The Neumann Problem for the Tangential Cauchy-Riemann Complex and the CR Embedding Problem

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SupermanSProposal DMS-0406060PI: John M. Lee, University of WashingtonThe Neumann Problem for the Tangential Cauchy-Riemann Complex and the CREmbedding ProblemABSTRACTTechnical description of the project:The proposed research will study existence and regularity theorems for thenatural Neumann boundary problem for the tangential Cauchy-Riemann equationson smoothly bounded domains in CR manifolds. All known existence resultsfor this problem work only on domains with very special defining functions,namely those that depend only on the real and imaginary parts of a singleCR-holomorphic function. The key idea of this research is to use the factthat such a defining function provides a codimension-2 foliation (near theboundary but away from characteristic points) by compact CR-submanifolds.By using known estimates for the Kohn Laplacian on the compact leaves, onecan reduce the Neumann problem to a (generally non-coercive) ellipticboundary problem in a plane domain. These results are expected to haveapplications to such problems as the local CR embedding problem, localdeformations of CR structures, characterizing domains on which thetangential Cauchy-Riemann complex is solvable, regularity of maps between CRmanifolds, and the existence of local frames for CR vector bundles.Non-technical description:The geometry of complex manifolds (geometric objects in which complexnumbers instead of real numbers can be used as coordinates) has recentlybegun to play a surprisingly important role in both mathematics and physics.For example, in string theory, physicists postulate that the fundamentalparticles of matter are actually "quantum strings" that vibrate insidesub-microscopic complex manifolds called Calabi-Yau manifolds. Theprincipal analytic tool for studying complex manifolds is the Cauchy-Riemannequations, a system of partial differential equations that characterizes,among other things, those functions that have complex derivatives. When onestudies surfaces within complex manifolds (such as the "branes" that arisein string theory), the Cauchy-Riemann equations need to be replaced by amuch more complicated system called the "tangential Cauchy-Riemannequations," which we are just beginning to understand. This proposal willdevelop new techniques for studying some deep analytic questions surroundingthe solvability of the tangential Cauchy-Riemann equations, which areexpected to be of fundamental importance in understanding the geometry andanalysis of surfaces in complex manifolds.