Few body interactions near central massive objects

The configuration of a central massive object interacting gravitationally with much lighter objects
around it (so called near Keplerian system) appears on many astrophysical scales. At the largest
scales massive black holes (MBHs; thought to exist in most if not all galactic nuclei,) and the stellar
systems around them, exemplify such systems. Close interactions of stars with MBHs lead in many
cases to catastrophic outcomes; a star or a binary star could be disrupted following a close encounter
with the MBH; a compact object, such as a stellar black hole, neutron stars or a white dwarf may inspiral
to the MBH, through gravitational wave (GW) emission. In this Thesis the dynamics of stars
and their close interactions near MBHs are studied. We explore several directions including the
effects of massive perturbers such as giant molecular clouds on the dynamics of stars near MBHs; the
close interaction of stars and binary stars with MBHs and their rates; and the origin and dynamical
evolution of hypervelocity stars ejected by MBHs. We show that massive perturbers can accelerate
relaxation processes in Galactic nuclei by orders of magnitude. Scattering of stars by such perturbers
can explain the origin of the young stars observed very close to the MBH in the Galactic center, as
well as the origin of hypervelocity stars observed in the Galactic halo. Massive perturbers could also
have a major role in the coalescence of binary MBHs and induce their merger in short times, leading
to their inspiral
through GW emission, likely to be observable with future space programs. We also
obtained strong constraints on the origin of hypervelocity stars, and found a novel method to use them
as probes of the Galactic potential at large scales.