We study the problem of estimating large covariance matrices under two types of structural assumptions: (i) The covariance matrix is the summation of a low rank matrix and a sparse matrix, and we have some prior information on the sparsity pattern of the sparse matrix; (ii) The data follow a transelliptical distribution. The former structure regulates the parameter space and has its roots in di...

Spearman’s rank correlation coefficient is a nonparametric (distribution-free) rank statistic proposed by Charles Spearman as a measure of the strength of an association between two variables. It is a measure of a monotone association that is used when the distribution of data makes Pearson’s correlation coefficient undesirable or misleading. Spearman’s coefficient is not a measure of the linea...

in this paper the periodic solutions of fourth order delay differential equation of the form $ddddot{x}(t)+adddot{x}(t)+f(ddot{x}(t-tau(t)))+g(dot{x}(t-tau(t)))+h({x}(t-tau(t)))=p(t)$  is investigated. some new positive periodic criteria are given.

Let $X$ be an infinite set, equipped with a topology $tau$. In this paper we studied the relationship between $tau$, and ultrafilters on $X$. We can discovered, among other thing, some relations of the Robinson's compactness theorem, continuity and the separation axioms. It is important also, aspects of communication between mathematical concepts.

the aim of this note is to study the submajorization inequalities for $tau$-measurable operators in a semi-finite von neumann algebra on a hilbert space with a normal faithful semi-finite trace $tau$. the submajorization inequalities generalize some results due to zhang, furuichi and lin, etc..

Abstract The paper has two relatively distinct but connected goals; the first is to define notion of Padé approximation Weyl–Stiltjes transforms on an arbitrary compact Riemann surface higher genus. data consists a contour in and measure it, together with additional datum local coordinate near point divisor degree g . denominators resulting Padé-like also satisfy orthogonality relation are sect...

We prove that the filling order is quadratic for a large class of solvable groups and asymptotically quadratic for all Q-rank one lattices in semisimple groups of R-rank at least 3. As a byproduct of auxiliary results we give a shorter proof of the theorem on the nondistorsion of horospheres providing also an estimate of a nondistorsion