SSC for g-g lensing and galaxy clustering using DarkEmulator

[RyoTerasawa]

I implemented the functions to calculate galaxy-matter and galaxy-auto power spectrum responses to the super-survey modes, which are responsible for super sample covariance. The halo statistics (halo-matter/halo-auto power spectrum, mass function) are calculated by DarkEmulator. We approximate the halo-matter/halo-auto power spectrum growth response to super-survey modes by its growth response to the Hubble parameter, which is calculated using DarkEmulator. Changes are mostly in darkemulator.py, which I created. In darkemulator.py, the main functions are

• darkemu_Pgm_Tk3D_SSC: returns a class:~pyccl.tk3d.Tk3D object containing the super-sample covariance trispectrum between galaxy-matter power spectra.

• darkemu_Pgm_resp: calculates galaxy-matter power spectrum responses to the super-survey modes.

• darkemu_Pgg_resp_zresp/darkemu_Pgg_resp_Asresp: calculates galaxy-auto power spectrum responses to the super-survey modes.

[RyoTerasawa]

The changes in this PR is now included in https://github.com/LSSTDESC/CCL/pull/1134