SERIES EXPANSIONS OF THE PERCOLATION PROBABILITY ON THE DIRECTED TRIANGULAR LATTICE

We have derived long-series expansions of the percolation probability for site, bond and site-bond percolation on the directed triangular la ttice. For the bond problem we have extended the series from order 12 to 51 and for the site problem from order 12 to 35. For the site-bond problem, which has not been studied before, we have derived the series to order 32. Our estimates of the critical exponent beta are in full agreement with results for similar problems on the square lattice, con firming expectations of universality. For the critical probability and exponent we find in the site case: q(c) = 0.404 352 8 +/- 0.000 001 0 and beta = 0.276 45 +/- 0.000 10; in the bond case: q(c) = 0.521 98 /- 0.000 01 and beta = 0.2769 +/- 0.0010; and in the site-bond case: q (c) = 0.264 173 +/- 0.000 003 and beta = 0.2766 +/- 0.0003. In additio n we have obtained accurate estimates for the critical amplitudes. In all cases we find that the leading correction to scaling term is analy tic, i.e. the confluent exponent Delta = 1.