Bispectrum-window convolution via Hankel transform
  We present a method to perform the exact convolution of the model prediction
for bispectrum multipoles in redshift space with the survey window function. We
extend a widely applied method for the power spectrum convolution to the
bispectrum, taking advantage of a 2D-FFTlog algorithm. As a preliminary test of
its accuracy, we consider the toy model of a spherical window function in real
space. This setup provides an analytical evaluation of the 3-point function of
the window, and therefore it allows to isolate and quantify possible systematic
errors of the method. We find that our implementation of the convolution in
terms of a mixing matrix shows differences at the percent level in comparison
to the measurements from a very large set of mock halo catalogs. It is also
able to recover unbiased constraints on halo bias parameters in a likelihood
analysis of a set of numerical simulations with a total volume of $100\, h^{-3}
\, {\rm Gpc}^3$. For the level of accuracy required by these tests, the
multiplication with the mixing matrix is performed in the time of one second or
less.
