Barth type vanishing theorems

Let X be a smooth, projective, d-dimensional subvariety of ⁿ (). Barth's theorem says that H ^q (X, ^p _X )=0 when pq and q+p2d–n (if p=0 we must have q>0). It is very interesting to look for analogous vanishing theorems for H ^q (X, ^p _X (m)), m (see [S-S], [F], [S]). In this paper we prove some vanishing theorems for H ^q (X, ^p _X (1)), for H ^q (X, ^p _X (m)) when m–1, and, if dim(X)=n–2, for H ^q (X, ² _X (m)) and H ^q (X, S ^{k 1} _X (m)). We use standard techniques and some of our previous results.     

Schur-Ostrowski type theorems revisited

In this paper we extend Schur-Ostrowski theorem on Schur-convex functions from majorized vectors to separable ones. For this, we introduce a generalized Schur-Ostrowski?s condition. We apply the obtained result for cone orderings and group-induced cone orderings. Finally, we give some interpretations for absolutely weak majorization and for group majorization on the space of complex matrices.     

Paley-Wiener type theorems by transmutations

The classical Paley-Wiener theorem for functions in L _dx ² relates the growth of the Fourier transform over the complex plane to the support of the function. In this work we obtain Paley-Wiener type theorems where the Fourier transform is replaced by transforms associated with self-adjoint operators on L _dμ ² , with simple spectrum, where dμ is a Lebesgue-Stieltjes measure. This is achieved via the use of support preserving transmutations. Communicated by Paul L. Butzer     

Minimax type theorems forn-valued functions

Summary We consider in R ⁿ the ordering induced by a cone and give suitable definitions of Sup, Inf,convexity and lower semicontinuity relative to n-valued functions: in this framework we can prove minimax theorems for such a class of functions.This work was partially supported by Istituto per la Matematica Applicata del C.N.R. (Genova).     

Gabriel-Popescu type theorems and applications

In this paper we obtain a general version of Gabriel-Popescu theorem representing any Grothendieck category as a quotient category of the category of modules over a ring (not necessarily with unit) with enough idempotents to right using a family of generators (U_i)_i∈I of where U_i are not supposed to be small. Applications to locally finite categories are obtained. In particular, for a coalgebra C (over a field) we prove that C is right semiperfect if and only if the category has the AB4∗ condition.     

New Pólya-Schoenberg type theorems

In this paper the theory of Hadamard product multipliers is extended from the unit disk in the complex plane to arbitrary so-called disk-like domains, i.e. such domains which are the union of disks or half-planes, all containing the origin. In such a domain, say Ω, we define (the class of) generalized prestarlike functions of order α?1 and ask for Hadamard multipliers g analytic at z=0 for which implies . We prove that such a multiplier necessarily has to be analytic in

     

Bernstein type theorems for higher codimension

We show a Bernstein theorem for minimal graphs of arbitrary dimension and codimension under a bound on the slope that improves previous results and is independent of the dimension and codimension. The proof depends on the regularity theory for the harmonic Gauss map and the geometry of Grassmann manifolds. Received: September 25, 1998 / Accepted: October 23, 1998     

Uniqueness theorems for Korenblum type spaces

For a scale of spaces X of functions analytic in the unit disc, including the Korenblum space, and for some natural families ɛ of uniqueness subsets for X, we describe minorants for (X, ɛ), that is, non-decreasing functions M: (0, 1) → (0, ∞) such that f ∈ X, E ∈ ɛ, and log |f(z)| ≤ −M(|z|) on E imply f = 0. We give an application of this result to approximation by simple fractions with restrictions on the coefficients. The first author was partially supported by the ANR project DYNOP. The second author was partially supported by the Research Council of Norway, grant 160192/V30.     

More on monochromatic-rainbow Ramsey type theorems

An edge colored graph is called a rainbow if no two of its edges have the same color. Let ? and $\mathcal{G}$ be two families of graphs. Denote by $RM({\mathcal{H}},\mathcal{G})$ the smallest integer R, if it exists, having the property that every coloring of the edges of K _R by an arbitrary number of colors implies that either there is a monochromatic subgraph of K _R that is isomorphic to a graph in ? or there is a rainbow subgraph of K _R that is isomorphic to a graph in $\mathcal{G}$ . ${\mathcal{T}}_{n}$ is the set of all trees on n vertices. ${\mathcal{T}}_{n}(k)$ denotes all trees on n vertices with diam(T _n (k))≤k. In this paper, we investigate $RM({\mathcal{T}}_{n},4K_{2})$ , $RM({\mathcal{T}}_{n},K_{1,4})$ and $RM({\mathcal{T}}_{n}(4),K_{3})$ .     

Simple proofs of Olevskii type theorems

Olevskii's theorem and one of its generalizations are proved by methods of functional analysis.Translated fromMatematicheskie Zametki, Vol. 59, No. 3, pp. 343–350, March, 1996.     

KKM type theorems with boundary conditions

We consider generalizations of Gale’s colored KKM lemma and Shapley’s KKMS theorem. It is shown that spaces and covers can be much more general and the boundary KKM rules can be substituted by more weaker boundary assumptions.     

Functorial semantics and HSP type theorems

We show that if ] is the category of models for a theory in the sense of Linton over an arbitrary base category, then a full subcategory of ] is closed under Homomorphic images that split in the underlying category, under -Subobjects for a class of monomorphisms and under Products if and only if it is an intersection of a nest of subcategories, each determined from the preceding by a class of Horns, in which the crucial arrow lies in the class of epimorphisms orthogonal to .Dedicated to the memory of Evelyn Nelson, Alan Day and Alan MeklerPresented by F. E. J. Linton.This research has been supported by grants from the NSERC of Canada and the FCAR du Québec.     

Comparison theorems for hyperbolic type metrics

The connection between several hyperbolic type metrics is studied in subdomains of the Euclidean space. In particular, a new metric is introduced and compared to the distance ratio metric.