  The restricted diffusive pair contact process 2A->3A, 2A->0 (PCPD) and the
classification of its critical behavior continues to be a challenging open
problem of non-equilibrium statistical mechanics. Recently Kockelkoren and
Chate [Phys. Rev. Lett. 90, 125701 (2003)] suggested that the PCPD in one
spatial dimension represents a genuine universality class of non-equilibrium
phase transitions which differs from previously known classes. To this end they
introduced an efficient lattice model in which the number of particles per site
is unrestricted. In numerical simulations this model displayed clean power
laws, indicating ordinary critical behavior associated with certain non-trivial
critical exponents. In the present work, however, we arrive at a different
conclusion. Increasing the numerical effort, we find a slow drift of the
effective exponents which is of the same type as observed in previously studied
fermionic realizations. Analyzing this drift we discuss the possibility that
the asymptotic critical behavior of the PCPD may be governed by an ordinary
directed percolation fixed point.
