We consider the class of planar maps with Jacobian prescribed to be a fixed radially symmetric function and which, moreover, fixes the boundary of a ball; we then study maps which minimise the 2-Dirichlet energy in this class. We find a quantity which controls the symmetry, uniqueness and regularity of minimisers: if then minimisers are symmetric and unique; if is large but finite then there may be uncountably many minimisers, none of which is symmetric, although all of them have optimal regularity; if is infinite then generically minimisers have lower regularity. In particular, this result gives a negative answer to a question of Hélein (Ann. Inst. H. Poincaré Anal. Non Linéaire 11(3):275-296, 1994). Some of our results also extend to the setting where the ball is replaced by and boundary conditions are not prescribed.
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http://dx.doi.org/10.1007/s00205-021-01699-4 | DOI Listing |
J Math Biol
October 2022
School of Mathematics and Statistics, University of Sheffield, Hicks Building, Hounsfield Road, Sheffield, S3 7RH, UK.
Deriving emergent patterns from models of biological processes is a core concern of mathematical biology. In the context of partial differential equations, these emergent patterns sometimes appear as local minimisers of a corresponding energy functional. Here we give methods for determining the qualitative structure of local minimum energy states of a broad class of multi-species nonlocal advection-diffusion models, recently proposed for modelling the spatial structure of ecosystems.
View Article and Find Full Text PDFArch Ration Mech Anal
October 2021
Department of Mathematics and Statistics, University of Helsinki, P.O. Box 68, 00014 Helsingin Yliopisto, Finland.
We consider the class of planar maps with Jacobian prescribed to be a fixed radially symmetric function and which, moreover, fixes the boundary of a ball; we then study maps which minimise the 2-Dirichlet energy in this class. We find a quantity which controls the symmetry, uniqueness and regularity of minimisers: if then minimisers are symmetric and unique; if is large but finite then there may be uncountably many minimisers, none of which is symmetric, although all of them have optimal regularity; if is infinite then generically minimisers have lower regularity. In particular, this result gives a negative answer to a question of Hélein (Ann.
View Article and Find Full Text PDFCalc Var Partial Differ Equ
August 2018
4Dipartimento di Ingegneria, Università degli Studi di Napoli "Parthenope", 80143 Naples, Italy.
We consider macroscopic descriptions of particles where repulsion is modelled by non-linear power-law diffusion and attraction by a homogeneous singular kernel leading to variants of the Keller-Segel model of chemotaxis. We analyse the regime in which diffusive forces are stronger than attraction between particles, known as the diffusion-dominated regime, and show that all stationary states of the system are radially symmetric non-increasing and compactly supported. The model can be formulated as a gradient flow of a free energy functional for which the overall convexity properties are not known.
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