Weak and entropy physics-informed neural networks for conservation laws

Abstract: We propose Weak and Entropy PINNs (WE-PINNs) for the approximation of entropy solutions to nonlinear hyperbolic conservation laws. Standard physics-informed neural networks enforce governing equations in strong differential form, an approach that becomes structurally inconsistent in the presence of discontinuities due to the divergence of strong-form residuals near shocks. The proposed method replaces pointwise residual minimization with a space--time weak formulation derived from the divergence theorem. Conservation is enforced through boundary flux integrals over dynamically sampled space--time control volumes, yielding a mesh-free control-volume framework that remains well-defined for discontinuous solutions. Entropy admissibility is incorporated in integral form to ensure uniqueness and physical consistency of the weak solution. The resulting loss functional combines space--time flux balance and entropy inequalities, without resorting to dual-norm saddle-point formulations, auxiliary potential networks, or fixed discretization meshes. This makes the proposed method remarkably easy to implement, requiring only a simple standard neural network architecture. We establish a rigorous convergence analysis linking the network's loss function to the $L^1$ error towards the entropy solution, providing the first explicit $L^1$ convergence rate for a mesh-free control-volume PINN formulation via the Bouchut-Perthame framework for scalar conservation laws. Numerical experiments on the Burgers equation, the shallow water equations, and the compressible Euler equations demonstrate accurate shock resolution and robust performance in both smooth and shock-dominated regimes.