No. In general relativity torsion doesn't play any role, it can be consistently set to zero. Only if there exist fields, beyond the mettic, that determine the spacetime geometry, does torsion play a role. This would be seen through violations of the equivalence principle, that, for the moment, haven't been observed.

Mr Nichols,

Well, Konstantinov found this effect, regarding coupling of torsion and Spin: Torsion is linked to the intrinsic spin of matter, suggesting that gravitational effects can be influenced by the spin of particles, which is not accounted for in traditional theories.

That torsion couples to spin isn't anything new. However in general relativity, once more, torsion doesn't play any role, because it is always possible to set it equal to zero. And the reason this is possible is because, if the only field that defines the spacetime geometry is the metric, the only field, that describes how matter is affected by and can affect the spacetime geometry is the energy-momentum tensor of matter, not the fields that define the properties of matter, such as spin. And that's because the coupling of the spacetime geometry and matter must be invariant under general coordinate transformations.

In theories, that generalize general relativity, such as scalar-tensor theories and supergravity, additional fields, besides the metric, define the spacetime geometry. The coupling of these fields to matter, in a way that is invariant under general coordinate transformations, is sensitive to the properties of the matter fields themselves, in particular, spin; in these theories torsion cannot be consistently eliminated. However such theories, therefore, imply, by definition, violations of the equivalence principle, which is, precisely, what the additional terms describe. So far the presence of these terms hasn’t been seen in experiments.

Mr Nichols,

Υes but as far as I understand Einstein choose curvature because its tensor was compatible with the energy tensor to form the field equations (and also avoided the conflicts you said) but such a rational is mathematical and of little physical Insight. Thats why the torsion theories maybe come up

History is different from technical content. How and why Einstein made his choices is a matter of history; how they’re understood to be correct and what they mean only matters. The physical insight is in the symmetries, in the case at hand invariance under general coordinate transformations. And this symmetry implies just what the interactions can be. That wasn’t understood in this way by Einstein, but by Emmy Noether, but that doesn’t matter anymore.

The question

“Have Torsion in Spacetime theories identified detectable new phenomena?”

- has the really scientific answer “No”, first of all since in the Shevchenko-Tokarevsky’s Planck scale informational physical model, in this case it is enough to read paper

https://www.researchgate.net/publication/383127718_The_Informational_Physical_Model_and_Fundamental_Problems_in_Physics ,

- it is rigorously scientifically proven that Matter’s spacetime is fundamentally absolute, fundamentally flat, fundamentally continuous, and fundamentally “Cartesian”, (at least) [4+4+1]4D with metrics (at least) (cτ,X,Y,Z, g,w,e,s,ct), ct is the real tome dimension,

- and so the spacetime principally by no means can be impacted by anything in Matter, and by no means can impact on anything in Matter. It is fundamentally nothing else than some empty container with fundamentally infinite dimensions above; including in the spacetime by no means can be any “torsions”.

What is a fundamental Nature force “Gravity” [and Electric and Nuclear/Strong Forces as well, though] more see the link above, section 6 “Mediation of the fundamental forces in complex systems”.

More see the link, here only note, that Gravity Force has a number of traits that Electric Force has, including, say, the gravitational [“gravitational mass”] and Electric charge fundamentally similarly are written on particles [algorithms], which [particles] really rotate having 4D angular momentums M at least in the utmost universal “kinematical” space with 4D metrics (cτ,X,Y,Z), what in 3DXYZ space is observed as particles’ “spins”, which are 3D projections of M.

Correspondingly Electric Force isn’t “completely electric” one, so even particles, and more essentially atoms, that have non-zero spins/some electrons orbital momentums, have magnetic momentums,

- What reveals itself in well observed stationary magnetic effects – including observed on macro scale in magnets, where some atoms are “polarized” by external stationary magnetic field.

So, in principle, some stationary gravimagnetic fields [besides “kinematical” gravimagnetic fields, which practically for sure are created by moving in the 3D space gravitational masses – as that happens when electric charges move] can exist,

- however it looks as that practically negligible effect on macroscale, since in Gravity case – unlike Electric Force - really it is impossible to create corresponding external gravimagnetic field, which would “polarize” gravimagnetic momentums on micro scale

Cheers

Mr Nichols,

I agree that equivalence principle and relativistic ones are highly physical intuitive enrichments of orthodox curvature-based formulation of General Relativity (aside from its empirical confirmations) but 1)Nobody excludes the possible discovery of a physical intuitive principle related to the tortional formulation of gravity 2) the epistemic weight of relativistic principles is not guaranteed to not be overrated at this time of history and 3) it is a fact that Einstein dropped out an important principle in his formulation of GR, Mach's, it being not compatible with the "more suitable" and all (rest) - encompassing one he brainstormed (standard established formulation)