An application of continuous fuzzy multifunctions

In this paper, the upper and lower δ-continuous multifunctions in fuzzy setting have been presented as a strong form and an application of fuzzy continuous multifunctions. Certain characterizations and several properties of these fuzzy multifunctions along with their mutual relationships are obtained. Attempts are also made to correlate this new class with the corresponding known types of fuzzy multifunctions. Also, applicability of the above new concepts to superstrings and space time could be probably possible in the near future.     

On multifunctions

In this paper, we introduce and study γ-continuous multifunctions as a generalization of quasi-continuous multifunctions due to Popa in 1985 and precontinuous multifunctions due to Popa in 1988. Some characterizations and several properties concerning upper (lower) γ-continuous multifunctions are obtained. The relationships between upper (lower) γ-continuous multifunctions and some known concepts are also discussed.     

Error bounds on the power method for determining the largest eigenvalue of a symmetric, positive definite matrix

Let A be a positive definite, symmetric matrix. We wish to determine the largest eigenvalue, λ₁. We consider the power method, i.e. that of choosing a vector v₀ and setting v_k = A^kv₀; then the Rayleigh quotients R_k = (Av_k, v_k)/(v_k, v_k) usually converge to λ₁ as k → ∞ (here (u, v) denotes their inner product). In this paper we give two methods for determining how close R_k is to λ₁. They are both based on a bound on λ₁ − R_k involving the difference of two consecutive Rayleigh quotients and a quantity ω_k. While we do not know how to directly calculate ω_k, we can given an algorithm for giving a good upper bound on it, at least with high probability. This leads to an upper bound for λ₁ − R_k which is proportional to (λ₂/λ₁)^2k, which holds with a prescribed probability (the prescribed probability being an arbitrary δ > 0, with the upper bound depending on δ).     

On super continuous multifunctions

We define upper (lower) super continuous multifunctions and obtain some characterizations and basic properties of such a multifunction. Also some relationships between the concept of super continuity and known concepts of continuity and strongly Θ-continuity are given. This revised version was published online in June 2006 with corrections to the Cover Date.     

Weakly upper Lipschitz multifunctions and applications in parametric optimization

The main purpose of this paper is to report on our studies of the weak upper Lipschitz and weak -upper Lipschitz continuities of multifunctions. Comparisons with other related Lipschitz-type continuities and calmness are given. When the concept of the weak upper Lipschitz continuities is applied to the special cases of constraint multifunctions, such as ones defined by a systems of equalities and inequalities or by a generalized equation we obtain the equivalent conditions with linear functional error bounds. Some results on the perturbation and penalty issues in parametric optimization problems are obtained under weak upper Lipschitz continuity assumptions on the constraint multifunctions. We also discuss the weak -upper Lipschitz continuity of a inverse subdifferential.Mathematics Subject Classification (2000): 49J52, 49J53, 90C25Acknowledgement The author thanks the associate editor and the referees for their helpful suggestions and comments.     

On L(d,1)-labelings of graphs

Given a graph G and a positive integer d, an L(d,1)-labeling of G is a function f that assigns to each vertex of G a non-negative integer such that if two vertices u and v are adjacent, then |f(u)−f(v)|d; if u and v are not adjacent but there is a two-edge path between them, then |f(u)−f(v)|1. The L(d,1)-number of G, λ_d(G), is defined as the minimum m such that there is an L(d,1)-labeling f of G with f(V){0,1,2,…,m}. Motivated by the channel assignment problem introduced by Hale (Proc. IEEE 68 (1980) 1497–1514), the L(2,1)-labeling and the L(1,1)-labeling (as d=2 and 1, respectively) have been studied extensively in the past decade. This article extends the study to all positive integers d. We prove that λ_d(G)Δ²+(d−1)Δ for any graph G with maximum degree Δ. Different lower and upper bounds of λ_d(G) for some families of graphs including trees and chordal graphs are presented. In particular, we show that the lower and the upper bounds for trees are both attainable, and the upper bound for chordal graphs can be improved for several subclasses of chordal graphs.     

Openness properties of real multifunctions on some connected spaces

Real multifunctions on connected spaces are studied. In the class of connected and locally compact metrizable spaces structural characterizations are shown of such ones on which each either lower or upper semicontinuous real multifunction with connected values (and possibly with boundary point-inverses) is either almost open or pseudo-almost open. Many related results are obtained.     

