Black hole mergers and blue stragglers from hierarchical triples formed
  in globular clusters
  Hierarchical triple-star systems are expected to form frequently via close
binary-binary encounters in the dense cores of globular clusters. In a
sufficiently inclined triple, gravitational interactions between the inner and
outer binary can cause large-amplitude oscillations in the eccentricity of the
inner orbit ("Lidov-Kozai cycles"), which can lead to a collision and merger of
the two inner components. In this paper we use Monte Carlo models of dense star
clusters to identify all triple systems formed dynamically and we compute their
evolution using a highly accurate three-body integrator which incorporates
relativistic and tidal effects. We find that a large fraction of these triples
evolve through a non-secular dynamical phase which can drive the inner binary
to higher eccentricities than predicted by the standard secular perturbation
theory (even including octupole-order terms). We place constraints on the
importance of Lidov-Kozai-induced mergers for producing: (i) gravitational wave
sources detectable by Advanced LIGO (aLIGO), for triples with an inner pair of
stellar black holes; and (ii) blue straggler stars, for triples with
main-sequence-star components. We find a realistic aLIGO detection rate of
black hole mergers due to the Lidov-Kozai mechanism of 1yr^-1, with about 20%
of these having a finite eccentricity when they first chirp into the aLIGO
frequency band. While rare, these events are likely to dominate among eccentric
compact object inspirals that are potentially detectable by aLIGO. For blue
stragglers, we find that the Lidov-Kozai mechanism can contribute only up to
~10% of their total numbers in globular clusters.
