in this paper, at rst for a given set of real or complex numbers  with nonnegative summation, we introduce some special conditions that with them there is no nonnegative tridiagonal matrix in which  is its spectrum. in continue we present some conditions for existence such nonnegative tridiagonal matrices.

In this note, we consider a family of iterative formula for computing the weighted Minskowski inverses A ⊕ M,N in Minskowski space, and give two kinds of iterations and the necessary and sufficient conditions of the convergence of iterations. Keywords—iterative method, the Minskowski inverse, A ⊕ M,N inverse.

Experiments were performed to reveal some of the computational properties of the human motor memory system. We show that as humans practice reaching movements while interacting with a novel mechanical environment, they learn an internal model of the inverse dynamics of that environment. Subjects show recall of this model at testing sessions 24 hours after the initial practice. The representatio...

Let X be a smooth quadric of dimension 2m in P C and let Y, Z ⊂ X be subvarieties both of dimension m which intersect transversely. In this paper we give an algorithm for computing the intersection points of Y ∩ Z based on a homotopy method. The homotopy is constructed using a C∗-action on X whose fixed points are isolated, which induces Bialynicki-Birula decompositions of X into locally closed...

A lattice P is transferable for a class of lattices K if whenever P can be embedded into the ideal lattice IK of some K ∈ K, then P can be embedded into K. There is a rich theory of transferability for lattices. Here we introduce the analogous notion of MacNeille transferability, replacing the ideal lattice IK with the MacNeille completion K. Basic properties of MacNeille transferability are de...

Let lK be a commutative field and (P, +) be a uniquely 2-divisible group (not necessarily abelian). We characterize all functions T: IK -+ P such that the Cauchy difference T(s+ t) T(t) T(s) depends only on the product st for all s, t E ~{. Further, we apply this result to describe solutions of the functional equation F(s + t) = K(st) 0 H(s) 0 G(t), where the unknown functions F, K, H, G map th...

Most of the methods among the inverse regression literature rely on a slicing of the range of the response variable. Theoretical results are usually shown assuming that (i) the slices are fixed while in practice estimators are constructed with (ii) random slices that contain the same number of observations. In this paper we obtain the asymptotic normality in the case where the slices contains t...

the aim of this paper is to study semigroups possessing $e$-regular elements, where an element $a$ of a semigroup $s$ is {em $e$-regular} if $a$ has an inverse $a^circ$ such that $aa^circ,a^circ a$ lie in $ esubseteq e(s)$. where $s$ possesses `enough' (in a precisely defined way) $e$-regular elements, analogues of green's lemmas and even of green's theorem hold, where green&apos...