Waldyr Rodrigues Jr's & Hagen Kleinert's books on Gravity as Plastic Distortion

Hagen Kleinert has published papers and books on this as well. The basic idea is that the spacetime manifold is emergent in the sense of Wheeler's IT FROM BIT where Einstein's curvature field corresponds to disclination topological defects in a 4D world crystal lattice. A torsion field corresponds to dislocation topological defects. 

If the 't Hooft-Susskind-Ng hologram principle is correct, then the world crystal lattice spacing is ~ (Planck area Hubble scale)^1/3 ~ 1 fermi consistent with Abdus Salam's f-gravity.

In addition, I have a model where the tetrads and spin connections of the gravity field come from the 8 coherent gluon strong force Goldstone phases of the QCD vacuum superconductor described by Frank Wilczek in the "Lightness of Being."

For Waldyr's book click here. For a free paper with his basic idea click here. Warning most physicists will find the notation hard to follow. The basic idea uses the tetrads that are the spin 1 "square roots" of Einstein's spin 2 metric tensor fields. For a more physical picture click here.

For Hagen's books click here.