マクスウェルの応力テンソル
∇ ⋅ T = ( ∇ ⋅ D ) E − D × ( ∇ × E ) + ( ∇ ⋅ B ) H − B × ( ∇ × H ) = ρ E + D × ∂ B ∂ t − B × ∂ D ∂ t − B × j = ∂ ( D × B ) ∂ t + ρ E + j × B {\displaystyle {\begin{aligned}\nabla \cdot \mathrm {T} &=(\nabla \cdot {\boldsymbol {D}}){\boldsymbol {E}}-{\boldsymbol {D}}\times (\nabla \times {\boldsymbol {E}})+(\nabla \cdot {\boldsymbol {B}}){\boldsymbol {H}}-{\boldsymbol {B}}\times (\nabla \times {\boldsymbol {H}})\\&=\rho {\boldsymbol {E}}+{\boldsymbol {D}}\times {\frac {\partial {\boldsymbol {B}}}{\partial t}}-{\boldsymbol {B}}\times {\frac {\partial {\boldsymbol {D}}}{\partial t}}-{\boldsymbol {B}}\times {\boldsymbol {j}}\\&={\frac {\partial ({\boldsymbol {D}}\times {\boldsymbol {B}})}{\partial t}}+\rho {\boldsymbol {E}}+{\boldsymbol {j}}\times {\boldsymbol {B}}\\\end{aligned}}}