A general vectorial Ekeland’s variational principle with a P-distance

In this paper, by using p-distances on uniform spaces, we establish a general vectorial Ekeland variational principle （in short EVP）, where the objective function is defined on a uniform space and taking values in a pre-ordered real linear space and the perturbation involves a p-distance and a monotone function of the objective function. Since p-distances are very extensive, such a form of the perturbation in deed contains many different forms of perturbations appeared in the previous versions of EVP. Besides, we only require the objective function has a very weak property, as a substitute for lower semi-continuity, and only require the domain space （which is a uniform space） has a very weak type of completeness, i.e., completeness with respect to a certain p-distance. Such very weak type of completeness even includes local completeness when the uniform space is a locally convex topological vector space. From the general vectorial EVP, we deduce a general vectorial Caristi＇s fixed point theorem and a general vectorial Takahashi＇s nonconvex minimization theorem. Moreover, we show that the above three theorems are equivalent to each other. We see that the above general vectorial EVP includes many particular versions of EVP, which extend and complement the related known results.     

On Ha＇s Version of Set-valued Ekeland＇s Variational Principle

By using the concept of cone extensions and Dancs-Hegedus-Medvegyev theorem, Ha [Some variants of the Ekeland variational principle for a set-valued map. J. Optim. Theory Appl., 124, 187–206 (2005)] established a new version of Ekeland’s variational principle for set-valued maps, which is expressed by the existence of strict approximate minimizer for a set-valued optimization problem. In this paper, we give an improvement of Ha’s version of set-valued Ekeland’s variational principle. Our proof is direct and it need not use Dancs-Hegedus-Medvegyev theorem. From the improved Ha’s version, we deduce a Caristi-Kirk’s fixed point theorem and a Takahashi’s nonconvex minimization theorem for set-valued maps. Moreover, we prove that the above three theorems are equivalent to each other.     

VECTORIAL EKELAND＇S VARIATIONAL PRINCIPLE WITH A W-DISTANCE AND ITS EQUIVALENT THEOREMS

By using the properties of w-distances and Gerstewitz’s functions,we first give a vectorial Takahashi’s nonconvex minimization theorem with a w-distance.From this,we deduce a general vectorial Ekeland’s variational principle,where the objective function is from a complete metric space into a pre-ordered topological vector space and the perturbation contains a w-distance and a non-decreasing function of the objective function value.From the general vectorial variational principle,we deduce a vectorial Caristi’s fixed point theorem with a w-distance.Finally we show that the above three theorems are equivalent to each other.The related known results are generalized and improved.In particular,some conditions in the theorems of [Y.Araya,Ekeland’s variational principle and its equivalent theorems in vector optimization,J.Math.Anal.Appl.346(2008),9-16] are weakened or even completely relieved.     

Projection pressure and Bowen’s equation for a class of self-similar fractals with overlap structure

Let {Si}il=1 be an iterated function system (IFS) on Rd with attractor K. Let π be the canonical projection. In this paper, we define a new concept called projection pressure Pπ(φ) for ∈ C(Rd) under certain affine IFS, and show the variational principle about the projection pressure. Furthermore, we check that the unique zero root of projection pressure still satisfies Bowen’s equation when each Si is the similar map with the same compression ratio. Using the root of Bowen’s equation, we can get the Hausdorff dimension of the attractor K.     

Auslander’s defect formula and a commutative triangle in an exact category

We prove Auslander’s defect formula in an exact category,and obtain a commutative triangle involving the Auslander bijections and the generalized Auslander Reiten duality.