Groups of Isometries of Hardy-Type Spaces of Analytic Functionals in the Unit Ball of the Space~L p

The tensor structure of spaces L _p (R ⁿ ) of summable functions of several variables is described. A scale of Hardy-type spaces of analytic functionals defined in the unit ball of the space L _p (R ¹) of summable functions of one variable is introduced. One-parameter groups of isometries of such spaces of analytic functionals are investigated.     

Tractability of approximating multivariate linear functionals

We review selected tractability results for approximating linear tensor product functionals defined over reproducing kernel Hilbert spaces. This review is based on Volume II of our book Tractability of Multivariate Problems. In particular, we show that all nontrivial linear tensor product functionals defined over a standard tensor product unweighted Sobolev space suffer the curse of dimensionality and therefore they are intractable. To vanquish the curse of dimensionality we need to consider weighted spaces, in which all groups of variables are monitored by weights. We restrict ourselves to product weights and provide necessary and sufficient conditions on these weights to obtain various kinds of tractability.     

Localization properties of highly singular generalized functions

We study the localization properties of generalized functions defined on a broad class of spaces of entire analytic test functions. This class, which includes all Gelfand-Shilov spaces S _α ^β (R ^k ) with β < 1, provides a convenient language for describing quantum fields with a highly singular infrared behavior. We show that the carrier cone notion, which replaces the support notion, can be correctly defined for the considered analytic functionals. In particular, we prove that each functional has a uniquely determined minimal carrier cone. __________ Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 151, No. 2, pp. 179–194, May, 2007.     

On the accuracy of cubature formulas in Sobolev spaces

We establish the necessary and sufficient conditions for the boundedness of the cubature formulas error functionals in spaces of type L _p ^m corresponding to the considered sets of integrable functions defined on bounded subsets of cylindrical and conical surfaces.     

Necessity of a Wiener type condition for boundary regularity of quasiminimizers and nonlinear elliptic equations

We use variational methods to obtain a pointwise estimate near a boundary point for quasisubminimizers of the p-energy integral and other integral functionals in doubling metric measure spaces admitting a p-Poincaré inequality. It implies a Wiener type condition necessary for boundary regularity for p-harmonic functions on metric spaces, as well as for (quasi)minimizers of various integral functionals and solutions of nonlinear elliptic equations on R ⁿ .     

On the power of standard information for <Emphasis Type="Italic">L</Emphasis><Subscript>∞</Subscript> approximation in the randomized setting

We study approximation of multivariate functions from a general separable reproducing kernel Hilbert space in the randomized setting with the error measured in the L _∞ norm. We consider algorithms that use standard information consisting of function values or general linear information consisting of arbitrary linear functionals. The power of standard or linear information is defined as, roughly speaking, the optimal rate of convergence of algorithms using n function values or linear functionals. We prove under certain assumptions that the power of standard information in the randomized setting is at least equal to the power of linear information in the worst case setting, and that the powers of linear and standard information in the randomized setting differ at most by 1/2. These assumptions are satisfied for spaces with weighted Korobov and Wiener reproducing kernels. For the Wiener case, the parameters in these assumptions are prohibitively large, and therefore we also present less restrictive assumptions and obtain other bounds on the power of standard information. Finally, we study tractability, which means that we want to guarantee that the errors depend at most polynomially on the number of variables and tend to zero polynomially in n ⁻¹ when n function values are used.     

Second-Order Epi-Derivatives of Composite Functionals

We compute two-sided second-order epi-derivatives for certain composite functionals f=gF where F is a C ¹ mapping between two Banach spaces X and Y, and g is a convex extended real-valued function on Y. These functionals include most essential objectives associated with smooth constrained minimization problems on Banach spaces. Our proof relies on our development of a formula for the second-order upper epi-derivative that mirrors a formula for a second-order lower epi-derivative from [7], and the two-sided results we obtain promise to support a more precise sensitivity analysis of parameterized optimization problems than has been previously possible.     

A fluctuations limit for scaled age distributions and weighted Sobolev spaces

It is shown that under the central-limit scaling, the fluctuations of the space—time renormalized age distributions of particles (whose development is controlled by critical linear birth and death processes) around the law-of-large-numbers limit converge in a Hilbert space (containing the class of signed Radon measures with finite moment generating functionals) to a continuous Gaussian process satisfying a Langevin equation. So far, the space of rapidly decreasing functions has been considered to be the natural state space for the kind of limit theorem considered here. However, the space of rapidly decreasing functions is not suitable in the present context and we are led to define an appropriate family of Sobolev spaces. In fact, we construct a scale of Hilbert spaces based on the eigenfunctions expansions of an elliptic operator defined on a weightedL ²-space.This research was partially supported by an NSERC of Canada grant.     

