAL MODEL IN LYRA GEOMETRY

In this paper Kaluza–Klein cosmological model within the framework of Lyra geometry has been discussed. The physical behavior of the model is examined in vacuum and in the presence of perfect fluids.

Compactification of extra dimensions in quantum inhomogeneous Kaluza-Klein cosmological models

Quantum dynamics of inhomogeneous Kaluza-Klein cosmological models in the vicinity of a cosmological singularity is considered. It is shown that in the early universe if the number of dimensions D is less than or equal to ten, mean values of the metric indicate the existence of the initial stage of a compactification process. It is shown that such a behaviour of the mean values does not depend on a particular choice of an initial quantum state and, therefore, is a general property of the quantum evolution in the inhomogeneous Kaluza-Klein cosmologies.

On properties of metrics inhomogeneities in the vicinity of a singularity in Kaluza-Klein cosmological models

Abstract We discuss the dynamics of inhomogeneities of metric in a general solution to D-dimensional Einstein equation with matter sources satisfying the inequality ∊ ≥ p in the vicinity of a cosmological singularity. It is shown that a local behavior of a part of metric functions near the singularity is described by a billiard on a space of a constant negative curvature. If D ≤ 10, the billiard has a finite volume and, consequently, it is a mixing one. It is shown for this case that statistical properties of inhomogeneities of metric admit a complete description. An invariant measure describing statistics of inhomogeneities is obtained and the role of a minimally-coupled scalar field in the dynamics of the inhomogeneities is also considered.

Quantum Kaluza-Klein cosmology in the Vilenkin theory

In this paper, we discuss the quantum Kaluza-Klein cosmological model in the Vilenkin theory, and give the corresponding tunnelling wave function.

Solution of dirac equation in a singularity-free Kaluza-Klein cosmological model

The singularity-free solution of (4 + D) -dimensional Einstein field equations for the Kaluza-Klein cosmological model is obtained. Then the Dirac equations are solved in this model.

The boost-like symmetry of Kaluza-Klein cosmologies

For a large class of toroidally compact, spacially flat Kaluza-Klein cosmological models, we display the existence of an additional dynamical symmetry. The corresponding conserved quantity F, is related to the anisotropy in the evolution of the Universe. In the context of the third quantized mini-superspace Wheeler-De Witt equation, for some of these models, we analyze the spontaneous creation of anisotropic universes from “nothing” with a resulting thermal distribution in the possible eigenvalues of F.

D-dimensional torus as compact manifold and Kaluza–Klein cosmological model

Singularity-free solutions of higher-dimensional Einstein field equations are obtained in the background of M4×TD manifold (M4 is a usual four-dimensional Friedmann– Robertson–Walker model and TD is a D-dimensional torus). Moreover, through dimensional reduction and one-loop quantum correction to scalar field, time-dependent cosmological constant Λ, effective gravitational constant Geff, and a fine-structure constant e/4π are derived in the effective four-dimensional theory using solutions of Einstein’s equations. It is found that at late times Λ≂0.

Inflationary solution in higher dimensions

In this Letter the five-dimensional Kaluza-Klein cosmological model is studied in the presence of a massless scalar field, whose potential has a flat part. By use of the polynomial relation between the two scale factors, inflationary solutions are obtained. The results show that the scale factor corresponding to the extra dimension is either constant or varies inversely as some power of the usual scale factor.

Bulk viscosity, Kaluza-Klein models and inflation

In this work we have employed two hypotheses which have been separately used in order to try to solve the horizon problem, the first one is to take a Kaluza-Klein cosmological model withd noncompact andD compact space-like dimensions, in particular we considerD=1, the second one is to use an energy-momentum tensor depicting a fluid out of equilibrium, in particular we take a mixture of two gases, one is formed by relativistic particles and the other one is a gas constituted by non-relativistic particles and they are not in thermodynamical equilibrium, such that a bulk viscosity term arises. Without actually solving the Einstein equations, we prove that the scale factor of the non-compact space is a monotonic increasing function of time, and that if the scale factor of the compact space reaches a maximum at a certain time then the non-compact space is driven to expand rapidly, and, therefore, hinting us about the possibility of solving the horizon problem.

