In this paper, we shall study the eigenvalue problem of a singular quasilinear elliptic equation. We will show that many results about the eigenvalues and eigenfunctions in the non-singular case can be extended to the more general singular case, e.g., the first eigenvalue λ is associated to a...

Spot prices of electricity and other energy commodities are often modeled by multifactor stochastic processes. This poses a problem of estimating models' parameters based on historical data, i.e. calibrating them to markets. Here we show how a traditional tool of Kalman Filters can be...

Yager considered the problem of maximizing an OWA aggregation of a group of variables that are interrelated and constrained by a collection of linear inequalities and he showed how this problem can be modelled as a mixed integer linear programming problem. In this short communication we show a...

Given 2, we establish a good upper bound for the number of multivariate polynomials (with as many variables and with as large degree as we wish) with integer coefficients mapping the “cube” with real coordinates from [−] into [−]. This directly translates to a nice statement in logic...

We present some examples of mathematically natural nonrecursive sets of integers and relations on integers by combining results from Part 1, recursion theory, and from the negative solution to Hilbert's 10th Problem ([3], [1] and [2])

Wo considor tho problem of approximating tho b-chromatic number of a graph. We show that there is no constant > 0 for which this problem can be approximated within a factor 120/113 — in polynomial time, unless P = NP. This is the first hardness result for approximating the b-chromatic number

We discuss congruences for stochastic relations, stressing the equivalence of smooth equivalence relations and countably generated σ-algebras. Factor spaces are constructed for congruences and for morphisms. Semi-pullbacks are needed when investigating the interplay between congruences and...

We present several results on exact controllability for linear and nonlinear parabolic equations, both when the distributed control is acting linearly or nonlinearly on the whole domain. As a very particular case, we extend some recent works by means of a simpler constructive approach....