# K-mouflage Cosmology: Formation of Large-Scale Structures

Abstract : We study structure formation in K-mouflage cosmology whose main feature is the absence of screening effect on quasi-linear scales. We show that the growth of structure at the linear level is both affected by a new time dependent Newton constant and a friction term which depend on the background evolution. These combine with the modified background evolution to change the growth rate by up to ten percent since $z\sim 2$. At the one loop level, we find that the non-linearities of the K-mouflage models are mostly due to the matter dynamics and that the scalar perturbations can be treated at tree level. We also study the spherical collapse in K-mouflage models and show that the critical density contrast deviates from its $\Lambda$-CDM value and that, as a result, the halo mass function is modified for large masses by an order one factor. Finally we consider the deviation of the matter spectrum from $\Lambda$-CDM on non-linear scales where a halo model is utilised. We find that the discrepancy peaks around $1\ h{\rm Mpc}^{-1}$ with a relative difference which can reach fifty percent. Importantly, these features are still true at larger redshifts, contrary to models of the chameleon-$f(R)$ and Galileon types.
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https://hal-cea.archives-ouvertes.fr/cea-00982373
Contributor : Emmanuelle de Laborderie <>
Submitted on : Wednesday, April 23, 2014 - 5:09:33 PM
Last modification on : Wednesday, September 12, 2018 - 2:13:46 PM

### Identifiers

• HAL Id : cea-00982373, version 1
• ARXIV : 1403.5424

### Citation

Philippe Brax, Patrick Valageas. K-mouflage Cosmology: Formation of Large-Scale Structures. 2014. ⟨cea-00982373⟩

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