Hamilton's equations for a Hamiltonian H(q,p) w.r.t. to a standard symplectic from ω=dq∧dp are ˙q=∂Hp,˙p=−∂Hq
How do Hamilton's equations write w.r.t. a nonstandard symplectic form F(q,p)dq∧dp, where F(q,p) is some smooth function?
Answer
More generally, let there be given a Poisson manifold (M,π), where π = 12πIJ∂∂zI∧∂∂zJ
is a Poisson bi-vector, and {f,g}PB = ∂f∂zJπIJ∂g∂zJis the corresponding Poisson bracket. Let the Hamiltonian H be a globally defined function on M. Then Hamilton's equations read ˙zI = {zI,H}PB,i.e. time-evolution is given by (minus) the Hamiltonian vector field XH = {H,⋅}PB.If the Poisson structure is invertible, then M is a symplectic manifold with symplectic 2-form ω = 12ωIJ dzI∧dzJ,
where ωIJ is the inverse matrix: πIJωJK = δIK.In canonical/Darboux coordinates (z1,…,z2n) = (q1,…,qn,p1,…,pn),
the above construction reduces to the standard Poisson bi-vector π = ∂∂qi∧∂∂pi,and the standard symplectic 2-form ω = dpi∧dqi.
No comments:
Post a Comment