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A stability result on Muckenhoupt's weights.

Juha Kinnunen — 1998

Publicacions Matemàtiques

We prove that Muckenhoupt's A-weights satisfy a reverse Hölder inequality with an explicit and asymptotically sharp estimate for the exponent. As a by-product we get a new characterization of A-weights.

Resistance Conditions and Applications

Juha KinnunenPilar Silvestre — 2013

Analysis and Geometry in Metric Spaces

This paper studies analytic aspects of so-called resistance conditions on metric measure spaces with a doubling measure. These conditions are weaker than the usually assumed Poincaré inequality, but however, they are sufficiently strong to imply several useful results in analysis on metric measure spaces. We show that under a perimeter resistance condition, the capacity of order one and the Hausdorff content of codimension one are comparable. Moreover, we have connections to the Sobolev inequality...

Summability of semicontinuous supersolutions to a quasilinear parabolic equation

Juha KinnunenPeter Lindqvist — 2005

Annali della Scuola Normale Superiore di Pisa - Classe di Scienze

We study the so-called p -superparabolic functions, which are defined as lower semicontinuous supersolutions of a quasilinear parabolic equation. In the linear case, when p = 2 , we have supercaloric functions and the heat equation. We show that the p -superparabolic functions have a spatial Sobolev gradient and a sharp summability exponent is given.

Hölder quasicontinuity of Sobolev functions on metric spaces.

Piotr HajlaszJuha Kinnunen — 1998

Revista Matemática Iberoamericana

We prove that every Sobolev function defined on a metric space coincides with a Hölder continuous function outside a set of small Hausdorff content or capacity. Moreover, the Hölder continuous function can be chosen so that it approximates the given function in the Sobolev norm. This is a generalization of a result of Malý [Ma1] to the Sobolev spaces on metric spaces [H1].

Lebesgue points for Sobolev functions on metric spaces.

Juha KinnunenVisa Latvala — 2002

Revista Matemática Iberoamericana

Our main objective is to study the pointwise behaviour of Sobolev functions on a metric measure space. We prove that a Sobolev function has Lebesgue points outside a set of capacity zero if the measure is doubling. This result seems to be new even for the weighted Sobolev spaces on Euclidean spaces. The crucial ingredient of our argument is a maximal function related to discrete convolution approximations. In particular, we do not use the Besicovitch covering theorem, extension theorems or representation...

Relaxation and Integral Representation for Functionals of Linear Growth on Metric Measure spaces

Heikki HakkarainenJuha KinnunenPanu LahtiPekka Lehtelä — 2016

Analysis and Geometry in Metric Spaces

This article studies an integral representation of functionals of linear growth on metric measure spaces with a doubling measure and a Poincaré inequality. Such a functional is defined via relaxation, and it defines a Radon measure on the space. For the singular part of the functional, we get the expected integral representation with respect to the variation measure. A new feature is that in the representation for the absolutely continuous part, a constant appears already in the weighted Euclidean...

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