The maximal Abelian dimension of linear algebras formed by strictly upper triangular matrices

We compute the largest dimension of the Abelian Lie subalgebras contained in the Lie algebra of n×n strictly upper triangular matrices, where n ∈ ℕ \ {1}. We do this by proving a conjecture, which we previously advanced, about this dimension. We introduce an algorithm and use it first to study the two simplest particular cases and then to study the general case. __________ Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 152, No. 3, pp. 419–429, September, 2007.     

具有多偏差变元的Rayleigh方程周期解的存在性

利用Mawhin连续性定理研究了具有多偏差变元的Rayleigh方程周期解的存在性,得到了一些新的结果,补充和完善了已有的结果.     

矩阵方程AXAT+BYBT=C的亚半正定解

讨论了矩阵方程AXAT+BYBT=C关于亚半正定矩阵X,Y有解的充要条件,并在有解时给出了解的通式.     

A One-Dimensional Inviscid and Compressible Fluid in a Harmonic Potential Well

A Hamiltonian model is analyzed for a one-dimensional inviscid compressible fluid. The space–time evolution of the fluid is governed by the following system of the Hamilton–Jacobi and the continuity equations:

On subnormal solutions of second order linear periodic differential equations

In this paper, we investigate the existence and the form of subnormal solution for a class of second order periodic linear differential equations, estimate the growth properties of all solutions, and answer the question raised by Gundersen and Steinbart.     

具有连续时滞的非自治扩散Lotka-volterra模型的渐近性

持续生存概念是种群生态系统稳定性的一个重要描述,而研究竞争种群共存的问题是种群生态学的一个重要问题,考虑非自治的两种群L otka-vo lterra周期系数的时滞扩散摸型,通过构造李亚普诺夫泛函,微分不等式等获得了其一致持续生存及正周期解存在与全局渐近稳定的充分条件.     

Incorporating model uncertainty into optimal insurance contract design

In stochastic optimization models, the optimal solution heavily depends on the selected probability model for the scenarios. However, the scenario models are typically chosen on the basis of statistical estimates and are therefore subject to model error. We demonstrate here how the model uncertainty can be incorporated into the decision making process. We use a nonparametric approach for quantifying the model uncertainty and a minimax setup to find model-robust solutions. The method is illustrated by a risk management problem involving the optimal design of an insurance contract.     

Evolutionary Boussinesq model with nonmonotone friction and heat flux boundary conditions

In this paper we prove the existence and regularity of a solution to a two-dimensional system of evolutionary hemivariational inequalities which describes the Boussinesq model with nonmonotone friction and heat flux. We use the time retardation and regularization technique, combined with a regularized Galerkin method, and recent results from the theory of hemivariational inequalities.     

Renormalized solutions of elliptic equations with Robin boundary conditions

In the present paper, we consider elliptic equations with nonlinear and nonhomogeneous Robin boundary conditions of the type{-div(B(x, u)▽u) = f in ?,u = 0 on Γ_0,B(x, u)▽u·n→+γ(x)h(u) =g on Γ_1,where f and g are the element of L~1(?) and L~1(Γ_1), respectively. We define a notion of renormalized solution and we prove the existence of a solution. Under additional assumptions on the matrix field B we show that the renormalized solution is unique.