Abstract.We prove a uniqueness and existence theorem for the entropy weak solution of nonlinear hyperbolic conservation laws of the form jL(ru) + |_(r/(tt))=0, dt ox with initial data and boundary condition. The scalar function u = u(x,t), x > 0, t > 0, is the unknown, the function / = f(u) is assumed to be strictly convex with inf /(•) = 0 and the weight function r = r(x), x > 0, to be positive (for example, r(x) = xa, with an arbitrary real a).We give an explicit formula, which generalizes a result of P. D. Lax. In particular, a free boundary problem for the flux r(-)f(u(-, ■)) at the boundary is solved by introducing a variational inequality.The uniqueness result is obtained by extending a semigroup property due to B. L. Keyfitz.
Introduction.We consider weighted scalar nonlinear hyperbolic conservation laws of the formwhere the scalar function u = u(x,t), x > 0, t > 0, is the unknown. The flux function / = f(u) is assumed to be strictly convex with inf /(•) = 0 and the weight function r = r(x), x > 0, to be positive. This paper is concerned with the mixed problem associated with the equation (0.1): we are looking for a solution u = u(x,t) of (0.1), satisfying an initial data and a boundary condition. But, it is well known that conservation laws of the type (0.1) do not possess classical solutions, even when the initial data is smooth: discontinuities appear in finite time. Hence, we consider only weak solutions of (0.1), that is solutions in the sense of distributions. And, for the sake of uniqueness, we have to add an entropy condition that selects the physical (or entropy) solution among all the solutions in the sense of distributions.For a convex flux function /(•), the entropy condition is written as We are interested (in particular) in the case where the function r = r(x) tends to zero at the point z = 0 or at the point z = +oo. For example, we can take r(x) = xa (a E R). In such a case, the equation (0.1) possesses an algebraic