### CAMB: scale factor and adotrad

Posted:

**December 05 2018**Hi.

I want to know reference about exact relation between scale factor and conformal time.

In subroutine initial, a=tau*adotrad*(1+omtau/4).

In CAMB note 12p, regular initial condition series solution S.

In this solution, there is a sentense ‘Following [20]’, but [20] is not found.

What is ‘adotrad’ in module.f90 meaning?

I think ‘adotrad’ is H0*dsqrt(omega_R0), but it’s different value from adotrad.

And, does anyone know reference for scale factor S?

Any help would be appreciated.

I want to know reference about exact relation between scale factor and conformal time.

In subroutine initial, a=tau*adotrad*(1+omtau/4).

In CAMB note 12p, regular initial condition series solution S.

In this solution, there is a sentense ‘Following [20]’, but [20] is not found.

What is ‘adotrad’ in module.f90 meaning?

I think ‘adotrad’ is H0*dsqrt(omega_R0), but it’s different value from adotrad.

And, does anyone know reference for scale factor S?

Any help would be appreciated.