Some remarks on good sets

It is shown that (1) if a good set has finitely many related components, then they are full, (2) loops correspond one-to-one to extreme points of a convex set. Some other properties of good sets are discussed.     

Geometry of good sets in<Emphasis Type="Italic">n</Emphasis>-fold Cartesian product

We propose here a multidimensional generalisation of the notion of link introduced in our previous papers and we discuss some consequences for simplicial measures and sums of function algebras.     

Several remarks on star-shaped sets

Questions related to the properties of unions and intersections of star-shaped compact subsets of finite-dimensional spaces are considered. Translated fromMatematicheskie Zametki, Vol. 65, No. 4, pp. 511–519, April, 1999.     

Some remarks on the intersection of embedded sets

We study certain connections between a parameter characterizing the intersection of embedded sets and the Jung constant. We also define the critical value of the parameter for a certain product space and prove that, in reflexive spaces, the intersection of embedded sets is nonempty for the critical value of the parameter.     

When isf(x1, x2, ..., xn) =u1(x1) +u2(x2) + ... +un(xn)?

We discuss subsetsS of ℝⁿ such that every real valued functionf onS is of the formf(x₁, x₂, ..., x_n) =u ₁(x₁) +u ₂(x₂) +...+u _n(x_n), and the related concepts and situations in analysis.     

Some remarks on the genericity of unique range sets for meromorphic functions

In this paper we relate the study of unique range sets for meromorphic functions (URSM) with the hyperbolic hypersurfaces and give some remarks on the genericity of unique range sets for meromorphic functions.     

Some remarks on totally imperfect sets

We prove the following two theorems.

Theorem 1. Let be a strongly meager subset of . Then it is dual Ramsey null.

We will say that a -ideal of subsets of satisfies the condition iff for every , if

then .

Theorem 2. The -ideals of perfectly meager sets, universally meager sets and perfectly meager sets in the transitive sense satisfy the condition .

     

Some results on projection of planar sets

In this paper we define certain types of projections of planar sets and study some properties of such projections.     

Some remarks on the study of good contractions

LetX be a complex projective variety with log terminal singularities admitting an extremal contraction in terms of Minimal Model Theory, i.e. a projective morphism φ:X→Z onto a normal varietyZ with connected fibers which is given by a (high multiple of a) divisor of the typeK _x+rL, wherer is a positive rational number andL is an ample Cartier divisor. We first prove that the dimension of anu fiberF of φ is bigger or equal to (r-1) and, if φ is birational, thatdimF≥r, with the equalities if and only ifF is the projective space andL the hyperplane bundle (this is a sort of “relative” version of a theorem of Kobayashi-Ochiai). Then we describe the structure of the morphism φ itself in the case in which all fibers have minimal dimension with the respect tor. If φ is a birational divisorial contraction andX has terminal singularities we prove that φ is actually a “blow-up”.     

Actions of Boolean rings on sets

LetB be a Boolean ring (with 1),S a sheaf of sets on the Stone space Spec(B), andS the set of global sections of S. For everya B ands, t S, leta(s, t) denote the element ofS which agrees withs on the support ofa, and witht elsewhere.We set down identities satisfied by this ternary operationB×S×SS (involving also the Boolean operations ofB). For a fixed Boolean ringB, we call a setS given with a ternary operation satisfying these identities aBset. The above construction is shown to give a functorial equivalence between sheaves of setsS on Spec(B) with nonempty sets of global sections, and nonemptyB-setsS. For any setA, the bounded Boolean powerA[B]^* is the freeB-set onA. The varieties ofB-sets, asB ranges over all Boolean rings, constitute (together with one trivial variety) the least nontrivial hypervariety of algebras, in the sense of W. Taylor.This work was done while the author was partly supported by NSF contract DMS 85-02330.Presented by R. S. Pierce.     

The omega limit sets of subsets in a metric space

In this paper, we discuss the properties of limit sets of subsets and attractors in a compact metric space. It is shown that the -limit set (Y) of Y is the limit point of the sequence {(Cl Y) [i, )}_i=1 in 2^X and also a quasi-attractor is the limit point of attractors with respect to the Hausdorff metric. It is shown that if a component of an attractor is not an attractor, then it must be a real quasi-attractor.This paper was completed while the author was visiting the Academy of Mathematics and Systems, Chinese Academy of Sciences. The author was supported by the National Science Foundation of China (Grant No. 10461003).     

Some remarks on the dynamics of cell membranes

Motivated by the desire to model the entry of 1,25D into a cell by receptor mediated endocytosis, we have formulated the problem as the dynamics of a bilayer membrane. We have discussed setting the problem as a variational problem using the Helfrich modeling of the bilayer in terms of the free energy. Using a Lagrangian formulation we arrive at the Euler–Lagrange equations for the system. The model we have used depends on the amount of reagent in the neighborhood of the upper membrane. The problem thereby reduces to a moving boundary problem, which is dependent on a diffusion equation for a region changing with time. In order to solve this problem we seek the correct Neumann function for this altered. This is accomplished by deriving a Hadamard variational formula for the diffusion equation. We also offer an iterative procedure for solving this non-linear problem.     

Contribution to application of energy measure of fuzzy sets

The works of De Luca & Termini continued by, for example, Knopfmacher, Loo and Gottwald, are the most important on the topic of determination of measures of fuzzy sets. The matter is to evaluate how fuzzy a fuzzy set is. There are two general concepts of measures of fuzzy set, i.e. entropy and energy measures.We show that the special kind of energy measure is better suited than the entropy kind of measure in many practical situations.Applications of the use of energy measure discussed in detail include decision making, fuzzy process control and prediction in fuzzy systems.     

Some results on topical functions and upward sets

The purpose of this paper is to introduce and discuss the concept of topical functions on upward sets.We give characterizations of topical functions in terms of upward sets.     

关于吸引子的某些性质

Conley在[1]中讨论拓扑空间X上动力系统的吸引子——排斥子对时,给出了吸引子存在的两个充分条件．本文证明这两个条件实际上也是必要的,进而证明Conley所定义的吸引子是渐近稳定的．     

近似凸集的某些性质

主要研究了两类近似凸集的关系和性质.首先,举例说明两类近似凸集没有相互包含关系.其次,在近似凸集(nearly convex)条件下,证明了在一定条件下函数上图是近似凸集与凸集的等价关系.同时,考虑了近似凸函数与函数上图是近似凸集的等价刻画、近似凸函数与函数水平集是近似凸集的必要性,并用例子说明近似凸函数与函数水平集是...     

Some remarks on the geodetic number of a graph

A set of vertices D of a graph G is geodetic if every vertex of G lies on a shortest path between two not necessarily distinct vertices in D. The geodetic number of G is the minimum cardinality of a geodetic set of G.We prove that it is NP-complete to decide for a given chordal or chordal bipartite graph G and a given integer k whether G has a geodetic set of cardinality at most k. Furthermore, we prove an upper bound on the geodetic number of graphs without short cycles and study the geodetic number of cographs, split graphs, and unit interval graphs.