Convex Analysis and Duality

关于一致凸性周围的进一步定量模

Further quantitative moduli around uniform convexity

研究一致凸空间相关量，通过推导新公式，在线性与非线性方面取得进展。

Banach格之间线性算子的Y-凸性与$Y^{\times}$-凹性的对偶性

Duality between Y-convexity and $Y^{\times}$-concavity of linear operators between Banach lattices

本文研究了线性算子的Y-凸性，通过引入向量序列空间并利用相关算子的连续性对其进行刻画，同时得出了Y-凹性的类似结果，并最终证明了Y-凸性与$Y^{\times}$-凹性之间的对偶性。

Some convexity properties in direct integrals and Köthe-Bochner spaces

The notion of direct integrals introduced by Haydon, Levy and Raynaud in 1991 is a generalisation of the well-known concept of Köthe-Bochner spaces of vector-valued functions (using a family of target spaces instead of just one space). Here we will discuss some classical geometric properties like strict convexity, local uniform convexity and uniform convexity in direct integrals. We will also consider strongly convex and very convex Köthe-Bochner spaces.

A convexity of functions on convex metric spaces of Takahashi and applications

We quickly review and make some comments on the concept of convexity in metric spaces due to Takahashi. Then we introduce a concept of convex structure based convexity to functions on these spaces and refer to it as $W-$convexity. $W-$convex functions generalize convex functions on linear spaces. We discuss illustrative examples of (strict) $ W-$convex functions and dedicate the major part of this paper to proving a variety of properties that make them fit in very well with the classical theory of convex analysis. Finally, we apply some of our results to the metric projection problem and fixed…

Inequalities via φ_{h,m}-convexity

In this paper, we define φ_{h,m}-convex functions and prove some inequalities for this class.

Support, Convexity Conditions and Convex Hypersurfaces in Infinite Dimension

Working in infinite dimensional linear spaces, we deal with support for closed sets without interior. We generalize the Convexity Theorem for closed sets without interior. Finally we study the infinite dimensional version of Jordan hypersurfaces. Our whole work never assumes smoothness and is based exclusively on non-differential Convex Analysis tools and, in particular, on theory of convex cones. A crucial mathematical tool for our results is obtained solving the decomposition problem for non-closed non pointed cones.

On some inequalities for different kinds of convexity

In this paper, we obtained some inequalities for ϕ_{s}-convex function, ϕ-Godunova-Levin function, ϕ-P-function and log-ϕ-convex function. Finally, we defined the class of ϕ-quasi-convex functions and we examined some properties of this class.

Extending the Choquet theory: Trace convexity

We introduce the notion of trace convexity for functions and respectively, for subsets of a compact topological space. This notion generalizes both classical convexity of vector spaces, as well as Choquet convexity for compact metric spaces. We provide new notions of trace-convexification for sets and functions as well as a general version of Krein-Milman theorem. We show that the class of upper semicontinuous convex-trace functions attaining their maximum at exactly one Choquet-boundary point is residual and we obtain several enhanced versions of the maximum principle which generalize both th…

Uniformly convex subsets of the Hilbert space with modulus of convexity of the second order

We prove that in the Hilbert space every uniformly convex set with modulus of convexity of the second order at zero is an intersection of closed balls of fixed radius. We also obtain an estimate of this radius.

Convexity of quasi-entropy type functions: Lieb's and Ando's convexity theorems revisited

Given a positive function $f$ on $(0,\infty)$ and a non-zero real parameter $θ$, we consider a function $I_f^θ(A,B,X)=Tr X^*(f(L_AR_B^{-1})R_B)^θ(X)$ in three matrices $A,B>0$ and $X$. In the literature $θ=\pm1$ has been typical. The concept unifies various quantum information quantities such as quasi-entropy, monotone metrics, etc. We characterize joint convexity/concavity and monotonicity properties of the function $I_f^θ$, thus unifying some known results for various quantum quantities.

Convexity or concavity inequalities for Hermitian operators

Matrix versions of some basic convexity inequalities are given. Further results on the same topic are proved in the recent papers on arxiv: 1. Hermitian operators and convex functions, 2. A concavity inequality for symmetric norms, 3. Eigenvalue inequalities for convex and log-convex functions (with Jaspal Singh AUJLA).

Uniform convexity and the splitting problem for selections

We continue to investigate cases when the Repovš-Semenov splitting problem for selections has an affirmative solution for continuous set-valued mappings. We consider the situation in infinite-dimensional uniformly convex Banach spaces. We use the notion of Polyak of uniform convexity and modulus of uniform convexity for arbitrary convex sets (not necessary balls). We study general geometric properties of uniformly convex sets. We also obtain an affirmative solution of the splitting problem for selections of certain set-valued mappings with uniformly convex images.

Fixed points and selections of multifunctions on spaces with convexity

We provide theorems containnig both Kakutani and Browder fixed points theorems as immediate corollaries, as well as Michael and Browder selection theorems. For this purpose we introduce convex structures more general than those of locally convex and non-locally convex topological vector spaces or generalized convexity structures due to Michael, Van de Vel and Horvath.

How type of Convexity of the Core function affects the Csiszár $f$-divergence functional

We investigate how the type of Convexity of the Core function affects the Csiszár $f$-divergence functional. A general treatment for the type of convexity has been considered and the associated perspective functions have been studied. In particular, it has been shown that when the core function is \rm{MN}-convex, then the associated perspective function is jointly \rm{MN}-convex if the two scalar mean \rm{M} and \rm{N} are the same. In the case where $\mathrm{M}\neq\mathrm{N}$, we study the type of convexity of the perspective function. As an application, we prove that the \textit{Hellinger di…

Representation, relaxation and convexity for variational problems in Wiener spaces

We show convexity of solutions to a class of convex variational problems in the Gauss and in the Wiener space. An important tool in the proof is a representation formula for integral functionals in this infinite dimensional setting, that extends analogous results valid in the classical Euclidean framework.