Upper Limits on the Stochastic Gravitational-Wave Background from
  Advanced LIGO's First Observing Run
  A wide variety of astrophysical and cosmological sources are expected to
contribute to a stochastic gravitational-wave background. Following the
observations of GW150914 and GW151226, the rate and mass of coalescing binary
black holes appear to be greater than many previous expectations. As a result,
the stochastic background from unresolved compact binary coalescences is
expected to be particularly loud. We perform a search for the isotropic
stochastic gravitational-wave background using data from Advanced LIGO's first
observing run. The data display no evidence of a stochastic gravitational-wave
signal. We constrain the dimensionless energy density of gravitational waves to
be $\Omega_0<1.7\times 10^{-7}$ with 95% confidence, assuming a flat energy
density spectrum in the most sensitive part of the LIGO band (20-86 Hz). This
is a factor of ~33 times more sensitive than previous measurements. We also
constrain arbitrary power-law spectra. Finally, we investigate the implications
of this search for the background of binary black holes using an astrophysical
model for the background.
