Physical interactions between stars.

Physical arguments are presented to show that two-body, tidal-capture binaries should form in abundance during the evolution of globular clusters by the time that core collapse begins. Interactions amongst these binaries and with core single stars will cause ejections from the cluster which pump energy into the system producing a bounce and re-expansion. Detailed numerical Fokker-Planck evolutionary calculations presented here confirm this scenario and indicate that this process is likely to be the dominant energy input for most clusters. During the reexpansion phase r (core) is proportional to the cube of t, and r(half) is proportional to t exp 2/3, with the core containing several hundred very close binary star systems.