Rendezvous numbers in normed spaces

Rendezvous numbers of metric spaces - a potential theoretic approach

The present work draws on the understanding how notions of general potential theory - as set up, e.g., by Fuglede - explain existence and some basic results on the "magical" rendezvous numbers. We aim at a fairly general description of rendezvous numbers in a metric space by using systematically the potential theoretic approach. In particular, we generalize and explain results on invariant measures, hypermetric spaces and maximal energy measures, when showing how more general proofs can be found to them.

Potential theoretic approach to rendezvous numbers

We analyze relations between various forms of energies (reciprocal capacities), the transfinite diameter, various Chebyshev constants and the so-called rendezvous or average number. The latter is originally defined for compact connected metric spaces (X,d) as the (in this case unique) nonnegative real number r with the property that for arbitrary finite point systems {x1,...,xn} in X, there exists some point x in X with the average of the distances d(x,xj) being exactly r. Existence of such a miraculous number has fascinated many people; its normalized version was even named "the magic number"…

Some polynomial inequalities on real normed spaces

We consider various inequalities for polynomials, with an emphasis on the most fundamental inequalities of approximation theory. In the sequel a key role is played by the generalized Minkowski functional α(K,x), already being used by Minkowski and contemporaries and having occurred in approximation theory in the work of Rivlin and Shapiro in the early sixties. We try to compare real, geometric methods and complex, pluripotential theoretical approaches, where possible, and formulate a number of questions to be decided in the future. An extensive bibliography is given to direct the reader even i…

Inequalities for Multivariate Polynomials

We summarize researches - in great deal jointly with my host Y. Sarantopoulos and his PhD. students V. Anagnostopoulos and A. Pappas - started by a Marie Curie fellowship in 2001 and is still continuing. The project was to study multivariate polynomial inequalities. In the course of work we realized the role of the ``generalized Minkowski functional'', to which we devoted a throughout survey. Resulting from this, infinite dimensional extensions of Chebyshev's extremal problems were tackled successfully. Investigating Bernstein-Markov constants for homogeneous polynomials of real normed spaces …

一致可求长度度量空间中的弱Carleson条件：WCD与alpha数

Weak Carleson conditions in uniformly rectifiable metric spaces: the WCD and alpha numbers

该研究通过弱Carleson条件刻画一致可求长度度量空间，证明UR空间满足弱常数密度条件，引入度量空间版alpha数并证明其弱Carleson条件可刻画度量一致可求长度性，且两结果均为更一般抽象结论的推论。