Extending Einstein’s theory of General Relativity (which describes gravity) by adding a special kind of field called an "axial vector field" that represents spacetime torsion is an idsathst comes and goes without convinvibg theoretical argument pro or active experimental research to disprove it.

Torsion is a way of describing how spacetime might twist, not just curve. The key point is that this extension does not require inventing new particles or forces beyond what already exists in the Standard Model of particle physics.

- In some theories, like A. Rizzo's, the axial vector field interacts with the "spin" of particles, especially fermions (like electrons and quarks), which are the building blocks of matter.

- These theories predicts new, very weak forces between spinning particles and possible effects on light as it travels through space.

- The strength of this torsion effect is fixed by consistency with known physics, so there is little freedom to adjust it arbitrarily.

Further insights & discussion

- In standard General Relativity, spacetime is curved by mass and energy, but it is assumed not to have torsion (twisting).

- Generalizing the theory by allowing spacetime to have torsion, described by an axial vector field has several physical consequences

- The torsion field acts like a massive vector field, meaning it has a mass and can mediate a force, but only over very short distances (set by the mass).

- Two main laboratory effects are predicted by theories such as Rizzo's:

- A new "spin-dipole" force between particles with spin, but this force is extremely weak and only relevant at very short distances.

- A possible coupling to photons (light), which could cause very tiny changes in the polarization of light traveling through space (birefringence)