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Abstract: We investigate the clustering of dark energy within matter overdensities andvoids. In particular, we derive an analytical expression for the dark energydensity perturbations, which is valid both in the linear, quasi-linear andfully non-linear regime of structure formation. We also investigate thepossibility of detecting such dark energy clustering through the ISW effect. Inthe case of uncoupled quintessence models, if the mass of the field is of orderthe Hubble scale today or smaller, dark energy fluctuations are always smallcompared to the matter density contrast. Even when the matter perturbationsenter the non-linear regime, the dark energy perturbations remain linear. Wefind that virialised clusters and voids correspond to local overdensities indark energy, with $\delta {\phi}-1+w \sim \Oo10^{-5}$ for voids,$\delta {\phi}-1+w \sim \Oo10^{-4}$ for super-voids and$\delta {\phi}-1+w \sim \Oo10^{-5}$ for a typical virialised cluster. Ifvoids with radii of $100-300 { m Mpc}$ exist within the visible Universe then$\delta {\phi}$ may be as large as $10^{-3}1+w$. Linear overdensities ofmatter and super-clusters generally correspond to local voids in dark energy;for a typical super-cluster: $\delta {\phi}-1+w \sim \Oo-10^{-5}$. Theapproach taken in this work could be straightforwardly extended to study theclustering of more general dark energy models.

Author: David F. Mota, Douglas J. Shaw, Joseph Silk

Source: https://arxiv.org/

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