A cosmic glitch in gravity

Understand

We investigate a model that modifies general relativity on cosmological scales, specifically by having a `glitch' in the gravitational constant between the cosmological (super-horizon) and Newtonian (sub-horizon) regimes, as motivated e.g.

• in the Ho\v{r}ava-Lifshitz proposal or in the Einstein-aether framework.
• This gives a single-parameter extension to the standard $\Lambda$CDM model, which is equivalent to adding a dark energy component, but where the energy density of this component can have either sign.
• Fitting to data from the Planck satellite, we find that negative contributions are, in fact, preferred.