output spectra - info and user-control

[humnaawan]

Is there a place where one can find info re what's outputted exactly? Currently, I see the output dictionary having spectra for clTT, clEE, clBB, clTE, clPP, clPT, clPE. What is "P" here?

Also,

• can one specify e.g. getting just a subset of combinations?
• is there are a reason clEB is missing?

[samueldmcdermott]

"P" represents the gravitational potential which is often written with the greek letter Φ (transliterated Phi). You can certainly omit some if you don't care about them. The E-B cross-correlation is expected to be exactly zero in a parity-conserving universe, which is a common expectation (and, at the very least, parity is not badly broken, so this likely to be small)

[humnaawan]

@samueldmcdermott can you please say how I can drop some of the correlations from the outputs? I know I can drop things from the output dictionary but is there an option to not return specific spectra at all?

The E-B cross-correlation is expected to be exactly zero in a parity-conserving universe, which is a common expectation (and, at the very least, parity is not badly broken, so this likely to be small)

sure, but is there an option for me to get this correlation?

[samueldmcdermott]

@humnaawan -- the E-B cross-correlation is exactly zero in all cosmological perturbation theory codes that I know of. If there's a reason that you need a placeholder for it, I suppose you can use np.zeros_like() wrapping some other spectrum that you have.

As for not returning specific spectra -- that's not currently possible. If that's valuable (for space or memory reasons) I think it shouldn't be too hard to implement, but it might not save much time given my understanding of CAMB (one single call gives all of TT, EE, BB, TE, and another call gives PP, PT, PE, and I think the second one is fast given how CAMB calculates that). But if you think that functionality seems valuable, let me know what options you'd like (eg, specify all the ones you want? or three options like TEB, Phi, all?) and I can make it happen

[samueldmcdermott]

closed by #87 and #88