摘要:

AbstractProceedings of the Ninth Potsdam Seminar on Relativistic Astrophysics and Gravitation, held in Wusterhausen, GDR, 1989, October 23–

ISSN:0004-6337    

DOI:10.1002/asna.2113110302

出版商:WILEY‐VCH Verlag    

年代:1990

数据来源: WILEY

摘要:

AbstractWe consider general methods to find exact solutions of Kaluza‐Klein cosmologies with phenomenological matter and show some general conclusions about factorwise homogeneous and isotropic model

ISSN:0004-6337    

DOI:10.1002/asna.2113110303

出版商:WILEY‐VCH Verlag    

年代:1990

数据来源: WILEY

ISSN:0004-6337    

DOI:10.1002/asna.2113110304

出版商:WILEY‐VCH Verlag    

年代:1990

数据来源: WILEY

摘要:

AbstractWe 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 from the results of the quantum fluctuation analysis. The contraction of the internal scales produces effectively massive field modes in the ordinary space. The comparison of this particle creation with dark matter estimations informs us about the fundamental parameters of the mode

ISSN:0004-6337    

DOI:10.1002/asna.2113110305

出版商:WILEY‐VCH Verlag    

年代:1990

数据来源: WILEY

摘要:

AbstractReal‐time evolution plays an important role to understand the dynamics of the early Universe. It would be of importance to be able to investigate such typical time dependent processes like particle production, reheating, creation and evolution of fluctuations, etc. In this paper we derive the one‐loop renormalized coupled einstein field equations of a scalar field with λϕ4interaction in a classical curved space‐time of Friedmann‐Robertson‐Walker type. These equations can be used to calculate quantum corrections for the dynamics in the ear

ISSN:0004-6337    

DOI:10.1002/asna.2113110306

出版商:WILEY‐VCH Verlag    

年代:1990

数据来源: WILEY

摘要:

AbstractThe phase space of a cosmological model with a scalar field coupled to curvature is discussed in detail for any value of the coupling constant ξ and any power law (ϕ2n) potential. The results obtained generalize previous studies with minimal coupling (ξ = 0) and quadratic or quartic potentials to the entire parameter space (ξ,n). In many cases one finds global attractors and inflationary trajectories, with or without the correct Friedmannian limit. If the coupling constant is positive, a forbidden region cuts out a large part of the phase space, while, if it is negative, escaping regions may occur. Semi‐classical instability of vacuum states and singularity‐free trajectories are also di

ISSN:0004-6337    

DOI:10.1002/asna.2113110307

出版商:WILEY‐VCH Verlag    

年代:1990

数据来源: WILEY

摘要:

AbstractWe consider the spatially flat Friedmann model\documentclass{article}\pagestyle{empty}\begin{document}$$ \text{d}s^2 = \text{d}t^2 - a^2 (t)(\text{d}x^2 + \text{d}y^2 + \text{d}z^2). $$\end{document}Fora≈tp, especially, ifp≥ 1, this is called power‐law inflation. For the LagrangianL=Rmwithp= − (m− 1) (2m− 1)/(m− 2) power‐law inflation is an exact solution, as it is for Einstein gravity with a minimally coupled scalar field ϕ in an exponential potentialV(ϕ) = exp (μϕ) and also for the higher‐dimensional Einstein equation with a special Kaluza‐Klein ansatz. The synchronized coordinates are not adapted to allow a closed‐form solution, so we write\documentclass{article}\pagestyle{empty}\begin{document}$$ \text{d}s^2 = a^2 (Q^2 (a)\;\text{d}a^2 + \text{d}x^2 - \text{d}y^2 - \text{d}z^2). $$\end{document}The general solutions readsQ(a) = (ab+C)f/bwith free integration constantC(C= 0 gives exact power‐law inflation) andm‐dependent valuesbandf:f= −2 + 1/p, b= (4m− 5)/(m− 1). Finally, special solutions for the closed

ISSN:0004-6337    

DOI:10.1002/asna.2113110308

出版商:WILEY‐VCH Verlag    

年代:1990

数据来源: WILEY

摘要:

AbstractModels for the early Universe with the combined influence of scalar fields and vacuum polarization are discussed using phase plane portraints. The results concern the probability of the birth of the Universe, different de Sitter solutions and expressions for scalar perturbations.

ISSN:0004-6337    

DOI:10.1002/asna.2113110309

出版商:WILEY‐VCH Verlag    

年代:1990

数据来源: WILEY

摘要:

AbstractAU(1) model of gravitational, Higgs and, gauge fields is analysed. Two phases of the system are considered. In the case with broken symmetry we have the Nielsen‐Olesen configuration. In the symmetric phase we find a space‐time metricS2×E12. This appears in full analogy to the Freund‐Rubin compactification due to an antisymmeric tensor field. The connection of these structures with cosmic string phenomenology is an

ISSN:0004-6337    

DOI:10.1002/asna.2113110310

出版商:WILEY‐VCH Verlag    

年代:1990

数据来源: WILEY

ISSN:0004-6337    

DOI:10.1002/asna.2113110311

出版商:WILEY‐VCH Verlag    

年代:1990

数据来源: WILEY