A novel probe of bubble size statistics and time scales of the epoch of
  reionization using the contour Minkowski Tensor
  We employ the rank-2 {\em contour} Minkowski Tensor in two dimensions to
probe length and time scales of ionized bubbles during the epoch of
reionization. We demonstrate that the eigenvalues of this tensor provide
excellent probes of the distribution of the sizes of ionized bubbles, and from
it the characteristic bubble sizes, at different redshifts. We show that
ionized bubbles are not circular, and hence not spherical in three dimensions,
as is often assumed for simplified analytic arguments. We quantify their shape
anisotropy by using the ratio of the two eigenvalues. The shape parameter
provides the characteristic time epochs when bubble mergers begin and end. Our
method will be very useful to reconstruct the reionization history using data
of the brightness temperature field.
