Spectral Analysis of a Transport Operator Arising in Growing Cell Populations

The present paper is concerned with the spectral analysis of a transport-like operator derived from a model introduced by Rotenberg describing the growth of a cell population. Each cell of this population is distinguished by its degree of maturity μ and its maturation velocity v. The biological boundaries of μ = 0 and μ = a (a > 0) are fixed and tightly coupled through mitosis. At mitosis daughter cells and mother cells are related by a general reproduction rule which covers all known biological ones. We first discuss in detail the spectrum of the streaming operator for smooth and partly smooth boundary conditions. Next, we discuss the existence and nonexistence of eigenvalues of the transport operator in the half plane {λ ∈ ℂ : Reλ > where denotes the spectral bound of the streaming operator. In particular, the strict monotonicity of the leading eigenvalue (when it exists) of the transport operator with respect to different parameters of the equation is also considered. We close the paper by describing in detail the various essential spectra of the transport operator for wide classes of collision and boundary operators.     

Operator Interpretation of Resonances Arising in Spectral Problems for 2 × 2 Operator Matrices

We consider operator matrices ${\rm{H = }}\left( {{_{B_{10} }^{A{_0}}} {_{A_{1} }^{B{_{01}}}} } \right)$ with self - adjoint entries A_i, i = 0,1, and bounded B₁₀ = B₁₀ acting in the orthogonal sum μ=μ₀ ⊕ μ₁ of Hilbert spaces μ₀ and μ₁. We are especially interested in the case where the spectrum of, say, A₁ is partly or totally embedded into the continuous spectrum of A₀ and the transfer function V₁(z) = B₁₀ where (χ - A₀)^?1 B₀₁, admits analytic continuation (as an operator - valued function) through the cuts along branches of the continuous spectrum of the entry A₀ into the unphysical sheet(s) of the spectral parameter plane. The values of χ in the unphysical sheets where M₁^?1(z) and consequently the resolvent (H - z)^?1 have poles are usually called resonances. A main goal of the present work is to find non - selfadjoint operators whose spectra include the resonances as well as to study the completeness and basis properties of the resonance eigenvectors of M₁(z) in μ₁. To this end we first construct an operator - valued function V₁(Y) on the space of operators in μ₁ possessing the property: V₁(Y)?₁ = V₁(z)?₁ for any eigenvector ?₁ of Y corresponding to an eigenvalue z and then study the equation H₁ = A₁ + V₁(H₁). We prove the solvability of this equation even in the case where the spectra of A₀ and A₁ overlap. Using the fact that the root vectors of the solutions H₁ are at the same time such vectors for M₁(z), we prove completeness and even basis properties for the root vectors (including those for the resonances).     

Analysis of Operator Models Arising in Problems of Hereditary Mechanics

The correct solvability of initial-value problems for integrodifferential equations with unbounded operator coefficients in Hilbert spaces is determined. Numerous problems of hereditary mechanics and thermal physics have motivated the study of such equations. Models taking into account a Kelvin–Voight friction are considered. A spectral analysis of the operator functions, which are the symbols of integro-differential equations considered in this paper, is made.     

计算流体力学中的谱方法

本文论及偏微分方程数值解中的谱方法的理论基础和数值实现．评述近年来有关谱方法的最主要的几个研究领域，着重讨论区域分解技术，不同数学模型的耦合以及不同离散方法的耦合问题，并介绍一些最新结果．     

New Analytical and Numerical Results For Fractional Bogoyavlensky-Konopelchenko Equation Arising in Fluid Dynamics

In this article,(2+1)-dimensional time fractional Bogoyavlensky-Konopelchenko(BK)equation is studied,which describes the interaction of wave propagating along the x axis and y axis.To acquire the exact solutions of BK equation we employed sub equation method that is predicated on Riccati equation,and for numerical solutions the residual power series method is implemented.Some graphical results that compares the numerical and analytical solutions are given for di erent values of.Also comparative table for the obtained solutions is presented.     

