Measurement outcomes for the spherically symmetric 4D exotic wavefunction

Determine whether measurements of the spherically symmetric s-wave four-dimensional wavefunction—obtained by interpreting the two-dimensional transformed state as the s-wave component of four-dimensional fermions and attached to a volume defect between two spherical shells—yield spherically symmetric detection outcomes or angularly localized events; specify and analyze concrete measurement protocols to resolve this question and characterize how the answer depends on the measurement details.

Background

After constructing explicit two-dimensional wavefunctions for exotic excitations scattered by the Maldacena–Ludwig wall, the authors note that the same expressions can be used as the s-wave part of a four-dimensional fermionic scattering state. In this four-dimensional interpretation, the state is spherically symmetric and can be viewed as being attached to a volume defect between two spherical shells.

The authors explicitly raise the question of what a measurement would observe in such a state: whether detection outcomes remain spherically symmetric or become localized in angle. They acknowledge uncertainty and emphasize that a definitive answer requires specifying the measurement protocol, highlighting an unresolved problem at the interface of quantum measurement and the constructed scattering states.

References

The four-dimensional wavefunction suggested in A\ref{Q:4d} is spherically symmetric, and would be `attached' in the sense of A\ref{Q:defect} to a volume-defect filling the region between two spherical shells. What happens when we measure this wavefunction? Do we get a spherically-symmetric result, or a result localized in the angular direction? The authors are not sure, but the following discussion might be of some use.

— What happens to wavepackets of fermions when scattered by the Maldacena-Ludwig wall?  (2603.25508 - Tachikawa et al., 26 Mar 2026) in Section 4 (Conclusions and Outlook), Q&A: final question