Critical point theorems and applications to a semilinear elliptic problem

The objective of this article is to establish the existence of critical points for functionals of classC ²defined on real Hilbert spaces. The argument is based on the infinite dimensional Morse theory introduced by Gromoll-Meyer [13]. The abstract results are applied to study the existence of nonzero solutions for a class of semilinear elliptic problems where the nonlinearity possesses a superlinear growth on a direction of the real line.This research was partially supported by CNPq/Brazil     

Repulsive knot energies and pseudodifferential calculus for O’Hara’s knot energy family E(α), α ∈ [2, 3)

We develop a precise analysis of J. O’Hara’s knot functionals E^(α), α ∈ [2, 3), that serve as self‐repulsive potentials on (knotted) closed curves. First we derive continuity of E^(α) on injective and regular H² curves and then we establish Fréchet differentiability of E^(α) and state several first variation formulae. Motivated by ideas of Z.‐X. He in his work on the specific functional E⁽²⁾, the so‐called Möbius Energy, we prove C^∞‐smoothness of critical points of the appropriately rescaled functionals $\tilde{E}^{(\alpha )}= {\rm length}^{\alpha -2}E^{(\alpha )}$ by means of fractional Sobolev spaces on a periodic interval and bilinear Fourier multipliers.     

Double <Emphasis Type="Italic">SO</Emphasis>(2, 1)-integrals and formulas for Whittaker functions

With the help of some double integral bilinear functionals with homogeneous kernels defined on a pair of representation spaces of the group SO(2, 1) we obtain some functional relations for Whittaker functions and calculate the sum of one series of Gauss hypergeometric functions converging to a Whittaker function.     

Methoden zur Bestimmung von Reprokernen

Methods to determine reproducing kernels. The explicit representation of continuous linear functionals on a Hilbert space by reprokernels is significant for interpolation and approximation. Starting with the kernels theorem, due to Schwartz, we develop methods to determine reprokernels for the Sobolev spaces W₂^k(Ω) if Ω R¹, and for some subspaces of W₂^k(Ω) if ΩRⁿ. Then we determine reprokernels for tensor products of Hilbert spaces. In addition to this we consider three types of limits of reprokernels.     

Evaluation Formulas for Conditional Function Space Integrals I

Abstract

In this article, we establish several explicit conditional function space integration formulas for functionals defined on a very general function space C _a,b [0,T]. The formulas we obtain are rather simple and don't involve function space integrals. In particular we obtain a formula for the conditional function space integral of each of the functionals exp{∫₀ ^T x(t)db(t)}, exp{?[∫₀ ^T x(t) db(t)]²}, and exp{? ∫₀ ^T x² (t) db(t)} which arise naturally in quantum mechanics.     

On the noncommutative residue and the heat trace expansion on conic manifolds

 Given a cone pseudodifferential operator P we give a full asymptotic expansion as t → 0 ⁺ of the trace Tr Pe ^-tA , where A is an elliptic cone differential operator for which the resolvent exists on a suitable region of the complex plane. Our expansion contains log t and new (log t)² terms whose coefficients are given explicitly by means of residue traces. Cone operators are contained in some natural algebras of pseudodifferential operators on which unique trace functionals can be defined. As a consequence of our explicit heat trace expansion, we recover all these trace functionals. Received: 12 November 2001 / Revised version: 26 June 2002 Mathematics Subject Classification (2000): Primary 58J35; Secondary 35C20, 58J42     

A counterexample to the Bishop-Phelps Theorem in complex spaces

The Bishop-Phelps Theorem asserts that the set of functionals which attain the maximum value on a closed bounded convex subsetS of a real Banach spaceX is norm dense inX ^*. We show that this statement cannot be extended to general complex Banach spaces by constructing a closed bounded convex set with no support points.     

Lipschitzian Properties of Integral Functionals on Lebesgue Spaces Lp, 1 \leqslant p < ￥\bf{L_p, 1 \leqslant {p} < \infty}

We give complete characterizations of integral functionals which are Lipschitzian on a Lebesgue space L _p with p ≠ ∞. When the measure is atomless, we characterize the integral functionals which are locally Lipschitzian on such Lebesgue spaces. In every cases, the Lipchitzian properties of the integral functional can be described by growth conditions on the subdifferentials of the integrand which are equivalent to Lipschitzian properties of the integrand.      

A remark on <Emphasis Type="Italic">L</Emphasis><Superscript><Emphasis Type="Italic">2,λ</Emphasis></Superscript> regularity for minimizers of quasilinear functionals

In this paper, we show the regularity in Morrey spaces L^2, for the gradient of minimizers of quasilinear functionals of the type We allow VMO dependence on the variable x and continuous dependence on the variable u.     

Spaces of Riemannian metrics

In this paper, we consider spaces M of Riemannian metrics on a closed manifold M. In the case where the manifold M is equipped with a symplectic or contact structure, we consider spaces AM of associated metrics. We study geometric and topological properties of these spaces and Riemannian functionals on spaces of metrics. __________ Translated from Sovremennaya Matematika i Ee Prilozheniya (Contemporary Mathematics and Its Applications), Vol. 31, Geometry, 2005.     

Riemannian convexity of functionals

This paper extends the Riemannian convexity concept to action functionals defined by multiple integrals associated to Lagrangian differential forms on first order jet bundles. The main results of this paper are based on the geodesic deformations theory and their impact on functionals in Riemannian setting. They include the basic properties of Riemannian convex functionals, the Riemannian convexity of functionals associated to differential m-forms or to Lagrangians of class C ¹ respectively C ², the generalization to invexity and geometric meaningful convex functionals. Riemannian convexity of functionals is the central ingredient for global optimization. We illustrate the novel features of this theory, as well as its versatility, by introducing new definitions, theorems and algorithms that bear upon the currently active subject of functionals in variational calculus and optimal control. In fact so deep rooted is the convexity notion that nonconvex problems are tackled by devising appropriate convex approximations.