arcsec.

Many researchers claimed that there is a good agreement between the theory and observation of the core radius. For example, Djorgovski and Meylan (1994) found that no observed cluster has the core radius smaller than 1% of the half-light radius, using the data compiled by Trager (1993), and argued this to be in good agreement with the model that assumes the binary-dominated core for PCC clusters (Vesperini and Chernoff 1994).

This apparently good agreement between the “observation” and “theory” is actually due to the fact that both of them overestimated the core size. On the observational side, High-resolution observations have shown that the real core size of the PCC clusters is significantly smaller than what is assumed in Djorgovski and Meylan (1994). Trager (1993) adopted the HWHM as the core size of PCC clusters. Since the HWHM has no relation to the real core radius of the PCC clusters, it is quite natural that observations with higher resolution obtained smaller core radii. On the theoretical side, our present result suggest that the typical size of the core in the gravothermal oscillation phase is significantly smaller than the previous claims.

Our result suggests that the typical size of the core 