SERIES EXPANSIONS OF THE PERCOLATION PROBABILITY FOR DIRECTED SQUARE AND HONEYCOMB LATTICES

We have derived long series expansions of the percolation probability fbr site anti bond percolation on directed square and honeycomb lattic es. For the square bond problem we have extended the series from 41 te rms to 54, for the square site problem from 16 terms to 37, and for th e honeycomb bond problem from 13 terms to 36. Analysis of the series c learly shows that the critical exponent beta is the same fdr all the p roblems, confirming expectations of universality. For the critical pro bability and exponent we find in the square bond case, q(c) = -0.35529 94 +/- 0.0000010, beta = 0.27643 +/- 0.00010; in the square site case q(c) = 0.294515 +/- 0.000005, beta = 0.2763 +/- 0.0003; and in the hon eycomb bond case q(c) = 0.177143 +/- 0.000002, beta = 0.2763 +/- 0.000 2. In addition we have obtained accurate estimates for the critical am plitudes. In all cases we find that the leading correction to scaling term is analytic, i.e. the confluent exponent Delta = 1.