# Linear perturbations in viable f(R) theories

Nelson A. Lima, Andrew R. Liddle

Research output: Contribution to journalArticlepeer-review

## Abstract

We describe the cosmological evolution predicted by three distinct $f(R)$ theories, with emphasis on the evolution of linear perturbations. The most promising observational tools for distinguishing $f(R)$ theories from $\Lambda$CDM are those intrinsically related to the growth of structure, such as weak lensing. At the linear level, the enhancement in the gravitational potential provided by the additional $f(R)$ `fifth force' can separate the theories, whereas at the background level they can be indistinguishable. Under the stringent constraints imposed on the models by Solar System tests and galaxy-formation criteria, we show that the relative difference between the models' linear evolution of the lensing potential will be extremely hard to detect even with future space-based experiments such as {\it Euclid}, with a maximum value of approximately 4% for small scales. We also show the evolution of the gravitational potentials under more relaxed local constraint conditions, where the relative difference between these models and $\Lambda$CDM could prove discriminating.
Original language English 043521 Physical Review D 88 https://doi.org/10.1103/PhysRevD.88.043521 Published - 5 Jul 2013

• astro-ph.CO

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