The deviation, density, and depth of partially ordered sets

Let P be a poset, and let γ be a linear order type with |γ| ≥ 3. The γ-deviation of P, denoted by γ-dev P, is defined inductively as follows: (1) γ-dev P=0, if P contains no chain of order type γ; (2) γ-dev P = , if γ-dev P and each chain C of type γ in P contains elements a and b such that a<b and [a, b] as an interval of P has γ-deviation <. There may be no ordinal such that γ-dev P = ; i.e., γ-dev P does not exist. A chain is γ-dense if each of its intervals contains a chain of order type γ. If P contains a γ-dense chain, then γ-dev P fails to exist. If either (1) P is linearly ordered or (2) a chain of order type γ does not contain a dense interval, then the converse holds. For an ordinal ξ, a special set S(ξ) is used to study ω_ξ-deviation. The depth of P, denoted by δ(P) is the least ordinal β that does not embed in P^*. Then the following statements are equivalent: (1) ω_ξ-dev P does not exist; (2) S(ξ) embeds in P; and (3) P has a subset Q of cardinality _ξ such that δ(Q^*) = ω_{ξ + 1}. Also ω_ξ-dev P = <ω_{ξ + 1} if and only if |δ(P^*)|_ξ; if these equivalent conditions hold, then ω^β_ξ < δ(P^*) ≤ ω ^{+ 1}_ξ for all β < . Applications are made to the study of chains of submodules of a module over an associative ring.     

Torsion Pairs in Stable Categories

Let 𝒞 be a triangulated category. When ω is a functorially finite subcategory of 𝒞, Jøtrgensen showed that the stable category 𝒞/ω is a pretriangulated category. A pair (𝒳, 𝒴) of subcategories of 𝒞 with ω ? 𝒳 ∩ 𝒴 gives rise to a pair (𝒳/ω, 𝒴/ω) of subcategories of 𝒞/ω. In this article, we find conditions for (𝒳/ω, 𝒴/ω) to be a torsion pair in terms of properties of the pair (𝒳, 𝒴). In particular, we obtain necessary and sufficient conditions for (𝒳/ω, 𝒴/ω) to be a torsion pair in the stable category 𝒞/ω when τω = ω, where τ is the Auslander–Reiten translation.     

Distributional chaos for triangular maps

In this paper we exhibit a triangular map F of the square with the following properties: (i) F is of type 2^∞ but has positive topological entropy; we recall that similar example was given by Kolyada in 1992, but our argument is much simpler. (ii) F is distributionally chaotic in the wider sense, but not distributionally chaotic in the sense introduced by Schweizer and Smítal [Trans. Amer. Math. Soc. 344 (1994) 737]. In other words, there are lower and upper distribution functions Φ_xy and Φ_xy^* generated by F such that Φ_xy^*≡1 and Φ_xy(0₊)<1, and no distribution functions Φ_uv, and Φ_uv^* such that Φ_uv^*≡1 and Φ_uv(t)=0 whenever 0<t<ε, for some ε>0. We also show that the two notions of distributional chaos used in the paper, for continuous maps of a compact metric space, are invariants of topological conjugacy.     

A new upper bound for the isoperimetric number of deBruijn Networks

Delorme and Tillich found an upper bound and a lower bound for the isoperimetric number iⁿ(d) of deBruijn Networks over the alphabet {0,1,…,d − 1} using eigenvalue techniques (see [1]). We improve their upper bound for iⁿ(d) and give constructions for the sets of vertices of the deBruijn Network, which lead to our bound.     

Some topological problems in multifunctions theory

The problem of upper semicontinuity of graph-closed multifunctions is considered. Also, several recent results on extension of multifunctions are presented.     

L-nets and Weakly Continuous L-fuzzy Multifunctions

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Upper semicontinuity of set-valued functions

Various types of upper semcontinuity properties for set-valued functions have been used in the past to obtain closure and lower closure theorems in optimal control theory as well as selection theorems and fixed-point theorems in topology. This paper unifies these various concepts by using semiclosure operators, extended topologies, and lattice theoretic operations and obtains general closure theorems. In addition, analytic criteria are given for this generalized upper semicontinuity. In particular, set-valued functions which are maximal in terms of certain properties (e.g., maximal monotone multifunctions) are shown to be necessarily upper semicontinuous.     

Continuity of lower envelopes

The purpose of the paper is to give a complete characterization of the continuity of lower envelopes in the infinite dimensional spaces. The characterization of upper or lower semicontinuity of envelopes, when stated in the language of multifunctions, has a dual geometric character which depends on the upper or lower semicontinuity of the corresponding multifunction.     

On a class of fractals: the constructive structure

In the present paper, we consider the following generalization of Besicovitch functions. Let {λ_n} satisfy Hadamard condition, write

f(t)=∑^∞_n=1a_ncosλ_nt.

