• D. Lorenz-Petzold

      Articles written in Journal of Astrophysics and Astronomy

    • Higher-dimensional bianchi type-VIh cosmologies

      D. Lorenz-Petzold

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      We present the higher-dimensional perfect fluid generalizations of the extended Bianchi type-VIh vacuum space-times discussed recently by Demaret & Hanquin (1985). It is shown that the Chodos-Detweiler mechanism of cosmological dimensional-reduction is possible in these cases.

    • Higher-dimensional vacuum bianchi-mixmaster cosmologies

      D. Lorenz-Petzold

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      We derive some new exact 7-dimensional cosmological solutions |R⊗ I ⊗N, whereN = I, II, VI0, VII0, VIII and IX are the various 3-dimensional Bianchi models. The solutions given are higher-dimensional generalizations of the mixmaster cosmologies. There is a strong influence of the extra spacesN, which results in a fundamental change of the 3-dimensional cosmology.

    • Is the Stephani-Krasiński solution a viable model of the Universe?

      D. Lorenz-Petzold

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      We present a detailed study of the inhomogeneous Stephani-Krasinski solution with time-dependent curvature index. In general, the cosmological behaviour of the models depends on six arbitrary functions of time. Such models are termed ‘private universes’ and cannot be in accord with observation in the most general case. Two simple models with changing topology are considered as illustrating examples. In one of these models the pressure turns out to be negative and hence a violation of the weak energy condition in the singularity theorems is possible. A brief review of other inhomogeneous cosmologies is included for the sake of clarity. It is shown that the geodesic equation can be reduced to a complicated differential equation, which depends on the three arbitrary functions involved. Therefore, it is difficult to obtain explicit formulas for the various observational relations.

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    • Continuous Article Publication

      Posted on January 27, 2016

      Since January 2016, the Journal of Astrophysics and Astronomy has moved to Continuous Article Publishing (CAP) mode. This means that each accepted article is being published immediately online with DOI and article citation ID with starting page number 1. Articles are also visible in Web of Science immediately. All these have helped shorten the publication time and have improved the visibility of the articles.

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