Constraints on background torsion field from K physics
  We point out that a background torsion field will produce an effective potential to the $K$ and $\bar{K}$ with opposite signs. This allows us to constrain the background torsion field from the $K_L$ and $K_S$ mass difference, CPT violating $K^\circ$ and $\bar{K^\circ}$ mass difference and the CP violating quantities $\epsilon$ and $\eta_{+-}$. The most stringent bound on the cosmological background torsion $< T^0 > < 10^{-25}$ GeV comes from the direct measurement of the CPT violation. 
Subhendra Mohanty and Utpal Sarkar