MAXIMAL SUBSPACES FOR SOLUTIONS OF THE SECOND ORDER ABSTRACT CAUCHY PROBLEM

For a continuous, increasing function ω ： R^＋ →R^＋／{0} of finite exponential type, this paper introduces the set Z（A, ω） of all x in a Banach space X for which the second order abstract differential equation （2） has a mild solution such that [ω（t）]^-1u（t,x） is uniformly continues on R^＋, and show that Z（A, ω） is a maximal Banach subspace continuously embedded in X, where A ∈ B（X） is closed. Moreover, A[z（A,ω） generates an O（ω（t）） strongly continuous cosine operator function family.

C-Wellposedness of the Complete Second Order Abstract Cauchy Problem and Applications

In this paper,we first give a sufficient and necessary condition for M= to generate an exponentially bounded =-semigroup and discuss its relations to the C-wellposedness of the complete second order abstract Cauchy problem （（ACP2） for short） in some sense.Then we use these results and those in [1] to discuss the C-（exponential） wellposedness of a kind of （ACP2） with application backgrounds,and develop the results in [2].

THE ABSTRACT CAUCHY PROBLEM AND A GENERALIZATION OF THE LUMER-PHILLIPS THEOREM

For injective, bounded operator C on a Banach space X , the author defines the C -dissipative operator, and then gives Lumer-Phillips characterizations of the generators of quasi-contractive C -semigroups, where a C -semigroup T(·) is quasi-contractive if ‖T(t)x‖‖Cx‖ for all t0 and x∈X . This kind of generators guarantee that the associate abstract Cauchy problem u′(t,x)=Au(t,x) has a unique nonincreasing solution when the initial data is in C(D(A)) (here D(A) is the domain of A ). Also, the generators of quasi isometric C -semigroups are characterized.

ADDITIVE PERTURBATIONS OF LOCAL C-SEMIGROUPS

In this paper, we apply the contraction mapping theorem to establish some bounded and unbounded additive perturbation theorems concerning local C-semigroups. Some growth conditions of perturbations of local C-semigroups axe also established.

MULTIPLICATIVE PERTURBATIONS OF LOCAL α-TIMES INTEGRATED C-SEMIGROUPS

We establish some left and right multiplicative perturbations of a local α-timesintegrated C-semigroup S（·） on a complex Banach space X with non-densely defined genera- tor, which can be applied to obtain some additive perturbation results concerning S（·）. Some growth conditions of the perturbations of S（·） are also established.

GLOBAL EXISTENCE FOR SEMILINEAR RETARDED FUNCTIONAL DIFFERENTIAL EQUATIONS WITH INFINITE DELAY

This paper is concerned with the global existence of solutions for abstract retarded functional differential equations （RFDEs） with infinite delay, via a fixed point approach. Some sufficient conditions are established under which the existence of a globally mild solution are obtained by using Leray-Schauder.

Existence and Uniqueness of Endemic States for the Age-structured MSEIR Epidemic Model

The existence and uniqueness of positive steady states for the age-structured MSEIR epidemic model with age-dependent transmission coefficient is considered. Threshold results for the existence of endemic states are established; under certain conditions, uniqueness is also shown.