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Let$X$be a complex manifold with finitely many ends such that each end is either$q$-concave or ($n−q$)-convex. If $$q< \tfrac{1}{2}n$$ , then we prove that$H$^{p$n−q$}$(X)$is Hausdorff for all$p$. This is not true in general if $$q \geqslant \tfrac{1}{2}n$$ (Rossi’s example with$n$=2 and$q$=1). If all ends are$q$-concave, then this is the classical Andreotti-Vesentini separation theorem (and holds also for $$q \geqslant \tfrac{1}{2}n$$ ). Moreover the result was already known in the case when the$q$-concave ends can be ‘filled in’ (again also for $$q \geqslant \tfrac{1}{2}n$$ ). To prove the result we first have to study Serre duality for the case of more general families of supports (instead of the family of all closed sets and the family of all compact sets) which is the main part of the paper. At the end we give an application to the extensibility of CR-forms of bidegree ($p, q$) from ($n−q$)-convex boundaries, $$q< \tfrac{1}{2}n$$ .

We prove that for the cases $X=\mathcal{C}(K)$ ($K$infinite) and$X$=$L$_{1}(μ) (μ σ-finite and atomless) it holds that every slice of the unit ball of the$N$-fold symmetric tensor product of$X$has diameter two. In fact, we prove more general results for weak neighborhoods relative to the unit ball. As a consequence, we deduce that the spaces of$N$-homogeneous polynomials on those classical Banach spaces have no points of Fréchet differentiability.

We give a characterization of Possonian domains in$R$^{$n$}, i.e., those domains for which every bounded harmonic function is the harmonic extension of some function in$L$^{∞}of harmonic measure. We deduce several properties of such domains, including some results of Mountford and Port. In two dimensions we give an additional characterization in terms of the logarithmic capacity of the boundary. We also give a necessary and sufficient condition for the harmonic measures on two disjoint planar domains to be mutually singular.

A new fundamental and secure group key management approach with a group controller GC using the theory of polynomial functions over a vector space over finite field is developed, where each member in the group corresponds to a vector in the vector space and the GC computes a central vector, whose inner product with every member's ID vector are identical. The central vector is published and each member can compute a common group key via inner product. The security relies on the fact that any illegitimate user cannot calculate this value without the legitimate vector, therefore cannot derive the group key. This approach is secure and its backward and forward secrecy can be guaranteed. The performance of our approach is analyzed to demonstrate its advantages in comparison with others, which include: 1) it requires both small memory and little computations for each group member; 2) it can handle massive membership change efficiently with only two re-keying messages, i.e., the central vector and a random number; 3) it is very efficient and very scalable for large size groups. Our experiments confirm these advantages and the implementation of our prototype presents very satisfactory performance for large size groups.