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In this chapter we discuss the problem of establishing determinantal criteria for when a matrix is totally positive or strictly totally positive. Totally different criteria will be discussed in the next chapter on variation diminishing.
In Section 2.1 we prove Fekete's Lemma and some of its consequences. The most notable thereof is Theorem 2.3, which states that for a matrix to be strictly totally positive it suffices to prove that all its minors composed of the first k rows and k consecutive columns and all its minors composed of the first k columns and k consecutive rows are strictly positive for all possible k. We apply the results of Section 2.1 in Section 2.2, where we prove that strictly totally positive matrices are dense in the class of totally positive matrices, and provide proofs of Propositions 1.9 and 1.10 from Chapter 1.
In Section 2.3 we discuss triangular matrices, detail determinantal criteria for when such matrices are totally positive, and in Section 2.4 we consider the LDU-factorization of strictly totally positive and totally positive matrices. We will return to the study of factorizations of totally positive matrices in Chapter 6. In Section 2.5 we consider determinantal criteria for when a matrix is totally positive. The results are nowhere near as elegant as those valid for strictly totally positive matrices.
In Section 2.6 we prove a recent surprising and beautiful result of O. M. Katkova and A. M. Vishnyakova (completing work initiated by T. Craven and G. Csordas).
In this chapter we review the spectral properties of totally positive matrices. A strictly totally positive matrix has positive, simple eigenvalues and the associated eigenvectors possess an intricate structure. Such is not the case for totally positive matrices. However, there is an intermediate set of matrices with the same spectral properties as strictly totally positive matrices. These matrices are called oscillation matrices. They shall be discussed in Section 5.1. In Section 5.2 we present the Gantmacher–Krein Theorem (Theorem 5.3) and give two quite different proofs thereof. This theorem contains the main spectral properties of oscillation matrices. In Section 5.3 we consider eigenvalues of the principal submatrices of such matrices and study their behaviour. We study in more detail the properties of eigenvectors of oscillation matrices in Section 5.4. Finally, in Section 5.5, we look at how the eigenvalues of oscillation matrices vary as functions of the elements of the matrix.
Oscillation matrices
Oscillation matrices are a class of matrices intermediary between totally positive and strictly totally positive matrices. They share the eigenvalue and eigenvector structure of strictly totally positive matrices.
Definition 5.1 An n × n matrix A is said to be an oscillation matrix if A is totally positive and some power of A is strictly totally positive.
Importantly, there are relatively simple criteria for determining if a totally positive matrix is an oscillation matrix.
Let C be a non-empty closed convex subset of a reflexive and strictly convex Banach space E which also has a weakly continuous duality map Jφ(x) with the gauge φ. Let S and T be non-expansive mappings from C into itself such that F = F(S) ∩ F(T) ≠ ∅. Let {αn} and {βn} be sequences in (0, 1). Let {xn} be a sequence defined bywhere u ∈ C is a given point. Assume that the following restrictions imposed on the control sequences are satisfied:
Then the sequence {xn} converges strongly to x* ∈ F, where x* = Q(u) and Q: C → F is the unique sunny non-expansive retraction from C onto F.
In this paper, we prove that any Zinbiel algebra can be endowed with the structure of commutative algebra with divided powers. We introduce the notion of universal enveloping Zinbiel algebra of a commutative algebra with divided powers algebras. We prove that the free divided powers algebra on a free module M, is the divided powers sub-algebra generated by M, of the divided powers algebra induced by the free Zinbiel algebra on M. Finally, we construct a basis for the enveloping Zinbiel algebra.
Let R be a commutative ring with non-zero identity and M be a unitary R-module. Let (M) be the set of all submodules of M, and φ: (M) → (M) ∪ {∅} be a function. We say that a proper submodule P of M is a prime submodule relative to φ or φ-prime submodule if a ∈ R and x ∈ M, with ax ∈ P ∖ φ(P) implies that a ∈(P :RM) or x ∈ P. So if we take φ(N) = ∅ for each N ∈ (M), then a φ-prime submodule is exactly a prime submodule. Also if we consider φ(N) = {0} for each submodule N of M, then in this case a φ-prime submodule will be called a weak prime submodule. Some of the properties of this concept will be investigated. Some characterisations of φ-prime submodules will be given, and we show that under some assumptions prime submodules and φ1-prime submodules coincide.
In this paper we consider a non-linear periodic problem driven by the scalar p-Laplacian and with a non-smooth potential. We assume that the multi-valued right-hand-side non-linearity exhibits an asymmetric behaviour at ±∞ and crosses a finite number of eigenvalues as we move from −∞ to +∞. Using a variational approach based on the non-smooth critical-point theory, we show that the problem has at least two non-trivial solutions, one of which has constant sign. For the semi-linear (p = 2), smooth problem, using Morse theory, we show that the problem has at least three non-trivial solutions, again one with constant sign.
This paper deals with the following degenerate and singular equationwith non-local source and absorption. The existence of a unique classical non-negative solution is established and the sufficient conditions for the solution that exists globally or blows up in finite time are obtained.
Our aim in this paper is to deal with Sobolev's embeddings for Sobolev–Orlicz functions with ∇u ∈ Lp(·) logLq(·)(Ω) for Ω ⊂ n. Here p and q are variable exponents satisfying natural continuity conditions. Also the case when p attains the value 1 in some parts of the domain is included in the results.
In this paper we introduce -non-cosingular modules, dual Baer modules and -modules. We prove that a module M is lifting and -non-cosingular if and only if it is a dual Baer and -module. Rings for which all modules are dual Baer are precisely determined. We also give a necessary condition for a finite direct sum of dual Baer modules to be dual Baer.
In this book, first published in 2003, the reader is provided with a tour of the principal results and ideas in the theories of completely positive maps, completely bounded maps, dilation theory, operator spaces and operator algebras, together with some of their main applications. The author assumes only that the reader has a basic background in functional analysis, and the presentation is self-contained and paced appropriately for graduate students new to the subject. Experts will also want this book for their library since the author illustrates the power of methods he has developed with new and simpler proofs of some of the major results in the area, many of which have not appeared earlier in the literature. An indispensable introduction to the theory of operator spaces for all who want to know more.
We study the behaviour of the steady-state voltage potentials in a material composed of a two-dimensional object surrounded by a rough thin layer and embedded in an ambient medium. The roughness of the layer is supposed to be ϵ-periodic, ϵ being the magnitude of the mean thickness of the layer. For ϵ tending to zero, we determine approximate transmission conditions in order to replace the rough thin layer by these conditions on the boundary of the interior material. This paper extends the previous works (Poignard, 2009, Math. Meth. Appl. Sci., vol. 32, pp. 435–453; Poignard et al., 2008, IEEE Trans. Magnet., vol. 44, no. 6, pp. 1154–1157) of the third author, which deal with smooth thin layers.
The aim of this book is to unite the seemingly disparate topics of Clifford algebras, analysis on manifolds and harmonic analysis. The authors show how algebra, geometry and differential equations all play a more fundamental role in Euclidean Fourier analysis than has been fully realized before. Their presentation of the Euclidean theory then links up naturally with the representation theory of semi-simple Lie groups. By keeping the treatment relatively simple, the book will be accessible to graduate students, yet the more advanced reader will also appreciate the wealth of results and insights made available here.