- #1
HashKetchum
- 6
- 0
Hello, I am having trouble deriving the equation of motion for the quintessence field.
The equation of motion which I am meant to get at the end point is: (with ' denoting derivative w.r.t time)
φ'' + 3Hφ' + dV/dφ = 0
Using the inflaton lagrangian:
(although with a generic potential V(φ) as opposed to m2φ^2.
with the euler-lagrange equation. However the best I have managed to achieve through this is:
φ'' + dV/dφ + (1/2)(φ')^2 + (H^3)φ'= 0
I effectively have the potential term and the φ'' term correct but the φ' terms are clearly wrong. I am unsure how I would ever get 3H as the prefix for the φ' term as I always get (a'/a)^3 which = H^3.
There is a lot of information online but it all seems to state that you just use the lagrangian with the euler-lagrange equations and get the equation of motion out but nothing has the full derivation!
Thank you for any help!
The equation of motion which I am meant to get at the end point is: (with ' denoting derivative w.r.t time)
φ'' + 3Hφ' + dV/dφ = 0
Using the inflaton lagrangian:
with the euler-lagrange equation. However the best I have managed to achieve through this is:
φ'' + dV/dφ + (1/2)(φ')^2 + (H^3)φ'= 0
I effectively have the potential term and the φ'' term correct but the φ' terms are clearly wrong. I am unsure how I would ever get 3H as the prefix for the φ' term as I always get (a'/a)^3 which = H^3.
There is a lot of information online but it all seems to state that you just use the lagrangian with the euler-lagrange equations and get the equation of motion out but nothing has the full derivation!
Thank you for any help!