Theoretical construction of wormholes supported by Chaplygin gas
  The purpose of this paper is to examine the possible existence or construction of traversable wormholes supported by generalized Chaplygin gas (GCG) by starting with a general line element and the Einstein tensor, together with the equation of state, thereby continuing an earlier study by the author of wormholes supported by phantom energy. Numerical techniques are used to demonstrate the existence of wormhole spacetimes that (1) meet the flare-out conditions at the throat, (2) are traversable by humanoid travelers, thanks to low tidal forces and short proper distances near the throat, and (3) are asymptotically flat. There appears to be an abundance of solutions that avoid an event horizon, suggesting the possibility of naturally occurring wormholes. 
Peter K.F. Kuhfittig