### CAMB slows a lot when adding a scalar field with heavy mass

Posted:

**July 09 2019**Dear all

Hello, I'm trying to implement some new exotic physics in CAMB. the new physics in my model is basically from a new massive scalar field and its equation is just a plain KG equation:

[math].

The field [math] affects evolution of matter density perturbation and perturbation of expansion rate [math] and [math] corresponds to GR. The lower value contributes to ISW effect and increase low [math] value of [math]. (it's similar to normal quintessence but it does not affects background evolution.)

The problem is when I increase the value of [math] the computation of CAMB slows a lot. (for low value like [math] it only takes less than 2 seconds but for [math] it takes more than 10 minutes.) I added the new field as the same way for quintessence. There is no error in output values.

How can I speed up the code to use CosmoMC in my personal computer? Or is there any fast approximation scheme for solving KG equation?

I use CAMB files in CosmoMC master branch(downloaded at 19/07/01) and my CPU is AMD ryzen 7 2700X (8 core).

Thank you.

Hello, I'm trying to implement some new exotic physics in CAMB. the new physics in my model is basically from a new massive scalar field and its equation is just a plain KG equation:

[math].

The field [math] affects evolution of matter density perturbation and perturbation of expansion rate [math] and [math] corresponds to GR. The lower value contributes to ISW effect and increase low [math] value of [math]. (it's similar to normal quintessence but it does not affects background evolution.)

The problem is when I increase the value of [math] the computation of CAMB slows a lot. (for low value like [math] it only takes less than 2 seconds but for [math] it takes more than 10 minutes.) I added the new field as the same way for quintessence. There is no error in output values.

How can I speed up the code to use CosmoMC in my personal computer? Or is there any fast approximation scheme for solving KG equation?

I use CAMB files in CosmoMC master branch(downloaded at 19/07/01) and my CPU is AMD ryzen 7 2700X (8 core).

Thank you.