Some more methods and exact solutions to solve Kaluza-Klein cosmologies

The authors consider general methods to solve the equations for Kaluza-Klein cosmological models by using the formal identity of these equations with those of a relativistic point particle in a scalar field. The formal scalar field is given by the phenomenological matter content of the cosmological model in dependence of the difference expansion factors. They find general solutions for one- and two-component matter and general properties of such models.

Mixed metric perturbations in Kaluza-Klein cosmologies

We consider metric perturbations of Kaluza-Klein cosmological models filled with phenomenological matter. We find the exact solution for the development in time of the mixed perturbations, which have one index in the ordinary and one in the internal space. The initial values are assumed to be taken as quantum fluctuation. The contraction of the internal scales produces effectively massive wave modes in the ordinary space. The comparison of this particle creation with dark-matter estimations informs us about the fundamental parameters of the model.

Kaluza-Klein cosmology withN dilaton fields

The ground state for Kaluza-Klein cosmological models with more than one dilaton field is considered. The dimensional reduction is performed and the equations of motion for the dilaton fields are considered. The normal modes of oscillation are found, one of them,ψ, being the conformai factor in front of the metric for the true four-dimensional space-time. It is shown that a stable minimum exists when both the cosmological term and all the scalar curvatures of the extra-dimensional subspaces are negative. If all these scalar curvatures are positive, the extra-dimensional subspaces collapse and the quantum effects should be taken into account to stabilize them. All other combinations of the signs of scalar curvatures lead to decompactification of some of the subspaces. Some cosmological applications are discussed. One of them concerns the possibility of constructing Big-Bang cosmological models starting from a nonsingular higher-dimensional space-time.

Quantum Kaluza-Klein cosmologies (IV)

The density matrix of a five-dimensional Kaluza-Klein cosmological model is presented. The entropy of this toy model is discussed.

The fate of the mixmaster behaviour in vacuum inhomogeneous Kaluza-Klein cosmological models

The generic behaviour of vacuum inhomogeneous Kaluza-Klein cosmologies is studied in the vicinity of the cosmological singularity. The collision law for the Kasner exponents is calculated in any number of spatial dimensions d. Its properties are investigated both theoretically and numerically. It is argued that the chaotic oscillatory behaviour disappears for d ⩾ 10. This regime is replaced by the monotonic Kasner behaviour found previously.

The stability of some Kaluza-Klein cosmological models

The stability is examined of some exact Kaluza-Klein cosmological solutions that possess static extra dimensions and standard Friedman behaviour for the remaining three spatial dimensions. It is shown that even when the extra dimensions are asymptotically static they produce a deviation from Friedman behaviour in the observable three spatial dimensions. A similar effect is found for models with anisotropically expanding three-spaces.

Cosmology in D-dimensional gravity coupled to a rank-three field FMNP

We have shown that spontaneous compactification in D-dimensional gravity coupled to a rank-three field F MNP leads to a product of a four-spacetime and an extra-( D − 4) internal space for the Kaluza-Klein cosmological model. In this model we obtain that for the early universe with negligible k 3( k r ) the three spatial dimensions evolve exponentially, while the internal manifold with constant magnitude oscillates in time. We also find that both the extra-dimensions and the gauge field F MNP play crucial roles in the exponentially expanding universe.

Temperature effects in five-dimensional Kaluza-Klein theory

We examine the combined effectsof thermal and quantum-mechanical fluctuations in a Kaluza-Klein universe with a single compact spatial dimension of length L¯5. From the one-loop effective potential for L¯5 two types of instability are evident. If initially L¯5 is less than a temperature-dependent critical length, L¯5 will shrink at least down to a length comparable to the Planck length. This instability has been noted by Appelquist and Chodos in the zero-temperature limit. If, on the other hand, L¯5 starts out larger than the critical length, it will tend to increase. This result suggests that temperature effects may play an important role in Kaluza-Klein cosmological models.