CASUS Institute Seminar, Prof. Daniel Sebastiani, Martin Luther University Halle-Wittenberg, Germany

Abstract of the talk// A fundamental assumption of standard cosmology is that the spatial distribution of matter on large-enough scales is very close to homogeneous and isotropic. This is referred to as the cosmological principle. When studying the catalogues of visible tracers like galaxies, gamma ray bursts and quasars, a consistency check thus involves verifying, first, that a homogeneous distribution is recovered on scales predicted by the model, if recovered at all, and secondly, that the unusual structures identified in different samples are allowed in the adopted cosmology [MNRAS 434, 398 (2013)]. The latter point drives the ongoing attempts to accurately predict the largest possible size of structures from theory (and simulations) and confront the available observational estimates drawn from such catalogues.

According to the recently introduced screening formalism, gravitational interactions obey the Yukawa-law on cosmological scales and exhibit exponential decay beyond the characteristic screening length, conveniently providing an upper-bound on the gravitationally-bound individual structure size. In this talk, Daniel will take a closer look at the growth of density fluctuations as formulated in the screening approach, focusing on the small-wavelength modes, i.e., gigaparsec scales. He will compare the matter power spectrum obtained via N-body simulations with the analytical predictions based on fluid approximation, where appropriate.

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