Year 2000 problem | Waring's problem | The Final Problem | The Problem with Popplers | Hume and the Problem of Causation | Dirichlet problem | Boolean satisfiability problem | The Dog Problem | Tammes problem | Species problem | problem solving | Problem gambling | Packing problem | packing problem | chess problem | Znám's problem | Year 10,000 problem | Yamabe problem | Weber problem | Undecidable problem | Travelling salesman problem | travelling salesman problem | The Problem of Thor Bridge | The Problem of the Media: U.S. Communication Politics in the 21st Century | The Problem of Social Cost | Tarski's circle squaring problem | Steiner tree problem | Shortest path problem | RSA problem | Quadratic eigenvalue problem |
In any physical theory, it is important to understand when solutions to the fundamental field equation exist, and answering this question has been the central theme of York's scientific work, culminating in the achievement, with Yvonne Choquet-Bruhat, of formulating the Einstein field equation as a well-posed system in the sense of the theory of partial differential equations.
He also substantially contributed to the development of the theory of capacities, nonlinear potential theory, the asymptotic and qualitative theory of arbitrary order elliptic equations, the theory of ill-posed problems, the theory of boundary value problems in domains with piecewise smooth boundary.