An observational signal of the void shape correlation and its link to
  the cosmic web
  The shapes of cosmic voids are prone to distortions by the external tidal
forces since their low-densities imply a lower internal resistance. This
susceptibility of the void shapes to the tidal distortions makes them useful as
an indicator of the large-scale tidal and density fields, despite the practical
difficulty in defining them. Using the void catalog constructed by Pan et al.
(2012) from the Seventh Data Release of the Sloan Digital Sky Survey (SDSS
DR7), we detect a clear 4 sigma signal of spatial correlations of the void
shapes on the scale of 20 Mpc/h and show that the signal is robust against the
projection of the void shapes onto the plane of sky. By constructing a simple
analytic model for the void shape correlation, within the framework of tidal
torque theory, we demonstrate that the void shape correlation function scales
linearly with the two-point correlation function of the linear density field.
We also find a direct observational evidence for the cross-correlation of the
void shapes with the large-scale velocity shear field that was linearly
reconstructed by Lee et al. (2014) from the SDSS DR7. We discuss the
possibility of using the void shape correlation function to break the
degeneracy between the density parameter and the power spectrum amplitude and
to independently constrain the neutrino mass as well.
