Abstract

I discuss how we can constrain in a model-independent way the nature of dark energy. Dark energy can be a classical cosmological constant, a scalar field or just gravity being modified at large scales. As the number of models grows, the observational constraints become more tenuous. I will show how new tests can be implemented beyond the classical SN or weak lensing and how a new formalism can be used to unveil the nature of the scalar field driving expansion today. I will show current constraints from new data sets and discuss where we stand today regarding the nature of dark energy.