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Structure formation in the presence of dark interactions

Marco Baldi
ITP, Heidelberg/MPA, Garching

In the last decade a large number of independent and complementary cosmological observations has provided clear evidence that the expansion of the Universe has started to accelerate since about six billion years. This acceleration can be accounted for by a dark energy component with a negative equation of state, whose fundamental  nature represents one of the most central problems in modern astrophysics and in physics in general. Although the simplest scenario based on a cosmological constant fits remarkably well most of the presently available data, it also raises deep conceptual puzzles related to the extreme fine-tuning it requires to match observations.

In order to overcome such problems, dynamical dark energy models based on the evolution of a cosmological scalar field (as e.g. quintessence or k-essence) have been proposed and widely studied in the recent past. Among these, a particularly interesting class is given by interacting dark energy models, where the scalar field directly interacts with other cosmic components by exchanging energy during its evolution. As a consequence of this interaction the scalar field mediates a new long-range fifth-force between massive particles.

Interacting dark energy models (as e.g. coupled quintessence) had been so far investigated only concerning their cosmological background and linear perturbations evolution, allowing to put rough bounds on the strength of the interaction, while a clear understanding of their impact on the nonlinear regime of structure formation was still a missing piece of information.

Studying and understanding the properties of nonlinear structures forming in interacting dark energy cosmologies might provide a deeper insight into the dark energy issue, and might offer a unique tool to identify specific features of this scenario. However, to this end one necessarily needs to rely on the outcomes of detailed and computationally demanding numerical simulations, which have to be specifically devised for these non-standard cosmological models.

In the present talk I will review the main features and motivations of the interacting dark energy scenario, and I will present the numerical implementation of such models in the N-body algorithm of the cosmological simulations code GADGET-2. I will then present the results of the first fully self-consistent high-resolution N-body simulations of interacting dark energy models, highlighting the main effects that the interaction induces in the properties of highly non-linear structures. I will finally discuss the future prospects in the investigation of interacting dark energy cosmologies, with a particular stress on the possible coupling between dark energy and the cosmic background of massive neutrinos.

2009 July 08, 15:39

Centro de Astrofísica da Universidade do Porto (Auditorium)
Rua das Estrelas, 4150-762 Porto

Instituto de Astrofísica e Ciências do Espaço Universidade do Porto Faculdade de Ciências da Universidade de Lisboa
Fundação para a Ciência e a Tecnologia COMPETE 2020 PORTUGAL 2020 União Europeia