Cosmological bounces and Lorentzian wormholes in Galileon theories with   an extra scalar field
  We study whether it is possible to design a "classical" spatially flat bouncing cosmology or a static, spherically symmetric asymptotically flat Lorentzian wormhole in cubic Galileon theories interacting with an extra scalar field. We show that bouncing models are always plagued with gradient instabilities, while there are always ghosts in wormhole backgrounds. 
R. Kolevatov and S. Mironov
hep-th astro-ph.CO gr-qc