Abstract
J. Stat. Mech. (2006) P12007 We analyze from the renormalization group perspective a universality class of
reaction-diffusion systems with absorbing states. It describes models where the
vacuum state is not accessible, as the set of reactions $2 A \to A$ together
with creation processes of the form $A \to n A$ with $n \geq 2$. This class
includes the (exactly solvable in one-dimension) {\it reversible} model $2 A
\leftrightarrow A$ as a particular example, as well as many other {\it
non-reversible} reactions, proving that reversibility is not the main feature
of this class as previously thought. By using field theoretical techniques we
show that the critical point appears at zero creation-rate (in accordance with
exact results), and it is controlled by the well known pair-coagulation
renormalization group fixed point, with non-trivial exactly computable critical
exponents in any dimension. Finally, we report on Monte-Carlo simulations,
confirming all field theoretical predictions in one and two dimensions for
various reversible and non-reversible models.