content_image/423141.jpg content_image/423142.jpg content_image/423150.jpg
<img src='content_image/423141.jpg'>

cal temperatures. The error bars shown in this panel reflect the sample-to-sample fluctuations of the pseudo- critical temperatures. Again, the results obtained from the simultaneous fitting attempt T$_{c}$ = 3 . 4682(59) and ν = 0 . 996(8), as also shown in the figure, agree excel- lently with the estimates of panel (a), providing further evidence in favor of the accuracy of our numerical scheme and the strong universality hypothesis. Noteworthy that, if we fix the exponent ν to the exact value ν = 1 we get the most accurate estimates for the critical temperature to be 3 . 4663(16) and 3 . 4669(19) from the corresponding fittings of panels (a) and (b) of Fig. 5. 

Using now the above sample-to-sample fluctuations of 

<img src='content_image/423142.jpg'>

the pseudocritical temperatures and the theory of FSS in disordered systems as introduced by Aharony and Har- ris [73] and Wiseman and Domany [74], one may fur- ther examine the nature of the fixed point that controls the critical behavior of the disordered system. According to the theoretical predictions [73, 74], the pseudocritical temperatures T ∗ Z of the disordered system are distributed with a width δ [ T ∗ $_{Z}$]$_{av}$ , that scales with the system size as 

where n = d/ 2 or n = 1 /ν$_{r}$ , depending on whether the disordered system is controlled by the pure or the ran- dom fixed point, respectively. In panel (c) of Fig. 5 we plot these sample-to-sample fluctuations of the pseudo- critical temperature of the magnetic susceptibility. The solid line shows a very good power-law fitting giving the value 1 . 001(3) for the exponent n of the theory, which is in agreement with the case n = d/ 2, indicating that the random model is controlled by the pure fixed point. We should note here that analogous results to those dis- cussed here in panel (c) for the case of the site-diluted Ising model on the square lattice have been presented by 

<img src='content_image/423150.jpg'>

