CAMB:Isocurvature perturbations

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Akhilesh Nautiyal(akhi)
Posts: 72
Joined: June 13 2007
Affiliation: Malaviya National Institute of Technology Jaipur

CAMB:Isocurvature perturbations

Post by Akhilesh Nautiyal(akhi) » July 19 2007

Hi,

I am running CAMB to find Cls usnig CDM isocuvature
perturbations.
I would like to know how to get Cls with correlated aidiabatic-isocurvature perturbations. I think CAMB gives cls using aidiabatic and isocruvarture perturbations seperatly.
Can any one help me in getting correlated aidiabatic-isocurvature cls?

Thanks,
Akhilesh


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Antony Lewis
Posts: 1941
Joined: September 23 2004
Affiliation: University of Sussex
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Re: CAMB:Isocurvature perturbations

Post by Antony Lewis » July 19 2007

CAMB can get individual spectra or totally (anti-)correlated spectra with the same initial power spectrum.

To get the correlated ones set

Code: Select all

initial_condition   = 0
and change

Code: Select all

initial_vector = -1 0 0 0 0
to whatever weighting of the modes you like. To get partially correlated spectra you'd need to run CAMB a few times with different inputs and combine results.

Akhilesh Nautiyal(akhi)
Posts: 72
Joined: June 13 2007
Affiliation: Malaviya National Institute of Technology Jaipur

CAMB:Isocurvature perturbations

Post by Akhilesh Nautiyal(akhi) » July 19 2007

Dear Mr. A. Lewis

I thank you for your kind help. I tried with taking initial condition=0. But I could'nt
understand the meaning of "initial_vector = -1 0 0 0 0". There are five numbers in this line.
Would you please explain me about each number?
Suppose I want to get total Cls as

[tex]Cl^{total}=(1-\alpha) Cl^{AA}+\alpha Cl^{iso}+2\beta \sqrt{\alpha (1-\alpha)}Cl^{corr}[/tex]

taking [tex]\alpha[/tex] and [tex]\beta[/tex] as 0.1 and 0.2 respectivily.
Then what numbers I have to put in initial_vector = -1 0 0 0 0?
I have taken above formula from Bean, Dunkley and Pierpaoli Phys. Rev .D 74, 063503 (2006).


Looking forward for your help.

Thanking you,
Sincerely,
Akhilesh

Antony Lewis
Posts: 1941
Joined: September 23 2004
Affiliation: University of Sussex
Contact:

Re: CAMB:Isocurvature perturbations

Post by Antony Lewis » July 19 2007

The five numbers are the initial amplitudes of the different isocurvature modes (see comment in the .ini file). For definitions see the notes.

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