In a recent paper (Hall 2008 J. Phys. A: Math. Gen. 41 255301), I made several critical remarks on a ‘Hermitian time operator’ proposed by Galapon (2002 Proc. R. Soc. A 458 2671). Galapon has correctly pointed out that remarks pertaining to ‘denseness’ of the commutator domain are wrong (Galapon 2008 J. Phys. A: Math. Theor. 42 018001). However, the other remarks still apply, and it is further noted that a given quantum system can be a member of this domain only at a set of times of total measure zero.
Monte Carlo simulations on a variety of finite 2D percolating systems at criticality suggest that the excess number of clusters over the bulk value nc is a universal quantity, dependent upon the system shape but independent of the lattice and percolation type. Values of nc are found to high accuracy, and for bond percolation are in accord with the theoretical predictions of Temperley and Lieb [Proc. R. Soc. London A 322, 251 (1971)], and Baxter, Temperley, and Ashley [Proc. R. Soc. London A 358, 535 (1978)], whose results we have evaluated explicitly in terms of simple algebraic numbers. Fluctuations are also studied.