A common parameterization is to assume the equation of state parameter w = p/rho = constant. As of April 2003 CAMB includes this parameterization by default. It assumes that Omega_Lambda is Omega_Quintessence, with constant equation of state w (i.e. you can't have Lambda and quintessence).

There is also a more general quintessence module that lets you specific a single scalar field potential. It will need customization for different potentials, and changes to the way initial conditions are set if trying to use a tracker model. You can download the modified equations module for CAMB. It is not very well tested.

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