Zero-parameter extension of general relativity with a varying cosmological constant

@article{Alexander2019ZeroparameterEO,
  title={Zero-parameter extension of general relativity with a varying cosmological constant},
  author={Stephon H. S. Alexander and Marina Cort{\^e}s and Andrew R. Liddle and Jo{\~a}o Magueijo and Robert Sims and Lee Smolin},
  journal={Physical Review D},
  year={2019}
}
We provide a new extension of general relativity (GR) which has the remarkable property of being more constrained than GR plus a cosmological constant, having one less free parameter. This is implemented by allowing the cosmological constant to have a consistent space-time variation, through coding its dynamics in the torsion tensor. We demonstrate this mechanism by adding a `quasi-topological' term to the Einstein action, which naturally realizes a dynamical torsion with an automatic… 

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