Recent results have shown how quantum cosmology models can be derived from the effective dynamics of condensate states in group field theory ( GFT ) , where ‘ cosmology is the hydrodynamics of quantum gravity ’ : the classical Friedmann dynamics for homogeneous , isotropic universes , as well as loop quantum cosmology ( LQC ) corrections to general relativity have been shown to emerge from fundamental quantum gravity .
We take one further step towards strengthening the link with LQC and show , in a class of GFT models for gravity coupled to a free massless scalar field and for generic initial conditions , that GFT condensates dynamically reach a low spin phase of many quanta of geometry , in which all but an exponentially small number of quanta are characterised by a single spin j _ { 0 } ( i.e .
by a constant volume per quantum ) .
As the low spin regime is reached , GFT condensates expand to exponentially large volumes , and the dynamics of the total volume follows precisely the classical Friedmann equations .
This behaviour follows from a single requirement on the couplings in the GFT model under study .
We present one particular simple case in which the dominant spin is the lowest one : j _ { 0 } = 0 or , if this is excluded , j _ { 0 } = 1 / 2 .
The type of quantum state usually assumed in the derivation of LQC is hence derived from the quantum dynamics of GFT .
These results confirm and extend recent results by Oriti , Sindoni and Wilson-Ewing in the same setting .