Multitype Contact Process on $\mathbb{Z}$: Extinction and Interface

We consider a two-type contact process on $\mathbb{Z}$ in which both types have equal finite range and supercritical infection rate. We show that a given type becomes extinct with probability 1 if and only if, in the initial configuration, it is confined to a finite interval $[-L,L]$ and the other type occupies infinitely many sites both in $(-\mathrm{\infty },L)$ and $(L,\mathrm{\infty })$. We also show that, starting from the configuration in which all sites in $(-\mathrm{\infty },0]$ are occupied by type 1 particles and all sites in $(0,\mathrm{\infty })$ are occupied by type 2 particles, the process ${\rho }_t$ defined by the size of the interface area between the two types at time $t$ is tight.