CosmoCoffee Forum Index CosmoCoffee

 
 FAQFAQ   SearchSearch  MemberlistSmartFeed   MemberlistMemberlist    RegisterRegister 
   ProfileProfile   Log inLog in 
Arxiv New Filter | Bookmarks & clubs | Arxiv ref/author:

Large Scale value of $\delta_g/4+2\Phi$
 
Post new topic   Reply to topic    CosmoCoffee Forum Index -> Computers and software
View previous topic :: View next topic  
Author Message
Muhammad Junaid



Joined: 05 Jan 2017
Posts: 7
Affiliation: University of Alberta

PostPosted: May 16 2017  Reply with quote

Hi, I am plotting the value of δg / 4 + 2Φ from the transfer function output file. If you look at its value at large scales (k = 6.96268e − 06) it's value come out to be ~0.9 rather than the Saachs Wolfe factor of 1 / 5 or 1 / 3. So, I wanted wanted to ask where I am going wrong with my understanding.
Thanks,
M.J.
Back to top
View user's profile  
Antony Lewis



Joined: 23 Sep 2004
Posts: 1278
Affiliation: University of Sussex

PostPosted: May 16 2017  Reply with quote

Firstly make sure you are using Newtonian gauge δg not the synchronous gauge one output by default. Secondly there are corrections from neutrino anisotropic stress and recombination not being exactly matter dominated.
Back to top
View user's profile [ Hidden ] Visit poster's website
Muhammad Junaid



Joined: 05 Jan 2017
Posts: 7
Affiliation: University of Alberta

PostPosted: May 16 2017  Reply with quote

So how can I get the transfer functions in Newtonian gauge or gauges other then synchronous gauge.
Back to top
View user's profile  
Antony Lewis



Joined: 23 Sep 2004
Posts: 1278
Affiliation: University of Sussex

PostPosted: May 18 2017  Reply with quote

There's no direct way to get that, you'd have to construct the corresponding gauge invariant combination of synchronous gauge density and shear (which you could infer from the output synchronous gauge density, Newtonian-gauge CDM velocity and the Hubble parameter, using relations described in the CAMB notes p22).
Back to top
View user's profile [ Hidden ] Visit poster's website
Display posts from previous:   
Post new topic   Reply to topic    CosmoCoffee Forum Index -> Computers and software All times are GMT + 5 Hours
Page 1 of 1

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum


Powered by phpBB © 2001, 2005 phpBB Group. Sponsored by WordWeb online dictionary and dictionary software.