CAMB : primordial power spectrum

[Susana Landau]

Hi:

According to the coments in the file power_tilt.f90 the primordial power spectrum to be entered in camb is the the power spectrum of the conserved curvature perturbation given by
[tex] -\chi = \Phi +\frac{2}{3} \Omega^{-1} \frac{H^{-1}\Phi ' - \Psi}{1+\omega}[/tex]

However, in the paper by Ma and Bertschinger arXiv:astro-ph/9506072
" Cosmological Perturbation Theory in the Synchronous and Conformal Newtonian Gauges"

the primordial power spectrum to be computed in the power spectrum of the variable \Psi

Finally, at the end of inflation

-\chi = 2/3 \Psi

Is this the reason for the difference in CAMB and the paper by Ma and Bertschinger? or in other words: the power spectrum of what variable should be entered in camb?

thanks in advanced for the help

regards

Susana Landau

[Antony Lewis]

Use what it says in power_tilt: the comoving curvature perturbation is conserved for super-horizon adiabatic perturbations. The potential is not conserved if the equation of state changes (e.g. the old result assumes matter domination).