Question

How can I split the Klein-Gordon equation into first order ODEs?

Answer 1

The Klein Gordon eqution in conformal time without perturbations is:

enter image description here

I want to solve the equation numerically, but to do so I need to split it into 2 first order differential equations. What would it look like?

So far I have ψ′1=ψ2 and ψ′2=−2(a′/a)ψ2