Entanglement time in the primordial universe

Understand

We investigate the behavior of the entanglement entropy of space in the primordial phase of the universe before the beginning of cosmic inflation.

• We argue that in this phase the entanglement entropy of a region of space grows from a zero-law to an area-law.
• This behavior provides a quantum version of the classical BKL conjecture that spatially separated points decouple in the approach to a cosmological singularity.
• We show that the relational growth of the entanglement entropy with the scale factor provides a new statistical notion of arrow of time in quantum gravity.