Periodic Reporting for period 3 - ARTHUS (Advances in Research on Theories of the Dark Universe - Inhomogeneity Effects in Relativistic Cosmology)
Berichtszeitraum: 2020-09-01 bis 2022-02-28
For Axis B, we developed statistical tools complementary to the Minkowski functionals. Six publications resulted, [ https://arxiv.org/abs/1812.07310 ], a discovery of a new anomaly [ https://arxiv.org/abs/1812.07678 ], and [ https://arxiv.org/abs/1908.01619 ], [ https://arxiv.org/abs/2011.12851 ], [ https://arxiv.org/abs/2109.08721 ], and a follow-up of the application to the detected new CMB anomaly [ https://arxiv.org/abs/2111.15427 ], driven by Pratyush Pranav. The PI is member of and has communicated observational predictions for the forthcoming surveys Euclid and 4MOST; for 4MOST see [ https://arxiv.org/abs/1903.02474 ]. Martin France and team members have proposed a new statistics to detect whether or not the Universe has finite volume
[ https://arxiv.org/abs/2106.13205 ]. For the application to galaxy catalog data: [ https://arxiv.org/abs/2110.06109 ].
For Axis C, we concentrated on closure conditions of the averaged equations using topological constraints [ https://arxiv.org/abs/2002.08336 ].
We could answer two criticisms, namely (i) the dependence on this foliation choice and (ii) the covariance of the averaged equations. To (i): the Letter [ https://arxiv.org/abs/1805.10455 ] provides an astonishingly simple answer. It is based on a large paper as `Editor's Choice Research Article' [ https://arxiv.org/abs/1912.04213 ]. To (ii): the covariance is built into the scheme [ https://arxiv.org/abs/1811.01374 ]. We attacked the high-risk WP of averaging on the light cone, finalized in [ https://arxiv.org/abs/2202.10798 ]. Asta Heinesen started a general model-independent strategy and has substantially advanced this line of research, and accomplished this goal locally: [ https://arxiv.org/abs/2011.10048 ], [ https://arxiv.org/abs/2102.03774 ],
[ https://arxiv.org/abs/2010.06534 ].
A further key-question of ARTHUS could be substantially advanced. We succeeded, along a 'high-risk route', to obtain a unique further equation that governs the evolution of those 'backreaction terms' that potentially replace the dark components in the standard model of cosmology. This route went deep into the mathematical discipline of topology pursued with the mathematician Léo Brunswic (ERC postdoc) [ https://arxiv.org/abs/2002.08336 ]. With these results we also found two links to results of Axis A. While closure is not achieved yet, these results form a significant (and unexpected) step forward to justify our optimism of achieving our goal - a general description of the average evolution of the Universe. The complementary result concerning the averaging on the light cone has been accomplished. Model-independent determination of luminosity distances and redshift drift in general inhomogeneous spacetimes have been accomplished.
A direct answer to the main question of ARTHUS, i.e. whether we can explain observations without the need for dark energy, has been given with the astonishing outcome that not only we find a dark energy-free model to explain supernova observations
[ https://arxiv.org/abs/1902.07915 ], but also that we simultaneously solved further questions that were recently raised in the community [ https://arxiv.org/abs/2002.10831 ].
Until the end of the project we shall aim at enhancing and finalizing the results above.
We have furthermore obtained many 'solid' results on models and statistical tools, their application falling into the last period before the end of ARTHUS. Here, we concentrate on the morpho-statistical analysis of observational data (Cosmic Microwave Background for finite universe models, analysis of galaxy catalogs and new interpretations of the catalogs with distance measures that account for the curvature evolution, updated supernova catalogs to improve our results).