Paper 4, Section I, A

Classical Dynamics
Part II, 2012

Consider a one-dimensional dynamical system with generalized coordinate and momentum (q,p)(q, p).

(a) Define the Poisson bracket {f,g}\{f, g\} of two functions f(q,p,t)f(q, p, t) and g(q,p,t)g(q, p, t).

(b) Find the Poisson brackets {q,q},{p,p}\{q, q\},\{p, p\} and {q,p}\{q, p\}.

(c) Assuming Hamilton's equations of motion prove that

dfdt={f,H}+ft\frac{d f}{d t}=\{f, H\}+\frac{\partial f}{\partial t}

(d) State the condition for a transformation (q,p)(Q,P)(q, p) \rightarrow(Q, P) to be canonical in terms of the Poisson brackets found in (b). Use this to determine whether or not the following transformations are canonical:

(i) Q=sinq,P=pacosqQ=\sin q, P=\frac{p-a}{\cos q},

(ii) Q=cosq,P=pasinqQ=\cos q, P=\frac{p-a}{\sin q},

where aa is constant.