Black hole mergers from an evolving population of globular clusters
  The high rate of black hole (BH) mergers detected by LIGO/Virgo opened
questions on their astrophysical origin. One possibility is the dynamical
channel, in which binary formation and hardening is catalyzed by dynamical
encounters in globular clusters (GCs). Previous studies have shown that the BH
merger rate from the present day GC density in the Universe is lower than the
observed rate. In this \textit{Letter}, we study the BH merger rate by
accounting for the first time for the evolution of GCs within their host
galaxies. The mass in GCs was initially $\sim 8\times$ higher, which decreased
to its present value due to evaporation and tidal disruption. Many BH binaries
that were ejected long before their merger, originated in GCs that no longer
exist. We find that the comoving merger rate in the dynamical channel from GCs
varies between $18$ to $35\,{\rm Gpc}^{-3}\,{\rm yr}^{-1}$ between redshift
$z=0.5$ to $2$, and the total rate is $1$, $5$, $24$ events per day within
$z=0.5$, $1$, and $2$, respectively. The cosmic evolution and disruption of GCs
systematically increases the present-day merger rate by a factor $\sim 2$
relative to isolated clusters. Gravitational wave detector networks offer an
unique observational probe of the initial number of GC populations and their
subsequent evolution across cosmic time.
