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Adiabatic invariance of the action of a slowly varying one-frequency model: an order- drift bound on the time scale
Adiabatic invariance of the action coordinate of a declared hyperregular potential presentation of the framework's force branch when the model carries a slow real parameter: if in a one-degree-of-freedom radian action-angle chart the branch Hamiltonian is with nonvanishing frequency and the parameter runs as , then along every model solution that stays in the compact chart region the action changes by at most the displayed order- bound on . The statement uses a dimensionless slow parameter, an inverse-time slow rate, energy-dimension h and action-dimension k; it is conditional on C2 open extension data, a uniform fixed canonical chart for the parameter-dependent Hamiltonian on the zero-residual-force branch, the frequency bound and the trapping of the solution; it asserts no exact invariance, no statement across a separatrix or a chart boundary, and no empirical content.
Statement
Adopt the force model with potential presentation and mechanical Lagrangian of The action functional of a force model with a potential presentation: the mechanical Lagrangian, its chart instance and its dimensions, with the momentum charts and canonical coordinates of The canonical one-form and the two-form of a potential presentation: on the Cartesian momentum phase chart and the induced forms on each generalized-coordinate chart, The two-form of a potential presentation is closed and nondegenerate, and each generalized-coordinate momentum chart carries the same symplectic structure: and and Canonical coordinates and the canonical form of the two-form for a potential presentation: the coordinate expression with the chart's half-dimension, and the model's own momentum charts, the Hamiltonian fields of The Hamiltonian field of a phase function for a potential presentation: the unique field with , and for the branch Hamiltonian and the branch Hamiltonian of The Hamiltonian of a hyperregular potential presentation: the Legendre transform of the mechanical Lagrangian, its domain and its dimensions. Fix one momentum chart and let be a fixed, time-independent one-degree-of-freedom canonical chart of the presentation on an open set of that phase domain, with radian angles and there, obtained from the period-one chart of Action-angle coordinates of a completely integrable presentation: period-one angles, action coordinates, and linear motion on the tori by , as in Period-one to radian action-angle rescaling: and preserve , suppressing the radian superscripts; has the action dimension of clause 2 of that theorem. Use the dimensions of Dimensions and SI unit conventions of the non-relativistic classical mechanics framework: , , , , and . Thus is the prescribed slow parameter rate, is the dimensionless parameter excursion, and is a duration. Let have these dimensions. Let be open intervals, and let and be intervals with nonempty interiors (Intervals of : the nine order-convex forms, nondegeneracy, and length), let and be compact intervals, let , and let
be of class on these open domains, with -periodic in its second variable on ( Euclidean maps and diffeomorphisms). Suppose:
- (slow datum) for every parameter value and every in the chart, the branch Hamiltonian of the model restricted to the chart is
- (nonvanishing frequency) for all ;
- (parameter path and solution) , and on is the chart expression of a motion of the model (on the potential branch, under the identification of clause 4 of Action-angle coordinates of a completely integrable presentation: period-one angles, action coordinates, and linear motion on the tori) satisfying and for every .
Then for every ,
where is the drift generator and the angle average of (A one-frequency parameter-dependent action-angle branch, its transformed Hamiltonian and its drift generator). All partial derivatives are those of the ambient open extensions. The generator has dimension ; each term inside the second supremum has that same dimension, so both terms multiplied by have action dimension. At the included time endpoints, derivatives are relative to the nondegenerate interval .
The statement is conditional on the adopted force branch, the declared presentation, the existence of the uniform action-angle chart, the frequency bound and the trapping hypothesis; it asserts no exact invariance of the action, no statement for parameter paths that leave the chart, cross a separatrix or make the frequency vanish, and no empirical content. In particular the order- bound is a bound on the stated horizon and is not an asymptotic equivalence.
Facts & Assumptions
Given: The presentation, the canonical chart with , the reals , the open extension intervals , their subintervals and compact sets , the point , the functions with -periodic in , the parameter path and the solution with the stated trapping.
Chart data and dimension (Action-angle coordinates of a completely integrable presentation: period-one angles, action coordinates, and linear motion on the tori clauses 1, 2 and 4, Canonical coordinates and the canonical form of the two-form for a potential presentation: the coordinate expression with the chart's half-dimension, and the model's own momentum charts clause (a), Dimensions and SI unit conventions of the non-relativistic classical mechanics framework): by Period-one to radian action-angle rescaling: and preserve , on the presentation's two-form is with radian dimensionless angles and action coordinates of dimension ; in these coordinates the Hamiltonian field of a function has components in the ordered coordinates , so the model's motions in the chart satisfy , .
The datum of the branch (A one-frequency parameter-dependent action-angle branch, its transformed Hamiltonian and its drift generator): with , the branch vector field is , and a branch solution on an interval is a differentiable curve solving that system.
The mathematical drift bound (Adiabatic action drift bound: order- change of the action on the time scale): for the datum with -periodic in , compact intervals , , , reals with on , and a branch solution on with that stays in , the action obeys the displayed order- estimate with the drift generator .
Model reading of the chart evolution (Cartesian model motions on the potential branch and declared generalized-coordinate Lagrange equations integrate their Hamiltonian fields; the forced Cartesian field is Hamiltonian exactly when the residual force has a velocity-independent potential clause 1, Hamilton's equations of the mechanical presentation are equivalent to the model's equation of motion, with residual forces as momentum sources and the coordinate form on every chart clause 1, The associated first-order system, motions, maximal motions and the Newtonian flow of a force model): when , the Cartesian momentum-phase curves of model motions are exactly the integral curves of the branch Hamiltonian field; in a generalized-coordinate immersion, Hamiltonian curves instead correspond to the substituted Lagrange equations, and any reconstructed ambient motion satisfies those equations; in the chart these are the curves of [F1].
