Revisiting the cuscuton as a Lorentz-violating gravity theory
  The cuscuton is a scalar field with infinite speed of propagation. It was introduced in the context of cosmology but it has also been claimed to resemble Horava gravity in a certain limit. Here we revisit the cuscuton theory as a Lorentz-violating gravity theory. We clarify its relation with Horava gravity and Einstein-aether theory, analyze its causal structure, and consider its initial value formulation. Finally, we discuss to which extent the cuscuton theory can be used as a proxy for Horava gravity in the context of gravitational collapse and formation of universal horizons. 
Jishnu Bhattacharyya, Andrew Coates, Mattia Colombo, A. Emir   Gumrukcuoglu, Thomas P. Sotiriou
hep-th astro-ph.CO gr-qc