Canonical phase-space transformations
A canonical transformation changes phase-space coordinates and the Hamiltonian while preserving Hamilton's description of the same physical trajectories.
Key knowledge
A canonical transformation changes phase-space coordinates and the Hamiltonian while preserving Hamilton's description of the same physical trajectories. A time-independent canonical transformation preserves the fundamental Poisson brackets and transforms H by composition; a time-dependent transformation also changes H by a time-dependent correction.
Values and equations
{Q_i,Q_j}=0; {P_i,P_j}=0; {Q_i,P_j}=δ_ij
- Q_i,P_i
- New canonical coordinates/momenta; product unit J s
- {…}
- Old-coordinate canonical Poisson bracket
- δ_ij
- Kronecker delta
- i,j
- Degree-of-freedom indices
Conditions and scope
- Smooth invertible canonical phase-space change in a regular finite-dimensional Hamiltonian domain.
- An arbitrary invertible phase-space map is not canonical. Preserving volume alone is weaker than preserving the full canonical/symplectic structure.
Sources · 1
References
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Evidence and review
Structure and Interpretation of Classical Mechanics: Canonical transformations: Chapter opening and §5.1 equations 5.6–5.12: transformed coordinates/momenta/H and time-dependent correction; Poisson/symplectic characterization in §5.2.
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