On Some Properties of Linear Mapping Induced by Linear Descriptor Differential Equation

In this paper we introduce linear mapping D from WnF\subset Ln into Lm\times Rm, induced by linear differential equation d/dt Fx(t)-C(t)x(t)=f(t),Fx(t_0)=f_0. We prove that D is closed dense defined mapping for any m\times n-matrix F. Also adjoint mapping D* is constructed and its domain WmF is described. Some kind of so-called “integration by parts” formula for vectors from WnF, WmF is suggested. We obtain a necessary and sufficient condition for existence of generalized solution of equation Dx=(f,f_0). Also we find a sufficient criterion for closureness of the R(D) in Lm\times Rm which is formulated in terms of transparent conditions for blocks of matrix C(t). Some examples are supplied to illustrate obtained results.