Solutions of the heat equation in domains with singularities

We study the asymptotics of solutions to the Dirichlet problem for the heat equation in time-dependent domains with singular points.Translated fromMatematicheskie Zametki, Vol. 64, No. 2, pp. 163–179, August, 1998.This research was supported by the Russian Foundation for Basic Research under grant No. 96-01-00504 and by INTAS under grant No. 93-351.     

On Lipschitz and D.C. surfaces of finite codimension in a Banach space

Properties of Lipschitz and d.c. surfaces of finite codimension in a Banach space and properties of generated σ-ideals are studied. These σ-ideals naturally appear in the differentiation theory and in the abstract approximation theory. Using these properties, we improve an unpublished result of M. Heisler which gives an alternative proof of a result of D. Preiss on singular points of convex functions.     

Computing the Top Betti Numbers of Semialgebraic Sets Defined by Quadratic Inequalities in Polynomial Time

For any ℓ>0, we present an algorithm which takes as input a semi-algebraic set, S, defined by P ₁≤0,…,P _s ≤0, where each P _i ∈R[X ₁,…,X _k ] has degree≤2, and computes the top ℓ Betti numbers of S, b _k−1(S),…,b _k−ℓ (S), in polynomial time. The complexity of the algorithm, stated more precisely, is . For fixed ℓ, the complexity of the algorithm can be expressed as , which is polynomial in the input parameters s and k. To our knowledge this is the first polynomial time algorithm for computing nontrivial topological invariants of semialgebraic sets in R ^k defined by polynomial inequalities, where the number of inequalities is not fixed and the polynomials are allowed to have degree greater than one. For fixed s, we obtain, by letting ℓ=k, an algorithm for computing all the Betti numbers of S whose complexity is . An erratum to this article can be found at     

Heinz‐type inequality and bi‐Lipschitz continuity for quasiconformal mappings satisfying inhomogeneous biharmonic equations

Let be the class of all sense‐preserving homeomorphic self‐mappings of . The aim of this paper is twofold. First, we obtain Heinz‐type inequality for (K,K′)‐quasiconformal mappings satisfying inhomogeneous biharmonic equation Δ(Δω) = g in unit disk with associated boundary value conditions and . Second, we establish biLipschitz continuity for (K,K′)‐quasiconformal mappings satisfying aforementioned inhomogeneous biharmonic equation when and are small enough.     

The additivity of porosity ideals

We show that several -ideals related to porous sets have additivity and cofinality . This answers a question addressed by Miroslav Repický.

     

On the size of the fibers of spectral maps induced by semialgebraic embeddings

Let be the ring of (continuous) semialgebraic functions on a semialgebraic set M and its subring of bounded semialgebraic functions. In this work we compute the size of the fibers of the spectral maps and induced by the inclusion of a semialgebraic subset N of M. The ring can be understood as the localization of at the multiplicative subset of those bounded semialgebraic functions on M with empty zero set. This provides a natural inclusion that reduces both problems above to an analysis of the fibers of the spectral map . If we denote , it holds that the restriction map is a homeomorphism. Our problem concentrates on the computation of the size of the fibers of at the points of Z. The size of the fibers of prime ideals “close” to the complement provides valuable information concerning how N is immersed inside M. If N is dense in M, the map is surjective and the generic fiber of a prime ideal contains infinitely many elements. However, finite fibers may also appear and we provide a criterium to decide when the fiber is a finite set for . If such is the case, our procedure allows us to compute the size s of . If in addition N is locally compact and M is pure dimensional, s coincides with the number of minimal prime ideals contained in .     

Positive solution of singularly perturbed Dirichlet problem with singularities

A class of singularly perturbed boundary value problem with singularities is considered. Introducing the stretched variables, the boundary layer corrective terms near x = 0 and x = 1 are constructed. Under suitable conditions, by using the theory of differential inequalities the existence and asymptotic behavior of solution for boundary value problem are proved, uniformly valid asymptotic expansion of solution with boundary layers are obtained,     

A family of permitted trigonometric thin sets

We introduce the notion of perfectly measure zero sets and prove that every perfectly measure zero set is permitted for the families of all pseudo-Dirichlet sets, N-sets, A-sets and N-sets. In particular this means that these families of trigonometric thin sets are closed under adding sets of cardinality less than the additivity of Lebesgue measure.

