  Recent contributions address the problem of language coexistence as that of
two species competing to aggregate speakers, thus focusing on the dynamics of
linguistic traits across populations. They draw inspiration from physics and
biology and share some underlying ideas -- e. g. the search for minimal schemes
to explain complex situations or the notion that languages are extant entities
in a societal context and, accordingly, that objective, mathematical laws
emerge driving the aforementioned dynamics. Different proposals pay attention
to distinct aspects of such systems: Some of them emphasize the distribution of
the population in geographical space, others research exhaustively the role of
bilinguals in idealized situations (e. g. isolated populations), and yet others
rely extremely on equations taken unchanged from physics or biology and whose
parameters bear actual geometrical meaning. Despite the sources of these models
-- so unrelated to linguistics -- sound results begin to surface that establish
conditions and make testable predictions regarding language survival within
populations of speakers, with a decisive role reserved to bilingualism. Here we
review the most recent works and their interesting outcomes stressing their
physical theoretical basis, and discuss the relevance and meaning of the
abstract mathematical findings for real-life situations.