Proof
By [F1] and [F4], the chart expression of the model's motion satisfies and for the branch Hamiltonian of hypothesis 1; substituting gives and . With the parameter path from hypothesis 3, the triple therefore solves the branch system of [F2] on .
For the branch solution of step 1.1, the chain-rule calculation in [F3] gives . The sign disappears upon taking absolute values. The compact trapping of hypothesis 3 gives and for every , and hypothesis 2 gives on ; hence all hypotheses of [F3] are met for the branch solution of step 1.1.
Applying [F3] to the branch solution of step 1.1 yields the displayed estimate for every , with the drift generator of the datum; the hypotheses of [F3] were checked in step 2.1.
The estimate of step 3.1 is the conclusion; collecting, the model's action coordinate drifts by at most order on the horizon under the stated hypotheses.
Remarks
-
What the bound does and does not say. The right-hand side is times a constant depending only on the datum through the suprema over the compact set and on the rescaled horizon length ; it grows linearly in and is uniform in . It is not an exact conservation statement: the exact drift of the action is generally nonzero, and the theorem only bounds it.
-
Hypotheses are physical model assumptions. The existence of the uniform fixed canonical chart for the parameter-dependent Hamiltonian with nonvanishing frequency and the trapping of the solution are hypotheses about the model family, not consequences of complete integrability of a single Hamiltonian: a family can pass through a separatrix or a critical frequency, where the estimate does not apply and the action need not be approximately constant. The companion mathematical page records the same qualification for the abstract bound.
Depends on
Period-one to radian action-angle rescaling: and preserve
Action-angle coordinates of a completely integrable presentation: period-one angles, action coordinates, and linear motion on the tori
Completely integrable data of a declared presentation: smooth phase functions with , pairwise in involution and independent on the regular locus
The canonical one-form and the two-form of a potential presentation: on the Cartesian momentum phase chart and the induced forms on each generalized-coordinate chart
The two-form of a potential presentation is closed and nondegenerate, and each generalized-coordinate momentum chart carries the same symplectic structure: and
Canonical coordinates and the canonical form of the two-form for a potential presentation: the coordinate expression with the chart's half-dimension, and the model's own momentum charts
The Hamiltonian field of a phase function for a potential presentation: the unique field with , and for the branch Hamiltonian
Cartesian model motions on the potential branch and declared generalized-coordinate Lagrange equations integrate their Hamiltonian fields; the forced Cartesian field is Hamiltonian exactly when the residual force has a velocity-independent potential
The Hamiltonian of a hyperregular potential presentation: the Legendre transform of the mechanical Lagrangian, its domain and its dimensions
Every potential presentation is hyperregular in its charts, with inverse branch (or ) and the explicit kinetic-plus-potential Hamiltonian
The momentum of a potential presentation: the fibre derivative of the mechanical Lagrangian, the Cartesian momentum Mv and generalized momenta
The action functional of a force model with a potential presentation: the mechanical Lagrangian, its chart instance and its dimensions
Generalized-coordinate maps of the model, the substituted Lagrangian, the kinetic metric and generalized forces
Potential presentations of a force model, potential and mechanical energy, closed versus exact force fields, local potentials and equipotential level sets
Adopted force model: force maps, the equation of motion, additive composition of force contributions and frame covariance
Configuration domain of labeled particles: open admissible sets, regular holonomic constraints and the mass operator
Dimensions and SI unit conventions of the non-relativistic classical mechanics framework
The associated first-order system, motions, maximal motions and the Newtonian flow of a force model
Adiabatic action drift bound: order- change of the action on the time scale
A one-frequency parameter-dependent action-angle branch, its transformed Hamiltonian and its drift generator
The Hamiltonian field of a function on a phase domain is , and the Poisson bracket is
Hamiltonian vector field and Hamiltonian function
Euclidean maps and diffeomorphisms
Directional derivatives and partial derivatives of a map
The Jacobian matrix of partial derivatives and the gradient in the scalar-valued case
The metric topology: a set is open when every one of its points has a ball around it inside the set; closed means open complement
Intervals of : the nine order-convex forms, nondegeneracy, and length
Hamilton's equations of the mechanical presentation are equivalent to the model's equation of motion, with residual forces as momentum sources and the coordinate form on every chart
Dependency tree · 2 levels
Sources
- D. Tong, Classical Dynamics (Cambridge lecture notes, January 2015 printing), Section 4.6, Eqs. (4.148)-(4.158), printed pages 113-115 (PDF pages 119-121): the slow-parameter action calculation and the author's explicit remark that stricter proofs are deferred to the literature
- K. K. Likharev, Essential Graduate Physics, Part CM: Classical Mechanics (title page last edited September 1, 2026), Section 10.2, Eqs. (10.39)-(10.42), chapter pages 5-8 (PDF pages 241-244): the averaged energy-change identity and the adiabatic invariance of the action variable, with stricter proofs of the final statement referred to the literature in the source's footnote
- I. Stewart, Advanced Classical Mechanics (MIT 8.09/8.309 Fall 2014 course text), Chapter 5, Sections 5.2-5.3, Eqs. (5.23)-(5.28), printed pages 96-98 (PDF pages 99-101): secular versus periodic first-order effects after averaging over one period, with no general convergence or remainder theorem