Star cluster disruption
  Star clusters are often used as tracers of major star formation events in
external galaxies as they can be studied up to much larger distances than
individual stars. It is vital to understand their evolution if they are used to
derive, for example, the star formation history of their host galaxy. More
specifically, we want to know how cluster lifetimes depend on their environment
and structural properties such as mass and radius. This review presents a
theoretical overview of the early evolution of star clusters and the consequent
long term survival chances. It is suggested that clusters forming with initial
densities of >10^4 Msun pc-3 survive the gas expulsion, or "infant mortality",
phase. At ~10 Myr they are bound and have densities of 10^{3+/-1} Msun pc-3.
After this time they are stable against expansion by stellar evolution,
encounters with giant molecular clouds and will most likely survive for another
Hubble time if they are in a moderate tidal field. Clusters with lower initial
densities (<100 Msun pc-3) will disperse into the field within a few 10s of
Myrs. Some discussion is provided on how extra galactic star cluster
populations and especially their age distributions can be used to gain insight
in disruption.
