The static isotropic elasticity system balances the stress generated by a displacement field. On a domain in 
, the strain tensor and
stress tensor are
 |
and the equilibrium equation is 
. The real
Lamé coefficients 
may vary with position. The conditions 
and 
give positive
strain energy. The Dirichlet-to-Neumann
operator sends boundary displacement to traction
,
where 
is the outward unit normal.