     

Lipschitz泛函的本质临界点

本文指出Ｂａｎａｃｈ空间中Ｃ^1－0（即局部Ｌｉｐｓｃｈｉｔｚ）泛函的Ｃｌａｒｋｅ－临界点一般不具有在Ｃ^1－0局部坐标变换下的不变性。据此提出了Ｃ^1－0泛函的本质临界点的概念，它能适应研究Ｃ^1－0流形上的Ｃ^1－0泛函的临界点的需要．还给出了有关本质临界点的几个结果。     

Two examples of surfaces with normal crossing singularities

This note gives two examples of surfaces with normal crossing singularities.In the first example the canonical ring is not finitely generated.In the second,the canonical line bundle is not ample but its pull back to the normalization is ample.The latter answers in the negative a problem left unresolved in Ⅲ.2.6.2 of lments de gometrie algbrique,1961,and raised again by Viehweg.     

非线性Lipschitz算子的一个特征不变量及其应用

本文通过推广有界线性算子对偶到非线性Lipschitz算子的方法,将谱半径的概念推广到非线性情形,从而得到一个有关非线性Lipschitz算子的特征数．作为应用,本文在一定条件下证明:非线性离散系统的收敛性可由算子T在各点处的．Jacobi矩阵谱半径确定,从而部分地证明LaSalle提出的一个公开性猜想．     

Removable isolated singularities of solutions to the weighted p‐Laplacian with singular convection

This paper is concerned with the removability of isolated singularities for the weighted p‐Laplacian with singular convection. Critical singular exponents included in diffusion and convection are exactly determined. Copyright © 2012 John Wiley & Sons, Ltd.     

The probability of choosing primitive sets

We generalize a theorem of Nymann that the density of points in Zd that are visible from the origin is 1/ζ(d), where ζ(a) is the Riemann zeta function . A subset S⊂Zd is called primitive if it is a Z-basis for the lattice Zd∩spanR(S), or, equivalently, if S can be completed to a Z-basis of Zd. We prove that if m points in Zd are chosen uniformly and independently at random from a large box, then as the size of the box goes to infinity, the probability that the points form a primitive set approaches 1/(ζ(d)ζ(d−1)?ζ(d−m+1)).     

Characterizations of strictly convex sets by the uniqueness of support points

Abstract

This short paper characterizes strictly convex sets by the uniqueness of support points (such points are called unique support points or exposed points) under appropriate assumptions. A class of so-called regular sets, for which every extreme point is a unique support point, is introduced. Closed strictly convex sets and their intersections with some other sets are shown to belong to this class. The obtained characterizations are then applied to set-valued maps and to the separation of a convex set and a strictly convex set. Under suitable assumptions, so-called set-valued maps with path property are characterized by strictly convex images of the considered set-valued map.     

Semigroups of mappings with rigid Lipschitz constant

It is shown that two well-known uniformly fixed point free lipschitzian semigroups of mappings have minimal Lipschitz constant on the positive part of the unit ball of . This implies that a question raised by T. Kuczumow has a negative answer.

     

A note on non-support points, negligible sets, Gâteaux differentiability and Lipschitz embeddings

This paper first presents a characterization of three classes of negligible closed convex sets (i.e., Gauss null sets, Aronszajn null sets and cube null sets) in terms of non-support points; then gives a generalization of Gâteaux differentiability theorems of Lipschitz mapping from open sets to those closed convex sets admitting non-support points; and as their application, finally shows that a closed convex set in a separable Banach space X can be Lipschitz embedded into a Banach space Y with the Radon–Nikodym property if and only if the closure of its linear span is linearly isomorphic to a closed subspace of Y.     

Positive solutions of non‐positone Dirichlet boundary value problems with singularities in the phase variables

The paper presents existence results for positive solutions of the differential equations x ″ + μh (x) = 0 and x ″ + μf (t, x) = 0 satisfying the Dirichlet boundary conditions. Here μ is a positive parameter and h and f are singular functions of non‐positone type. Examples are given to illustrate the main results. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Descriptive properties of the set of exposed points of compact convex sets in

We construct a compact convex subset of such that the set of its exposed points is not the intersection of an set and a set. The existence of such a set answers a question posed by G. Choquet, H.H. Corson and V.L. Klee.

     

The number of translates of a closed nowhere dense set required to cover a Polish group

For a Polish group let be the minimal number of translates of a fixed closed nowhere dense subset of required to cover . For many locally compact this cardinal is known to be consistently larger than which is the smallest cardinality of a covering of the real line by meagre sets. It is shown that for several non-locally compact groups . For example the equality holds for the group of permutations of the integers, the additive group of a separable Banach space with an unconditional basis and the group of homeomorphisms of various compact spaces.     

Boundedness of multilinear singular integrals on central Morrey spaces with variable exponents

We prove the boundedness for a class of multi-sublinear singular integral operators on the product of central Morrey spaces with variable exponents. Based on this result, we obtain the boundedness for the multilinear singular integral operators and two kinds of multilinear singular integral commutators on the above spaces.