NumCosmoXcorKernelCluster

Base class for cluster kernels in cross-correlations.

This is a placeholder base class for cluster kernels. The full implementation of a cluster kernel would potentially involve integration over halo mass function:

\begin{equation} K_\alpha(z,k) = \frac{dV}{dz}(z) \left[ \int dM \, b(M,z) \, \frac{dn}{dM}(M,z) \, S_\alpha(M,z) \, p(M,z) \right] \sqrt{P(k,z)} \end{equation}

where: - $\frac{dV}{dz}$ is the comoving volume element per steradian, - $\frac{dn}{dM}(M,z)$ is the halo mass function, - $b(M,z)$ is the halo bias, - $S_\alpha(M,z)$ is the selection function of bin $\alpha$, - $p(M,z)$ is the catalog purity, - $P(k,z)$ is the matter power spectrum.

Different implementations will provide different approximations or methods for computing this kernel.