Critical and tricritical exponents of the Potts lattice gas

Critical and tricritical exponents for the two-dimensionalq-state Potts lattice gas are calculated using a Kadanoff lower-bound renormalization transformation with three variational parameters. The calculations support the picture proposed by Nienhuis et al. in which the critical and tricritical fixed points annihilate atq=4. For the most part, the exponents are in excellent agreement with the recent conjectures of den Nijs and of Nienhuis et al.