Paper 2, Section I, E

Classical Dynamics | Part II, 2019

(a) State Hamilton's equations for a system with nn degrees of freedom and HamiltonianH(q,p,t)\operatorname{nian} H(\mathbf{q}, \mathbf{p}, t), where (q,p)=(q1,,qn,p1,,pn)(\mathbf{q}, \mathbf{p})=\left(q_{1}, \ldots, q_{n}, p_{1}, \ldots, p_{n}\right) are canonical phase-space variables.

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

(c) State the canonical commutation relations of the variables q\mathbf{q} and p\mathbf{p}.

(d) Show that the time-evolution of any function f(q,p,t)f(\mathbf{q}, \mathbf{p}, t) is given by

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

(e) Show further that the Poisson bracket of any two conserved quantities is also a conserved quantity.

[You may assume the Jacobi identity,

{f,{g,h}}+{g,{h,f}}+{h,{f,g}}=0.]\{f,\{g, h\}\}+\{g,\{h, f\}\}+\{h,\{f, g\}\}=0 .]

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