arXiv subjects

Charles L. Epstein

Publications and source records attributed to Charles L. Epstein.

40 records · Page 3Linked to original sources

arXiv2007

Cobordism, Relative Indices and Stein Fillings

In this paper we build on the framework developed in "Subelliptic Boundary Value Problems for the Spin_C Dirac Operator, I, II, III" to obtain a more complete understanding of the gluing properties for indices of boundary value problems for the SpinC-Dirac operator with sub-elliptic boundary conditions. We extend our analytic results for sub-elliptic boundary value problems for the SpinC-Dirac operator, and gluing results for the indices of these boundary problems to SpinC-manifolds with several pseudoconvex (pseudoconcave) boundary components. These results are applied to study Stein fillability for compact, 3-dimensional, contact manifolds.

math.AP↗

arXiv2007

Subelliptic Spin_c Dirac operators, III The Atiyah-Weinstein conjecture

In this paper we show that there is a well defined modified dbar-Neumann problem for a spin_c manifold with a strictly pseudoconvex boundary (in the contact geometry sense). We show that the index of the associated boundary value problem can be computed as the relative index between the Calderon projector on the boundary and the projector defining the boundary condition. To make sense of this statement we need to develop a considerable extension of the classical notion of a Fredholm pair of subspaces of a Hilbert space. We call this the theory of "tame Fredholm pairs;" it is presented in the appendix to the paper. Using these tools, we give a proof of a conjecture of Atiyah and Weinstein for the index of a Fourier integral operator defined by a contact transformation between the boundaries of two strictly pseudoconvex manifolds. In fact, we prove a much more general result expressing the relative index between two generalized Szego projectors as the index of a Dirac operator on a compact "glued" space with correction terms coming from boundary value problems. The Atiyah-Weinstein conjecture is a simple special case of this general formula. Special cases of this result were earlier proved by Epstein and Melrose, and Leichtnam, Nest and Tsygan. Using our general formula for relative indices, we also obtain a formula for the relative index between two Szego projectors defined by embeddable CR-structures on a contact three manifold. Using this formula, we reduce a conjecture about the boundedness of these relative indices to a conjecture of A. Stipsicz on the boundedness of the Euler characteristics and signatures of Stein manifolds with a given contact boundary. This latter conjecture has been proved in many cases of interest.

math.AP↗

arXiv2006

Tempering the polylogarithm

We show that the function Li_s(e^x) extends to an entire function of the complex variable s, taking values in tempered distributions in x on the whole real line. That the classical polylogarithm extends similarly, as an entire function taking values in distributions on compactly-supported functions on the positive real axis, is a corollary. We then identify the singularities of Li_s(e^x) in terms of distribution powers of x; this leads to a simple proof of the smoothness of the `modified' polylogarithm of Bloch, Ramakrishnan, Wigner, Wojtkowiak, Zagier, and others.

math.CA↗

arXiv2006

Anderson Localization, Non-linearity and Stable Genetic Diversity

In many models of genotypic evolution, the vector of genotype populations satisfies a system of linear ordinary differential equations. This system of equations models a competition between differential replication rates (fitness) and mutation. Mutation operates as a generalized diffusion process on genotype space. In the large time asymptotics, the replication term tends to produce a single dominant quasispecies, unless the mutation rate is too high, in which case the populations of different genotypes becomes de-localized. We introduce a more macroscopic picture of genotypic evolution wherein a random replication term in the linear model displays features analogous to Anderson localization. When coupled with non-linearities that limit the population of any given genotype, we obtain a model whose large time asymptotics display stable genotypic diversity

q-bio.PE↗