Develop an analogous criterion for the non-periodic case

Develop an analogue of the periodic-flow criterion that ensures non-local exponentiality for C^∞(M) ⋊_α R in the case of non-periodic flows σ: R × M → M on compact manifolds M by identifying verifiable conditions under which the exponential map fails to be a local diffeomorphism at the identity.

Background

Within Section 3, the authors present criteria establishing non-local exponentiality for several situations, including periodic flows on compact manifolds, and they derive concrete non-surjectivity of the associated β_s operators. They note that these results yield non-local exponentiality in various cases.

However, they point out a gap for non-periodic flows, stating that an analogous criterion has not been proved, and they express the belief that such groups are never locally exponential—echoing the broader Conjecture A.

References

Unfortunately, we were not able to prove an analogous criterion for the non-periodic case, but we find it very likely that the groups C (M) ⋊ R are never locally exponential.

On the singularities of the exponential function of a semidirect product (2408.15053 - Chirvasitu et al., 27 Aug 2024) in Section 3, after Corollary 3.14