Weakly Differentiable Functions: Sobolev Spaces and Functions of Bounded Variation (Paperback, Softcover Repri)

'1 Preliminaries.- 1.1 Notation.- Inner product of vectors.- Support of a function.- Boundary of a set.- Distance from a point to a set.- Characteristic function of a set.- Multi-indices.- Partial derivative operators.- Function spaces-continuous, Holder continuous, Holder continuous derivatives.- 1.2 Measures on Rn.- Lebesgue measurable sets.- Lebesgue measurability of Borel sets.- Suslin sets.- 1.3 Covering Theorems.- Hausdorff maximal principle.- General covering theorem.- Vitali covering theorem.- Covering lemma, with n-balls whose radii vary in Lipschitzian way.- Besicovitch covering lemma.- Besicovitch differentiation theorem.- 1.4 Hausdorff Measure.- Equivalence of Hausdorff and Lebesgue measures.- Hausdorff dimension.- 1.5 Lp-Spaces.- Integration of a function via its distribution function.- Young's inequality.- Holder's and Jensen's inequality.- 1.6 Regularization.- Lp-spaces and regularization.- 1.7 Distributions.- Functions and measures, as distributions.- Positive distributions.- Distributions determined by their local behavior.- Convolution of distributions.- Differentiation of distributions.- 1.8 Lorentz Spaces.- Non-increasing rearrangement of a function.- Elementary properties of rearranged functions.- Lorentz spaces.- O'Neil's inequality, for rearranged functions.- Equivalence of Lp-norm and (p, p)-norm.- Hardy's inequality.- Inclusion relations of Lorentz spaces.- Exercises.- Historical Notes.- 2 Sobolev Spaces and Their Basic Properties.- 2.1 Weak Derivatives.- Sobolev spaces.- Absolute continuity on lines.- Lp-norm of difference quotients.- Truncation of Sobolev functions.- Composition of Sobolev functions.- 2.2 Change of Variables for Sobolev Functions.- Rademacher's theorem.- Bi-Lipschitzian change of variables.- 2.3 Approximation of Sobolev Functions by Smooth Functions.- Partition of unity.- Smooth functions are dense in Wk,p.- 2.4 Sobolev Inequalities.- Sobolev's inequality.- 2.5 The Rellich-Kondrachov Compactness Theorem.- Extension domains.- 2.6 Bessel Potentials and Capacity.- Riesz and Bessel kernels.- Bessel potentials.- Bessel capacity.- Basic properties of Bessel capacity.- Capacitability of Suslin sets.- Minimax theorem and alternate formulation of Bessel capacity.- Metric properties of Bessel capacity.- 2.7 The Best Constant in the Sobolev Inequality.- Co-area formula.- Sobolev's inequality and isoperimetric inequality.- 2.8 Alternate Proofs of the Fundamental Inequalities.- Hardy-Littlewood-Wiener maximal theorem.- Sobolev's inequality for Riesz potentials.- 2.9 Limiting Cases of the Sobolev Inequality.- The case kp=n by infinite series.- The best constant in the case kp = n.- An L?-bound in the limiting case.- 2.10 Lorentz Spaces, A Slight Improvement.- Young's inequality in the context of Lorentz spaces.- Sobolev's inequality in Lorentz spaces.- The limiting case.- Exercises.- Historical Notes.- 3 Pointwise Behavior of Sobolev Functions.- 3.1 Limits of Integral Averages of Sobolev Functions.- Limiting values of integral averages except for capacity null set.- 3.2 Densities of Measures.- 3.3 Lebesgue Points for Sobolev Functions.- Existence of Lebesgue points except for capacity null set.- Approximate continuity.- Fine continuity everywhere except for capacity null set.- 3.4 LP-Derivatives for Sobolev Functions.- Existence of Taylor expansions Lp.- 3.5 Properties of Lp-Derivatives.- The Spaces TktkTk,ptk,p.- The implication of a function being in Tk,pat all points of a closed set.- 3.6 An Lp-Version of the Whitney Extension Theorem.- Existence of a C? function comparable to the.- distance function to a closed set.- The Whitney extension theorem for functions in Tk,p and tk,p.- 3.7 An Observation on Differentiation.- 3.8 Rademacher's Theorem in the Lp-Context.- A function in Tk,peverywhere implies it is in tk,palmost everywhere.- 3.9 The Implications of Pointwise Differentiability.- Comparison o