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Augmented energy and passive absorption
Conditional local energy identities and fixed-volume passive-energy balances for the finite Lorentz oscillator closure and the Drude current closure, in one homogeneous material rest frame under the stated smoothness and finite-energy Maxwell hypotheses. The undriven nonincrease result is for the closure-defined PEC branch. No existence theorem, microscopic explanation, empirical material claim, or energy law outside these constitutive branches is asserted.
Statement
Let be a nonempty open interval and let be a nonempty bounded Lipschitz polyhedron in one material rest frame. Use real SI fields: , a free current density , polarization , and, when present, carrier current . Their units are V m, A m, C m, T, A m, C m and A m, respectively. Let and be constant scalar coefficients in F m and H m. Each is in J m and the flux is in W m.
Assume Countable Choice, the smooth macroscopic Maxwell material model, and its curl equations
hold pointwise. The smooth macroscopic material model includes continuous free sources and the total polarization/magnetization identifications specified by the Lorentz or Drude closure. Assume are jointly pointwise and satisfy ; and each material-current term belong to . Here is the real vector fields whose distributional curl is represented by an vector field, with the graph norm. Take Lorentz fields jointly and in , or Drude fields jointly with , so that the stored energies and current terms are finite. Take either one of the following constitutive branches:
- Finite Lorentz branch. For some finite , , , and where is jointly , in F m s, in s, and in s.
- Drude branch. , , , and , where are jointly , in F m s, and in s.
For the Lorentz branch define
For the Drude branch define
The Lorentz density is positive definite in . The Drude density is positive definite in ; a constant polarization offset is not part of this energy.
Then the respective local identities hold pointwise:
If, in addition, the fields satisfy the exact closure-defined PEC branch of the finite-energy boundary model and , then the total stored energy or is nonnegative and nonincreasing. More generally the corresponding fixed-volume balance includes the work and the displayed nonnegative material-loss terms; no claim of conservation without these terms is made.
Statement references
Finite-energy PEC and impedance boundary formulation
Finite Lorentz oscillator closure
Drude current closure and collisionless limit
The macroscopic Maxwell equations in terms of D, H and the free sources
The Axiom of Countable Choice ()
Energy balance and zero-data forward uniqueness for admissible weak Maxwell fields
Facts & Assumptions
Given: Countable Choice, the bounded-domain, time-regularity, SI, and closure-defined PEC conventions of the finite-energy boundary model; either the finite Lorentz branch or the Drude branch and its stated coefficients; the pointwise Maxwell curl equations and local regularity in the Statement.
The Lorentz closure is the real, homogeneous, spatially local constitutive model , , , with , , and oscillator initial state . Its macroscopic identification is and (Finite Lorentz oscillator closure).
The Drude closure is , , , , with , and the initial polarization state specified separately from . Its macroscopic identification is and (Drude current closure and collisionless limit).
Countable Choice is assumed, as required by the weak Maxwell energy supplier's real convention (The Axiom of Countable Choice ()).
In the finite-energy boundary model, consists of vector fields whose distributional curl is represented by an field; the PEC condition is the graph-norm closure definition of , not an unproved identification with a trace kernel (Finite-energy PEC and impedance boundary formulation).
For real vector fields, (The divergence and curl of a cross product).
The Euclidean product is a symmetric positive-definite real bilinear form, so and its componentwise pairing obeys the product rule (The Euclidean inner product on ).
For differentiable real scalar functions, sums, products and scalar multiples obey their usual derivative rules; these apply componentwise to the field squares and oscillator energies (Sums, scalar multiples, products and quotients: , , , and when ).
For smooth macroscopic material fields, , , , and (The macroscopic Maxwell equations in terms of D, H and the free sources, clause (b)).
For the finite-energy Maxwell model with time-independent bounded symmetric uniformly positive coefficients, fields, and the two evolution identities, the closure-defined PEC branch satisfies , where (Energy balance and zero-data forward uniqueness for admissible weak Maxwell fields, Statement).
Proof
In either branch put for Lorentz, and for Drude. By [L1], or and ; also . Thus , and [F3]–[F4] give . By [F2], this is in the Lorentz branch, and in the Drude branch.
In the Lorentz branch, dot the th oscillator equation with . By [F3]–[F4], the product rule gives . The division is valid since ; the term is the derivative of the potential-energy term and the damping term is nonnegative.
In the Drude branch, dot with . By [F3]–[F4] and , and . The last term is nonnegative because .
Substituting step 1.2 into the Lorentz balance of step 1.1 cancels every term and yields the displayed identity for . Substituting step 1.3 into the Drude balance of step 1.1 cancels and yields the displayed identity for . These are pointwise identities under the stated local regularity; they do not require a boundary condition.
For the Lorentz fixed-volume conclusion, the fields in step 1.1 satisfy the weak model of [L2] with coefficient maps , and current . These are static symmetric uniformly positive maps, and by the hypotheses. Apply [L2] to obtain the field-energy change . Integrating step 1.2 over adds ; the polarization work cancels the same term in . Hence . The same argument in the Drude branch uses , applies [L2] with the same constant positive coefficients, and adds the integral of step 1.3, giving . The PEC boundary contribution is zero by the exact PEC branch in [L2].
In either branch, (or ) are strictly positive, so [F3] makes the displayed densities nonnegative. The Lorentz density vanishes only when all vanish; the Drude density vanishes exactly when vanish, without constraining a constant polarization offset. With , every term on the right sides in step 2.2 is nonpositive because each . Thus or for in , and both are nonnegative energies. This is a conditional model deduction, not an empirical claim.
Depends on
Finite-energy PEC and impedance boundary formulation
The Axiom of Countable Choice ()
The divergence and curl of a cross product
The Euclidean inner product on
Finite Lorentz oscillator closure
Drude current closure and collisionless limit
The macroscopic Maxwell equations in terms of D, H and the free sources
Energy balance and zero-data forward uniqueness for admissible weak Maxwell fields
Sums, scalar multiples, products and quotients: , , , and when
Dependency tree · 2 levels
Sources
- David Tong, Electromagnetism, University of Cambridge Part II Mathematical Tripos lecture notes (236-page complete text)
- Richard Fitzpatrick, Classical Electromagnetism: An intermediate level course, complete University of Texas at Austin lecture notes
- Niklas Beisert, Elektrodynamik, ETH Zurich 2024 FS complete lecture script