Two-fluid evolving Lorentzian wormholes
  We investigate the evolution of a family of wormholes sustained by two matter components: one with homogeneous and isotropic properties $\rho(t)$ and another inhomogeneous and anisotropic $\rho_{in}(t,r)$. The rate of expansion of these evolving wormholes is only determined by the isotropic and homogeneous matter component $\rho(t)$. Particularly, we consider a family of exact two-fluid evolving wormholes expanding with constant velocity and satisfying the dominant and the strong energy conditions in the whole spacetime. In general, for the case of vanishing isotropic fluid $\rho(t)$ and cosmological constant $\Lambda$ the space expands with constant velocity, and for $\rho(t)=0$ and $\Lambda \neq 0$ the rate of expansion is determined by the cosmological constant. The considered here two-fluid evolving wormholes are a generalization of single fluid models discussed in previous works of the present authors [Phys.\ Rev.\ D {\bf 78}, 104006 (2008); Phys.\ Rev.\ D {\bf 79}, 024005 (2009)]. 
Mauricio Cataldo and Sergio del Campo
gr-qc hep-th