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Title: Constraining Dark Energy and Modified Gravity with Euclid: What to do about model-independence and non-linearities?

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Abstract:The standard cosmological model LCDM is still the best fit to present observations. However, theoretical motivations and the presence of mild tensions in the data, motivate us to look for further explanations to the accelerated expansion of the Universe. Future galaxy redshift surveys such as Euclid, DESI and LSST will provide unprecedented volumes of precision data that will help us discriminate between alternative models of gravity that offer alternative explanations to the cosmological constant. In order to understand these data, we need to be able to model non-linearities, model cross-correlations among probes and have unbiased parametrizations of theoretical modified gravity models.
First, I will present some recent progress in using Galaxy Clustering, Weak Lensing and Cross Correlations to improve the forecasted errors on the equation of state of Dark Energy within forecasts for Euclid. Then I will discuss parametrization-free approaches for constraining the Sigma and Mu functions in modified gravity in the linear and non-linear regime, followed by a model-independent method of estimating the gravitational slip with future redshift surveys and galaxy cluster samples.

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