title: 'Post-Collapse evolution of globular clusters'
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Introduction
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A number of globular clusters appear to have undergone core collapse ([@Cohn1984], [@Hut1992]). Djorgovski and King (1986) showed that 15% of galactic globular clusters have unresolved density cusps. Recent observations with HST have demonstrated that some of these clusters have the core sizes smaller than 0.03 arcsec, which is as far as one can go with present technique ($e.g.$, [@Sosin1995], [@Yanny1994]).

The theoretical study of the evolution after the core collapse was pioneered by Henon (1975), who incorporated the energy production by binaries into his Monte-Carlo calculation. He found that the whole cluster expanded homologously in the thermal timescale. Similar results were obtained by gaseous models and Fokker-Planck calculations.

Sugimoto and Bettwieser (1983, Bettwieser and Sugimoto 1984) found that the post-collapse expansion is unstable if the energy production is inefficient. In the unstable case, the central density showed an oscillation with a large amplitude. They called this oscillation gravothermal oscillation. They modelled the post-collapse evolution of globular clusters using a conducting gas sphere with artificial energy production. The efficiency of the energy production is related to the total number of particles $N$, and for large $N$ efficiency is small. Thus, their 