Spin network coherent states for planar gravitational waves. I

TL;DR

This paper develops coherent states for spin networks with planar symmetry in loop quantum gravity, revealing an unexpected O(3) symmetry and providing a basis for approximate eigenstates useful for volume operator calculations.

Contribution

It introduces a novel construction of coherent states for planar spin networks that incorporate an emergent O(3) symmetry, extending prior SU(2) frameworks.

Findings

Coherent states obey an emergent O(3) symmetry.

States are superpositions of holonomies with residual U(1) symmetry on average.

Operators produce states with small correction terms.

Abstract

This paper constructs coherent states for spin networks with planar symmetry. After gauge-fixing, the full SU(2) symmetry is broken to U(1), but one cannot simply use the U(1) limit of SU(2) coherent states, because the planar states exhibit an unexpected O(3) symmetry arising from the closed loop character of the transverse directions. The coherent states constructed in this paper obey this symmetry. They are superpositions of holonomies which obey the residual U(1) symmetry only on average; some holonomies in the superposition violate the symmetry, although the U(1) quantum numbers of these holonomies are peaked at values which obey the symmetry. Operators acting on coherent states give back a c-number times the original state, plus small correction states, which make the coherent state an approximate, rather than exact eigenstate of the operator. In a follow-on paper, these small correction states are used to calculate small corrections to the volume operator.