This work is concerned with Hamilton–Jacobi equations of evolution type
posed in domains and supplemented with boundary conditions. Hamiltonians
are coercive but are neither convex nor quasiconvex. We analyze boundary
conditions when understood in the sense of viscosity solutions. This analysis is
based on the study of boundary conditions of evolution type. More precisely,
we give a new formula for the relaxed boundary conditions derived by J.
Guerand (J. Differential Equations263:5 (2017), 2812–2850). This new
point of view unveils a connection between the relaxation operator and the
classical Godunov flux from the theory of conservation laws. We apply our
methods to two classical boundary value problems. It is shown that the relaxed
Neumann boundary condition is expressed in terms of Godunov’s flux while
the relaxed Dirichlet boundary condition reduces to an obstacle problem
at the boundary associated with the lower nonincreasing envelope of the
Hamiltonian.
Keywords
Hamilton–Jacobi equations, initial and boundary value
problems, viscosity solutions