## Abstract

If in the right-hand sides of given differential equations occur discontinuities in the state variables, then the natural notion of a solution is the one in the sense of Filippov. In our paper, we will consider this type of solutions for vector Dirichlet problems. The obtained theorems deal with the existence and localization of Filippov solutions, under effective growth restrictions. Two illustrative examples are supplied.

## Abstract

We associate to some simplest quartic fields a family of elliptic curves that has rank at least three over ℚ(*m*). It is given by the equation

Employing canonical heights we show the rank is in fact at least three for all *m*. Moreover, we get a parametrized infinite family of rank at least four. Further, the integral points on the curve *E _{m}* are discussed and we determine all the integral points on the original quartic model when the rank is three. Previous work in this setting studied the elliptic curves associated with simplest quartic fields of ranks at most two along with their integral points (see [2, 3]).

## Abstract

If the face-cycles at all the vertices in a map are of same type then the map is said to be a semi-equivelar map. There are eleven types of semi-equivelar maps on the torus. In 1972 Altshuler has presented a study of Hamiltonian cycles in semi-equivelar maps of three types {3^{6}}, {4^{4}} and {6^{3}} on the torus. In this article we study Hamiltonicity of semi-equivelar maps of the other eight types {3^{3}, 4^{2}}, {3^{2}, 4^{1}, 3^{1}, 4^{1}}, {3^{1}, 6^{1}, 3^{1}, 6^{1}}, {3^{4}, 6^{1}}, {4^{1}, 8^{2}}, {3^{1}, 12^{2}}, {4^{1}, 6^{1}, 12^{1}} and {3^{1}, 4^{1}, 6^{1}, 4^{1}} on the torus. This gives a partial solution to the well known Conjecture that every 4-connected graph on the torus has a Hamiltonian cycle.

## Abstract

In this paper, we present numerous refinements of the Young inequality by the Kantorovich constant. We use these improved inequalities to establish corresponding operator inequalities on a Hilbert space and some new inequalities involving the Hilbert-Schmidt norm of matrices. We also give some refinements of the following Heron type inequality for unitarily invariant norm |||⋅||| and *A*, *B*, *X* ∈ *M _{n}*(ℂ):

where *r*
_{0} = min{*ν*, 1 – *ν*}.

## Abstract

The main aim of this paper is to study the fifth Hankel determinant for the class of functions with bounded turnings. The results are also investigated for 2-fold symmetric and 4-fold symmetric functions.

## Abstract

The problem of iterated partial summations is solved for some discrete distributions defined on finite supports. The power method, usually used as a computational approach to the problem of finding matrix eigenvalues and eigenvectors, is in some cases an effective tool to prove the existence of the limit distribution, which is then expressed as a solution of a system of linear equations. Some examples are presented.

## Abstract

The question as to the number of sets obtainable from a given subset of a topological space using the operators derived by composing members of the set {*b*, *i*, ∨, ∧}, where *b*, *i*, ∨ and ∧ denote the closure operator, the interior operator, the binary operators corresponding to union and intersection, respectively, is called the Kuratowski {*b*, *i*, ∨, ∧}-problem. This problem has been solved independently by Sherman [21] and, Gardner and Jackson [13], where the resulting 34 plus identity operators were depicted in the Hasse diagram. In this paper we investigate the sets of fixed points of these operators. We show that there are at most 23 such families of subsets. Twelve of them are the topology, the family of all closed subsets plus, well known generalizations of open sets, plus the families of their complements. Each of the other 11 families forms a complete complemented lattice under the operations of join, meet and negation defined according to a uniform procedure. Two of them are the well known Boolean algebras formed by the regular open sets and regular closed sets, any of the others in general need not be a Boolean algebras.

## Abstract

The goal of this paper is to propose a modification of Lupaş-Jain operators based on a function *ρ* having some properties. Primarily, the convergence of given operators in weighted spaces is discussed. Then, order of approximation via weighted modulus of continuity is computed for these operators. Further, Voronovskaya type theorem in quantitative form is taken into consideration, as well. Ultimately, some graphical results that illustrate the convergence of investigated operators to *f* are given.

## Abstract

In this paper, two new analogues of the Hilbert matrix with four-parameters have been introduced. Explicit formulæ are derived for the *LU*-decompositions and their inverses, and the inverse matrices of these analogue matrices.