### Equations in Quint module in quintessence equations file for CAMB

Posted:

**January 30 2020**Hi all,

I am trying to modify the equation file for quintessence for CAMB provided at https://camb.info/equations_quint.f90.

In
which is consistent with the standard definition [math] (eq. 6.5 in Theory of cosmological perturbations ) upto a overall factor of [math] where

But later in the file in
which is supposed to produce the value of [math], which should be [math] multiplied by an overall factor.

But considering the definition this doesn't seem to be consistent with the definition since
is equivalent to [math] which cannot be same as the definition of $\rho_{\phi}$ or $\Omega_{\phi}$ irrespective of any overall factor.

I am not sure if it is an error in the code, or if I am missing something.

Best

Joseph

I am trying to modify the equation file for quintessence for CAMB provided at https://camb.info/equations_quint.f90.

In

**subroutine EvolveBackground**, the energy density of the scalar field is defined asCode: Select all

`tmp=a2*(0.5d0*phidot**2 + a2*Vofphi(phi,0))`

*prime*denotes the derivative with respect to the conformal time.But later in the file in

**function Quint_GetOmegaFromInitial**, it is given thatCode: Select all

`Quint_GetOmegaFromInitial=(0.5d0*y(2)**2 + Vofphi(y(1),0))/(3*adot**2)`

But considering the definition

Code: Select all

`y(2)=phidot*astart**2`

Code: Select all

`tmp=a2*(0.5d0*phidot**2 + a2*Vofphi(phi,0))`

Code: Select all

`(0.5d0*y(2)**2 + Vofphi(y(1),0))`

I am not sure if it is an error in the code, or if I am missing something.

Best

Joseph