Abstract
This paper is concerned with the death-birth updating process. This model is an
example of a spatial game in which players located on the d -dimensional integer
lattice are characterized by one of two possible strategies and update their strategy
at rate one by mimicking one of their neighbors chosen at random with a probability
proportional to the neighbor’s payoff. To understand the role of space in the form of
local interactions, the process is compared with its nonspatial deterministic counter-
part for well-mixing populations, which is described by the replicator equation. To
begin with, we prove that, provided the range of the interactions is sufficiently large,
both strategies coexist on the lattice for a parameter region where the replicator
equation also exhibits coexistence. Then, we identify parameter regions in which
there is a dominant strategy that always wins on the lattice whereas the replicator
equation displays either coexistence or bistability. Finally, we show that, for the
one-dimensional nearest neighbor system and in the parameter region corresponding
to the prisoner’s dilemma game, cooperators can win on the lattice whereas defectors
always win in well-mixing populations, thus showing that space favors cooperation.
In particular, several parameter regions where the spatial and nonspatial models
disagree are identified.
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