## Tales from Wonderland

##### Original version

Tales from Wonderland by Ben David Normann. Stavanger : University of Stavanger, 2020 (PhD thesis UiS, no. 517)##### Abstract

Knowing that the Universe is quite isotropic, one may, as already discussed in Chapter 1, wonder how likely such a Universe is. We take the following research question.
Question 1. Is the asymptotic future of a cosmology filled with a perfect fluid alongside j-form matter isotropic?
Take a cosmological model (M, g, u). Then the research question stated above will be addressed under the following assumptions.
Assumption 5.1 (Philosophy). We assume the weak cosmological principle (WCP). Id est; we assume that the manifold M of the model is homogeneous on spatial sections, meanwhile simultaneously allowing for anisotropies in the metric g.
Assumption 5.2 (Matter). We take as matter content a perfect fluid with barotropic, non-phantom (a) equation of state with which the fundamental observer u will be aligned and a j-form fluid. We also investigate the effects of adding a cosmological constant.
Assumption 5.3 (Theory). General Relativity is assumed to be the correct theory of gravity.
Finally, in repetition: the ruthless swiftness of time has forced us to leave the Kantowski-Sachs model out and concentrate on the Bianchi models.
(a) With ‘barotropic’ we mean that the fluid is a function of pressure only. ‘Nonphantom’ means that the equation-of-state parameter Knowing that the Universe is quite isotropic, one may, as already discussed in Chapter 1, wonder how likely such a Universe is. We take the following research question.
Question 1. Is the asymptotic future of a cosmology filled with a perfect fluid alongside j-form matter isotropic?
Take a cosmological model (M, g, u). Then the research question stated above will be addressed under the following assumptions.
Assumption 5.1 (Philosophy). We assume the weak cosmological principle (WCP). Id est; we assume that the manifold M of the model is homogeneous on spatial sections, meanwhile simultaneously allowing for anisotropies in the metric g.
Assumption 5.2 (Matter). We take as matter content a perfect fluid with barotropic, non-phantom (a) equation of state with which the fundamental observer u will be aligned and a j-form fluid. We also investigate the effects of adding a cosmological constant.
Assumption 5.3 (Theory). General Relativity is assumed to be the correct theory of gravity.
Finally, in repetition: the ruthless swiftness of time has forced us to leave the Kantowski-Sachs model out and concentrate on the Bianchi models.
(a) With ‘barotropic’ we mean that the fluid is a function of pressure only. ‘Nonphantom’ means that the equation-of-state parameter y is not allowed to be negative.

##### Has parts

Paper 1: Normann B.D., Hervik S., Ricciardone A. and Thorsrud M. (2018) Bianchi cosmologies with p-form gauge ﬁelds, Classical and Quantum Gravity, 35(9). DOI: 10.1088/1361-6382/aab3a7. ArXiv:1712.08752v2 [gr-qc] (Preprint). Not available in Brage.Paper 2: Normann B.D., Hervik S., (2020) Approaching Wonderland. Classical and Quantum Gravity. 37(8), DOI: 10.1088/1361-6382/ab719b. ArXiv:1909.11962v2 [gr-qc]. (Preprint). Not available in Brage.

Paper 3: Paper 3: Normann B.D., Hervik S., Collins in Wonderland, Accepted for publication in Classical and Quantum Gravity. ArXiv:1910.12083v2 [gr-qc]. (Preprint). Not available in Brage.

Paper 4: Thorsrud M. and Normann B.D. and Pereira T. (2020) Extended FLRW Models: dynamical cancellation of cosmological anisotropies Classical and Quantum Gravity, 37(6). DOI: 10.1088/1361-6382/ab6f7f. ArXiv:1911.05793v2 [gr-qc] (Preprint). Not available in Brage.

Paper 5: Normann B.D. and Clarkson C. (2020) Recursion relations for gravitationalensing General Relativity and Gravitation, 52(3). DOI: 10.1007/s10714-020-02677-z. arXiv:1904.04471v2 [gr-qc] (Preprint). Not availble in Brage.