作者：BOYLE, M; HANDELMAN, D
摘要：We characterize (by elementary conditions) those k-tuples of complex numbers which are the nonzero portion (including multiplicities) of the spectrum of a nonnegative real matrix. The proof relies on methods and results from symbolic dynamics. More generally, let S be a unital subring of the reals. We conjecture that certain elementary necessary conditions are sufficient for a k-tuple DELTA of complex numbers to be the nonzero portion of the spectrum of a primitive matrix over S. (The general ...
作者：ANGENENT, S
摘要：We describe a theory for parabolic equations for immersed curves on surfaces, which generalizes the curve shortening or flow-by-mean-curvature problem, as well as several models in the theory of phase transitions in two dimensions. A class of equations is described for which the initial value problem is well-posed for rough initial data, for which one can give a description of the way a smooth solution becomes singular, and for which one can define generalized solutions, i.e., solutions which ...
作者：FEFFERMAN, RA; KENIG, CE; PIPHER, J
