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math.FA2026
Preserving Besov (fractional Sobolev) energies under sphericalization and flattening
Anders Björn, Jana Björn, Riikka Korte +2
We introduce a new sphericalization mapping for metric spaces that is applicable in very general situations, including totally disconnected fractal type sets. For an unbounded comp…
math.FA2025
Doubling measures and Poincaré inequalities for sphericalizations of metric spaces, with applications to -harmonic functions in unbounded domains
Anders Björn, Anders Björn, Jana Björn +2
The identification between the complex plane and the Riemann sphere preserves holomorphic and harmonic functions and is a classical tool. In this paper we consider a similar mappin…
math.FA2025
Non-quasicontinuous Newtonian functions and outer capacities based on Banach function spaces
Anders Björn, Jana Björn, Lukáš Malý
We construct various examples of Sobolev-type functions, defined via upper gradients in metric spaces, that fail to be quasicontinuous or weakly quasicontinuous. This is done with…