# Non-locality and Dark Energy

#### Principal Investigators: V. Mukhanov, I. Sachs (LMU Munich)

## Summary

Certain covariantly consistent infrared modifications of the Einstein equations have the potential of
explaining late time cosmological expansion since they interpolate between the Planck scale of the
gravitational coupling constant and the long distance gravitational constant. Such modifications can
arise from non-local contributions to the effective action for the gravitational field. While non-locality
is a generic feature of quantum fields coupled to classical gravity this does not imply that any such
model will be relevant for late time acceleration. The crucial question is whether one is able to extract
the terms that are relevant for late time acceleration or Dark Energy. This is the focus of the project
described here.

### Role within the Transregional Collaborative Research Centre

A close interaction with the projects A1, A2, A3, A6 is anticipated. We will make predictions that
can be tested in B3 and B5.

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