Theory and Applications of Information-Based Complexity

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Proposal #0097348Traub, Joseph F.Columbia UniversityThere is huge interest in solving high dimensional problems. Many applications involve functions of hundreds, thousands or even an infinite number of variables. Examples occur in physics, chemistry,mathematical finance, and economics. It is the rare high dimensional problem that can be solved analytically. Generally one must settle for an approximate numerical solution to within an error e. The computational complexity is the minimal computational resource need to solve a problem to within e. Time is the resource consideredand is measured by the number of information operations, arithmetic operations and comparisons. An example of an information operation is the computation of a function value.If a worst case deterministic assurance of an e-approximation is desired, then often the computational complexity depends exponentially on the number of variables d; the problem suffers the "curse ofdimensionality". Examples include integration, approximation, globaloptimization, integral and partial differential equations over typical isotropic classical spaces of r-times continuously differentiablefunctions. If the computational complexity is exponential in either 1/e or d the problem is said to be intractable. If the complexity is polynomial in 1/e and d, it is tractable. If, in addition, the minimal number of information operations, arithmetic operations and comparisons is independent of d the problem is strongly tractable. Intractability may sometimes be broken by settling for a stochastic assurance of error; examples are randomization (for instance, Monte Carlo) or the average case. A second way in which intractability mightbe broken is additional domain knowledge about the problem. An example of the domain knowledge is that the integrands in certain mathematical finance problems are non-isotropic. Additional domain knowledge can sometimes be used to make the problem strongly tractable even in the worst case deterministic setting!Continuation of research on achieving tractability and strong tractability is proposed. In particular, one proposed area of research is under what conditions is a double-win achievable for high dimensional integration: * convergence faster than Monte Carlo, * with a worst case deterministic assurance.The theoretical results will be used to improve the FinDer software system. More generally, research is proposed on the following topics: * Theory and Computer Experiments for Mathematical Finance, * Tractability of Quasi-Monte Carlo and Monte Carlo Algorithms, * Variable Smoothness, * Generalized Tractability.