Probing pre-inflationary anisotropy with directional variations in the
  gravitational wave background
  We perform a detailed analysis on a primordial gravitational-wave background
amplified during a Kasner-like pre-inflationary phase allowing for general
triaxial anisotropies. It is found that the predicted angular distribution map
of gravitational-wave intensity on large scales exhibits topologically
distinctive patterns according to the degree of the pre-inflationary
anisotropy, thereby serving as a potential probe for the pre-inflationary early
universe with future all-sky observations of gravitational waves. We also
derive an observational limit on the amplitude of such anisotropic
gravitational waves from the B-mode polarisation of the cosmic microwave
background.
