# Constraining DGP Gravity from Observational Data

## TL;DR

This paper constrains a phenomenological model interpolating between DM and DGP gravity using current cosmological data, finding the flat DGP model incompatible with observations and projecting future improvements.

## Contribution

It provides the first tight observational constraints on the DM-DGP interpolation parameter lpha, demonstrating current data disfavors the flat DGP model.

## Key findings

- The parameter lpha=0.254b1 0.153 (68% C.L.)
- Flat DGP model is incompatible with current observations
- Future measurements could improve constraints on lpha by a factor of two.

## Abstract

The accelerating expansion of our universe at present could be driven by an unknown energy component (Dark Energy) or a modification of general relativity (Modified Gravity). In this note we revisit the constraints on a phenomenological model which interpolates between the pure \LambdaCDM model and the Dvali-Gabadadze-Porrati (DGP) braneworld model with an additional parameter \alpha. Combining the cosmic microwave background (CMB), baryon acoustic oscillations (BAO) and type Ia supernovae (SNIa), as well as some high-redshift observations, such as the gamma-ray bursts (GRB) and the measurements of linear growth factors (LGF), we obtain the tight constraint on the parameter \alpha=0.254\pm0.153 (68% C.L.), which implies that the flat DGP model is incompatible with the current observations, while the pure \LambdaCDM model still fits the data very well. Finally, we simulate the future measurements with higher precisions and find that the constraint on \alpha can be improved by a factor two, when compared to the present constraints.