Spin-particles entanglement in Robertson-Walker spacetime

We study the entanglement between two modes of Dirac field in an expanding spacetime characterized by the Robertson-Walker metric. This spacetime model turns out to be asymptotically (in the remote past and far future regions) Minkowskian. Then, on the one hand we show entanglement creation between particles and antiparticles when passing from remote past to far future. On the other hand, we show that particles entanglement in the remote past degrades into the far future. These effects are traced back to particle creation. In our analysis we highlight the role of spin (polarization) of particles and compare the results with those obtainable without accounting for it.