Curvature-Gated Collapse

01The evidence

• Matter-wave interferometry has reached the mass and complexity range where objective-reduction models make testable predictions. Protected aromatic systems such as pentacene-doped naphthalene are now proposed as interferometric test masses.NACE interferometer proposal, 2026

02The tension

Decoherence experiments keep pushing mass and separation upward without finding the collapse threshold. Either the effect is weaker than predicted, or the models are using the wrong gravitational quantity. Every experiment so far has been done in one gravitational environment, so the models have never been separated.

03The theory

The Penrose argument uses the gravitational self-energy of the superposition. That is a measure of how much curvature the two branches would produce. But curvature is not a scalar, and the part that ought to matter is its gradient: the tidal field, the piece that cannot be removed by changing frame.

If collapse is gated by the tidal field, then a free-falling apparatus in orbit sits in a different regime from one on a laboratory bench, even at identical mass and separation. The ground experiment feels the Earth's gradient continuously; the orbiting one feels almost none, apart from the gradient of its own spacecraft.

The same reasoning makes the effect anisotropic. Near a rotating mass the tidal tensor has off-diagonal terms, so rotating the interferometer changes the predicted rate without changing anything else. That is an unusual prediction: decoherence becoming orientation-dependent is not something standard environmental decoherence does.

The proposal is uncomfortable because it modifies a model that is already speculative. But it is the version that can be tested with hardware that exists, and it converts a philosophical question into an engineering one.

04What this is not

05Predictions

• P1The same interferometer, at the same mass and separation, should show a fringe-visibility difference of at least one part in a thousand between a ground laboratory and a free-falling platform.
• P2Rotating the apparatus relative to a nearby large mass should change the decoherence rate at fixed environmental noise.
• P3The apparent mass threshold for collapse should shift with altitude by a predictable factor.

06What would refute it

Identical decoherence rates to one part in ten thousand across gravitational environments would refute the gradient dependence and leave mass-only models standing.

07What it would change

It turns quantum gravity from an untestable limit into a space mission, and makes decoherence a probe of the gravitational field rather than a nuisance to be shielded.