In a note at the end of his paper Recherches sur les fractions continues, Stieltjes gave a necessary and sufficient condition when a continued fraction is represented by a meromorphic function. This result is related to the study of compact Jacobi matrices. We indicate how this notion was developped and used since Stieltjes, with special attention to the results by M.G. Krein. We also pay atten...

This note is devoted to the study of the dependence on p of the constant in the reverse Brunn-Minkowski inequality for p-convex balls (i.e. p-convex symmetric bodies). We will show that this constant is estimated as c ≤ C(p) ≤ C , for absolute constants c > 1 and C > 1. Let K ⊂ IR n and 0 < p ≤ 1. K is called a p-convex set if for any λ, μ ∈ (0, 1) such that λ + μ = 1 and for any points x, y ∈ ...

We present the current state of the art concerning the global and local Markov inequalities in the complex plane. This paper is based on a talk given during the Workshop on Multivariate Approximation in honor of Prof. Len Bos 60th birthday, and rests on articles [4], [5] and [6]. Our research is inspired by papers by Bos and Milman where global and local Markov inequalities are compared in the ...

We investigate the strength of set existence axioms needed for separable Banach space theory. We show that a very strong axiom, Π1 comprehension, is needed to prove such basic facts as the existence of the weak-∗ closure of any norm-closed subspace of `1 = c0. This is in contrast to earlier work [6, 4, 7, 23, 22] in which theorems of separable Banach space theory were proved in very weak subsys...

We analyze a multi-type age dependent model for cell populations subject to unidirectional motion, in both a stochastic and deterministic framework. Cells are distributed into successive layers; they may divide and move irreversibly from one layer to the next. We adapt results on the large-time convergence of PDE systems and branching processes to our context, where the Perron-Frobenius or Krei...

This paper presents analogs, for certain mixed boundary-value problems, of the spectral and oscillatory properties exhibited by classical Sturm-Liouville systems. ‘l’he usual analysis of the Sturm-Liouville eigenvalue problem is based on special ad hoc methods. In contrast, Gantmacher and Krein [3; see also references therein] showed that these fundamental spectral properties are direct consequ...

— We give a proof, based on the Poincaré inequality, of the symmetric property (τ) for the Gaussian measure. If f :Rd → R is continuous, bounded from below and even, we define Hf(x) = infy f(x+y)+ 1 2 |y|2 and we have ∫ e−f dγd ∫ e dγd 1. This property is equivalent to a certain functional form of the BlaschkeSantaló inequality, as explained in a paper by Artstein, Klartag and Milman. RÉSUMÉ. —...

λ0 = λ0(1, P, Ω) := sup{λ ∈ R : ∃u > 0 s.t. (P − λ)u ≥ 0 in Ω}, where 1 is the constant function on Ω, taking at any point x ∈ Ω the value 1. Using the Krein-Rutman theorem, the author proved in [13, 14] generalized maximum principles and anti-maximum principles (in brief, GMPs and AMPs, respectively) for the problem (P − λ)uλ = f 0 in Ω. (1.1) In particular, these GMPs and AMPs (without weight...

A bounded operator T on a separable, complex Hilbert space is said to be odd symmetric if IT I = T where I is a real unitary satisfying I = −1 and T t denotes the transpose of T . It is proved that such an operator can always be factorized as T = IAIA with some operator A. This generalizes a result of Hua and Siegel for matrices. As application it is proved that the set of odd symmetric Fredhol...