Let C be a nonempty, closed, and convex subset of a real Hilbert space H . Denote the metric projection from x ∈ H onto C by PCx. Let T : C → C be a nonexpansive mapping on C, that is, T : C → C and ‖Tx − Ty‖ ≤ ‖x − y‖, for all x, y ∈ C. We use F T to denote the set of fixed points of T , that is, F T {x ∈ C : x Tx}. Let {T s : s > 0} be a nonexpansive semigroup on a closed convex subset C, tha...

In this paper we study the boundedness of extension operators associated with spheres in vector spaces over finite fields. In even dimensions, we estimate the number of incidences between spheres and points in the translated set from a subset of spheres. As a result, we improve the Tomas-Stein exponents, previous results by the authors in [6]. The analytic approach and the explicit formula for ...

Tube formulas (by which we mean an explicit formula for the volume of an (inner) ε-neighbourhood of a subset of a suitable metric space) have been used in many situations to study properties of the subset. For smooth submanifolds of Euclidean space, this includes Weyl’s celebrated results on spectral asymptotics, and the subsequent relation between curvature and spectrum. Additionally, a tube f...

The purpose of this paper is to establish the Lipschitz norm and BMO norm inequalities for the composition of the homotopy operator T and the projection operator H applied to differential forms in R, n ≥ 2. The harmonic projection operator H, one of the key operators in the harmonic analysis, plays an important role in the Hodge decomposition theory of differential forms. In the meanwhile, the ...

New affine invariant functionals for convex polytopes are introduced. Some sharp affine isoperimetric inequalities are established for the new functionals. These new inequalities lead to fairly strong volume estimates for projection bodies. Two of the new affine isoperimetric inequalities are extensions of Ball’s reverse isoperimetric inequalities. If K is a convex body (i.e., a compact, convex...

Proof. By composing Y with a homeomorphism R→ (0, 1) if required, we may assume that Y is bounded and we do so. To prove the claim, we appeal to the standard machinery using the monotone class theorem. Let L∞ be the family of bounded σ(X )-measurable functions and let H be the subset of L∞ defined by H = {Y ∈ L∞ : ∃ a Borel-measurable f satisfying Y = f (X ) a.s.}. We claim thatH = L∞. To this ...

Pure bargaining games discussed in the previous two lectures are a special case of n-person cooperative games. In the general setup coalitions other than the grand coalition matter as well. The primitive is the coalitional form (or, "coalitional function", or "characteristic form"). The primitive can represent many different things, e.g., a simple voting game where we associate to a winning coa...

Abstract. This paper presents a new observability estimate for parabolic equations in × (0, T ), where  is a convex domain. The observation region is restricted over a product set of an open nonempty subset of  and a subset of positive measure in (0, T ). This estimate is derived with the aid of a quantitative unique continuation at one point in time. Applications to the bang-bang property f...

In the multidimensional knapsack problem a set of items, each with a value and a multidimensional size, is given and we want to select a subset of them in such a way that the total value of the selected items is maximized while the total size satisfies some capacity constraint for each dimension. In this paper we assume that the sizes are independent random variables such that each size follows...

We study an analogue of Garkavi’s result on proximinal subspaces of C(X) of finite codimension in the context of the space A(K) of affine continuous functions on a compact convex set K. We give an example to show that a simple-minded analogue of Garkavi’s result fails for these spaces. When K is a metrizable Choquet simplex, we give a necessary and sufficient condition for a boundary measure to...