Identifying cosmological perturbations in group field theory condensates

Understand

One proposal for deriving effective cosmological models from theories of quantum gravity is to view the former as a mean-field (hydrodynamic) description of the latter, which describes a universe formed by a 'condensate' of quanta of geometry.

• This idea has been successfully applied within the setting of group field theory (GFT), a quantum field theory of 'atoms of space' which can form such a condensate.
• We further clarify the interpretation of this mean-field approximation, and show how it can be used to obtain a semiclassical description of the GFT, in which the mean field encodes a classical statistical distribution of geometric data.
• In this sense, GFT condensates are quantum homogeneous geometries that also contain statistical information about cosmological inhomogeneities.