Symplectic integration and modified energy
Research context
research method · conditional · As of 2026-10-10
For separable H=pᵀM⁻¹p/2+V(q), fixed-step kick–drift–kick Verlet is second order, reversible and symplectic.
Key knowledge
For separable H=pᵀM⁻¹p/2+V(q), fixed-step kick–drift–kick Verlet is second order, reversible and symplectic. It generally preserves neither the exact Hamiltonian nor every observable exactly. Backward-error analysis explains near-conservation of a modified energy on suitable long intervals when smoothness, step-size and bounded-trajectory hypotheses hold.
Values and equations
p_(n+½)=p_n−(h/2)∇V(q_n); q_(n+1)=q_n+hM⁻¹p_(n+½); p_(n+1)=p_(n+½)−(h/2)∇V(q_(n+1))
- q
- Position vector m
- p
- Momentum vector kg m s⁻¹
- M
- Mass matrix kg
- V
- Potential energy J
- h
- Fixed time step s
Conditions and scope
- Constant positive mass matrix, smooth potential and fixed time step h. Naive state-dependent step adaptation may destroy symplecticity.
- Resolve the fastest relevant oscillation, enforce constraint algorithms where needed, and compare h versus h/2 trajectories and energy errors. Symplecticity alone is not convergence.
Sources · 1
References
Sources retain their recorded scope. A source link alone does not establish verification of every statement.
Evidence and review
Inspected §§1.2, 2, 4–6: splitting, symplecticity, modified Hamiltonians, non-resonance and constraint algorithms; source check dated 2026-10-10. Scope is limited to the cited statements, equations and assumptions, not the whole publication.
2026-10-10 · Author source inspection of the displayed claim, model assumptions and equations; independent exact-content and branch-inventory review is a separate gate. Contemporary status is a dated snapshot, not a promise of ongoing monitoring.
Entry details
Permanent link to this entry ↗- Record identity
- research-physics-symplectic-verlet
- Revision
- research.1
- Structured reference record
- Postgraduate & research reference