Boundaries of Asplund spaces

We study the relationship between the classical combinatorial inequalities of Simons and the more recent (I)-property of Fonf and Lindenstrauss. We obtain a characterization of strong boundaries for Asplund spaces using the new concept of finitely self-predictable set. Strong properties for w^∗-K-analytic boundaries are established as well as a sup-lim sup theorem for Baire maps.     

The Dunkl-Williams constant, convexity, smoothness and normal structure

In this paper we exhibit some connections between the Dunkl-Williams constant and some other well-known constants and notions. We establish bounds for the Dunkl-Williams constant that explain and quantify a characterization of uniformly nonsquare Banach spaces in terms of the Dunkl-Williams constant given by M. Baronti and P.L. Papini. We also study the relationship between Dunkl-Williams constant, the fixed point property for nonexpansive mappings and normal structure.     

Renorming James tree space

We show that the James tree space can be renormed to be Lipschitz separated. This negatively answers the question of J. Borwein, J. Giles and J. Vanderwerff as to whether every Lipschitz separated Banach space is an Asplund space.

     

Maximal Monotone Multifunctions of Br?ndsted–Rockafellar Type

We consider whether the inequality-splitting property established in the Brøndsted–Rockafellar theorem for the subdifferential of a proper convex lower semicontinuous function on a Banach space has an analog for arbitrary maximal monotone multifunctions. We introduce the maximal monotone multifunctions of type (ED), for which an inequality-splitting property does hold. These multifunctions form a subclass of Gossez"s maximal monotone multifunctions of type (D); however, in every case where it has been proved that a multifunction is maximal monotone of type (D) then it is also of type (ED). Specifically, the following maximal monotone multifunctions are of type (ED): ultramaximal monotone multifunctions, which occur in the study of certain nonlinear elliptic functional equations; single-valued linear operators that are maximal monotone of type (D); subdifferentials of proper convex lower semicontinuous functions; subdifferentials of certain saddle-functions. We discuss the negative alignment set of a maximal monotone multifunction of type (ED) with respect to a point not in its graph – a mysterious continuous curve without end-points lying in the interior of the first quadrant of the plane. We deduce new inequality-splitting properties of subdifferentials, almost giving a substantial generalization of the original Brøndsted–Rockafellar theorem. We develop some mathematical infrastructure, some specific to multifunctions, some with possible applications to other areas of nonlinear analysis: the formula for the biconjugate of the pointwise maximum of a finite set of convex functions – in a situation where the obvious formula for the conjugate fails; a new topology on the bidual of a Banach space – in some respects, quite well behaved, but in other respects, quite pathological; an existence theorem for bounded linear functionals – unusual in that it does not assume the existence of any a priori bound; the 'big convexification" of a multifunction.