We are interested in the intrinsic relationship among the coefficients {a_n}, the modulus of continuity of f and the upper Box dimension of graph of f. Especially, constructive structure of the function f which can be deduced from the (upper) Box dimension is a very interesting subject, and is hardly ever touched upon as far as we are aware.     

Toward A geometric theory of minimax equalities

We present new ideas and concepts in minimax equalities. Two important classes of multifunctions will be singled out, the Weak Passy-Prisman multifunctions and multifunctions possessing the finite simplex property. To each class of multifunctions corresponds a class of functions. We obtain necessary and sufficient conditions for a multifunction to have the finite intersection property, and necessary and sufficient conditions for a function to be a minimax function. All our results specialize to sharp improvements of known theorems, Sion, Tuy, Passy-Prisman, Flåm-Greco. One feature of our approach is that no topology is required on the space of the maximization variable. In a previous paper [6] we presented a “method of reconstruction of polytopes” from a given family of subsets, this in turn lead to a “principle of reconstruction of convex sets” Theorem 3, which plays a major role in this paper. Our intersection theorems bear no obvious relationship to other results of the same kind, like K.K.M. or other more elementary approaches based on connectedness. We conclude our work with a remark on the role of upper and lower semicontinuous regularization in mimmax equalities     

ON A GENERALIZED MODULUS OF CONVEXITY AND UNIFORM NORMAL STRUCTURE

In this article, the authors study a generalized modulus of convexity, δ(α)(∈).Certain related geometrical properties of this modulus are analyzed. Their main result is that Banach space X has uniform normal structure if there exists ∈, 0 ≤∈≤1, such that δ(α)(1 ∈) ＞ (1 - α)∈.     

Strong approximation for cross-covariances of linear variables with long-range dependence

Suppose {_k, −∞ < k < ∞} is an independent, not necessarily identically distributed sequence of random variables, and {c_j}^∞_j=0, {d_j}^∞_j=0 are sequences of real numbers such that Σ_jc²_j < ∞, Σ_jd²_j < ∞. Then, under appropriate moment conditions on {_k, −∞ < k < ∞}, y_k Σ^∞_j=0c_jk-j, z_k Σ^∞_j=0d_jk-j exist almost surely and in ⁴ and the question of Gaussian approximation to S_[t]Σ^[t]_k=1 (y_k z_k − E{y_k z_k}) becomes of interest. Prior to this work several related central limit theorems and a weak invariance principle were proven under stationary assumptions. In this note, we demonstrate that an almost sure invariance principle for S_[t], with error bound sharp enough to imply a weak invariance principle, a functional law of the iterated logarithm, and even upper and lower class results, also exists. Moreover, we remove virtually all constraints on _k for “time” k ≤ 0, weaken the stationarity assumptions on {_k, −∞ < k < ∞}, and improve the summability conditions on {c_j}^∞_j=0, {d_j}^∞_j=0 as compared to the existing weak invariance principle. Applications relevant to this work include normal approximation and almost sure fluctuation results in sample covariances (let d_j = c_j-m for j ≥ m and otherwise 0), quadratic forms, Whittle's and Hosoya's estimates, adaptive filtering and stochastic approximation.     

ContributionsSign-balanced covering matrices

A q × n array with entries from 0, 1,…,q − 1 is said to form a difference matrix if the vector difference (modulo q) of each pair of columns consists of a permutation of [0, 1,… q − 1]; this definition is inverted from the more standard one to be found, e.g., in Colbourn and de Launey (1996). The following idea generalizes this notion: Given an appropriate δ (-[−1, 1]^t, a λq × n array will be said to form a (t, q, λ, Δ) sign-balanced matrix if for each choice C₁, C₂,…, C_t of t columns and for each choice = (₁,…,_t) Δ of signs, the linear combination ∑_j=1^t _jC_j contains (mod q) each entry of [0, 1,…, q − 1] exactly λ times. We consider the following extremal problem in this paper: How large does the number k = k(n, t, q, λ, δ) of rows have to be so that for each choice of t columns and for each choice (₁, …, _t) of signs in δ, the linear combination ∑_j=1^t _jC_j contains each entry of [0, 1,…, q t- 1] at least λ times? We use probabilistic methods, in particular the Lovász local lemma and the Stein-Chen method of Poisson approximation to obtain general (logarithmic) upper bounds on the numbers k(n, t, q, λ, δ), and to provide Poisson approximations for the probability distribution of the number W of deficient sets of t columns, given a random array. It is proved, in addition, that arithmetic modulo q yields the smallest array - in a sense to be described.