Gaussian averaging versus group averaging for noncompact gauge groups

Determine whether the Gaussian average over exterior matter states is superfluous for tensor networks with non-compact gauge groups, or whether it supplies an independent operation beyond the renormalizing group average implemented by the operator-valued weight.

Background

The paper uses a Gaussian ensemble of matter states to obtain minimization over generalized entropies and to model ignorance of exterior matter. The authors observe that the Gaussian ensemble average and the operator-valued weight implementing group averaging both define maps from the full bounded-operator algebra to the gauge-invariant algebra.

This raises an unresolved question about whether randomness is an additional physical assumption or is already effectively generated by gauge averaging, particularly for noncompact gauge groups.

References

It would be very interesting to determine whether the Gaussian average is in fact superfluous for non-compact gauge groups. We leave this for future work.

Topological entanglement entropy in 3D gravity  (2609.19247 - Balasubramanian et al., 16 Sep 2026) in Section 3.1, Random exterior