A new solution for a generalized cosmological wormhole

Abstract

We find a new exact solution to Einstein field equations that represents a cosmological wormhole embed- ded in a flat Friedmann–Lemaître–Robertson–Walker uni- verse. The new metric is a generalization of a previous cos- mological wormhole solution found by Kim. We explicitly show that the flaring out condition is satisfied at the throat at all cosmic times; in addition, the null energy condition is violated at the throat regardless of the background cosmo- logical model; thus, the spacetime geometry presented here describes a wormhole coupled to the cosmic dynamics that exists at all cosmic times and whose throat remains open in any cosmological model.