Perturbing a quantum gravity condensate

Understand

In a recent proposal using the group field theory approach, a spatially homogeneous (generally anisotropic) universe is described as a quantum gravity condensate of "atoms of space," which allows the derivation of an effective cosmological Friedmann equation from the microscopic quantum gravity dynamics.

• Here we take a first step towards the study of cosmological perturbations over the homogeneous background.
• We consider a state in which a single "atom" is added to an otherwise homogeneous condensate.
• Backreaction of the perturbation on the background is negligible and the background dynamics can be solved separately.