Spectral Analysis of a Weighted Shift Operator with Unbounded Operator Coefficients

We obtain theorems on the structure of the resolvent of a weighted shift operator with unbounded operator coefficients which acts in Banach spaces of two-sided sequences of vectors.     

Spectral Analysis of the Differential Operator in Wavelet Bases

We analyze the spectral properties of the differential operator in wavelet bases. The problem is studied on a periodic domain, with periodized wavelets. An algorithm for finding the eigenvalue function of the differential operator is presented, and general conditions that ensure a "nicely behaving" eigenvalue function are derived.     

Spectral Analysis of Operator Polynomials and Second-Order Differential Operators

Mathematical Notes - Studying spectral properties of operator polynomials is reduced to studying the corresponding spectral properties of operators defined by operator matrices. The results are...     

Numerical Solution Methods for a Nonlinear Operator Equation Arising in an Inverse Coefficient Problem

Differential Equations - We consider the inverse problem of determining two unknown coefficients in a linear system of partial differential equations using additional information about one of the...     

Duality of Spectral Curves Arising in Two-Matrix Models

We consider the two-matrix model with the measure given by the exponential of a sum of polynomials in two different variables. We derive a sequence of pairs of dual finite-size systems of ODEs for the corresponding biorthonormal polynomials. We prove an inverse theorem, which shows how to reconstruct such measures from pairs of semi-infinite finite-band matrices, which define the recursion relations and satisfy the string equation. In the limit N, we prove that the obtained dual systems have the same spectral curve.     

Anisotropic Operator Symbols Arising From Multivariate Jump Processes

It is shown that infinitesimal generators of certain multivariate pure jump Lévy copula processes give rise to a class of anisotropic symbols that extends the well-known classes of pseudo differential operators of H?rmander-type. In addition, we provide minimal regularity convergence analysis for a sparse tensor product finite element approximation to solutions of the corresponding stationary Kolmogorov equations . The computational complexity of the presented approximation scheme is essentially independent of the underlying state space dimension.      

On an Inverse Spectral Problem for a Convolution Integro-differential Operator

The operator of double differentiation perturbed by the composition of a Volterra convolution operator and the differentiation one on a finite interval with Dirichlet boundary conditions is considered. It is proved that the standard asymptotics is necessary and sufficient for an arbitrary sequence of complex numbers to be the spectrum of such an operator, which is determined uniquely. A constructive procedure for solving the inverse problem is given. Received: March 5, 2007.     

Spectral Analysis of Differential Operators with Involution and Operator Groups

We study the spectral properties of differential operators with involution of the following two types: operators with involution multiplying the potential and operators with involution multiplying the derivative. The similar operator method is used to obtain a refined asymptotics of the eigenvalues and eigenvectors of such operators. These asymptotics are used to derive asymptotic formulas for the operator groups generated by the operators in question. These operator groups can be used to describe mild solutions of the corresponding mixed problems.     

Spectral Decomposition of Symmetric Operator Matrices

The authors study symmetric operator matrices in the product of Hilbert spaces H = H₁×H₂, where the entries are not necessarily bounded operators. Under suitable assumptions the closure L_o exists and is a selfadjoint operator in H. With L_o, the closure of the transfer function is considered. Under the assumption that there exists a real number β < inf p(A) such that M(β)<< 0, it follows that β ε p(L_o). Applying a factorization result of A.I. Virozub and V.I. Matsaev [VM] to the holomorphic operator function M(λ, the_spectral subspaces of L_o corresponding to the intervals ] — ∞, β] and [β, ∞[ and the restrictions of L_o to these subspaces are characterized. Similar results are proved for operator matrices which are symmetric in a Krein space.     

板几何中具反射边界条件的迁移算子的谱分析

在Lp(1 p<∞)空间上研究了板几何中具反射边界条件下各向异性、连续能量、非均匀介质的迁移方程,证明了该迁移算子产生C0半群的Dyson-Phillips展开式的二阶余项在Lp(1相似文献