wale.CovarianceMatrix module

wale.CovarianceMatrix.get_covariance(cosmo, z, variability, numberofrealisations)

Compute the nonlinear matter power spectrum P(k) and optionally its covariance using halo model trispectrum contributions.

If variability is enabled, the function uses the halo model (via pyccl) to compute the connected non-Gaussian trispectrum and generate power spectrum realizations by sampling from a multivariate Gaussian distribution.

Parameters:

• cosmo (Cosmology_function) – A Cosmology_function object that wraps pyccl and includes nonlinear P(k) access, k-grid, and other cosmological parameters.

• z (array_like) – Array of redshift values at which the power spectrum is evaluated.

• variability (bool) – Whether to compute and include non-Gaussian covariance (trispectrum) and draw realizations of P(k) using a halo model.

• numberofrealisations (int) – Number of mock realizations to draw for each redshift (if variability=True).

Returns:

• if variability is True –

  cov_dictdict

  Dictionary mapping redshift z to full covariance matrix C(k, k’).

  pk_samples_dictdict

  Dictionary mapping redshift z to an array of shape (N, nk) containing N sampled realizations of P(k).

  pk_dictdict

  Dictionary mapping redshift z to the mean nonlinear P(k) at that redshift.

• else –

  pk_dictdict

  Dictionary mapping redshift z to the mean nonlinear P(k) at that redshift.