The impact of primordial binary on the dynamical evolution of
  intermediate massive star clusters
  Observations found that star clusters contain a large fraction of binaries.
Tight binaries are an important heating source that influences the long-term
dynamical evolution of star clusters. However, due to the limitation of
$N$-body tool, previous theoretical modelling for globular clusters (GCs) by
using direct $N$-body simulations have not investigated how a large fraction of
primordial binaries affect their long-term evolution. In this work, by using
the high-performance $N$-body code, PeTar, we carry out star-by-star models for
intermediate massive GCs ($N=100000$) with the primordial binary fraction
varying from 0 to 1. We find that when a stellar-mass black hole (BH) subsystem
exists, the structural evolution of GCs (core and half-mass radii) only depends
on the properties of massive primordial binaries, because they affect the
number of BH binaries (BBHs), which dominate the binary heating process.
Low-mass binaries including double white dwarf binaries (BWDs) have almost no
influence on the dynamics. Meanwhile, only gravitational wave (GW) mergers from
BBHs are strongly affected by dynamical interactions, while low-mass mergers
from BWDs show no difference in the isolated environment (field) and in GCs.
Low-mass binaries become important only after most BHs escape and the core
collapse of light stars occurs. Our result suggests that for $N$-body modelling
of GCs with a black hole subsystem dominating binary heating, it is not
necessary to include low-mass binaries. These binaries can be studied
separately by using standalone binary stellar evolution codes. This way can
significantly reduce the computing cost.
