In this note we show that weak solutions to the wave map problem in the energy-supercritical dimension 3 are not unique. On the one hand, we find weak solutions using the penalization method introduced by Shatah [12] and show that they satisfy a local energy inequality. On the other hand we build on a special harmonic map to construct a weak solution to the wave map problem, which violates this energy inequality.Finally we establish a local weak-strong uniqueness argument in the spirit of Struwe [15] which we employ to show that one may even have a failure of uniqueness for a Cauchy problem with a stationary solution. We thus obtain a result analogous to the one of Coron [2] for the case of the heat flow of harmonic maps.
@article{AIHPC_2015__32_3_519_0, author = {Widmayer, Klaus}, title = {Non-uniqueness of weak solutions to the wave map problem}, journal = {Annales de l'I.H.P. Analyse non lin\'eaire}, volume = {32}, year = {2015}, pages = {519-532}, doi = {10.1016/j.anihpc.2014.02.001}, mrnumber = {3353699}, zbl = {1320.35006}, language = {en}, url = {http://dml.mathdoc.fr/item/AIHPC_2015__32_3_519_0} }
Widmayer, Klaus. Non-uniqueness of weak solutions to the wave map problem. Annales de l'I.H.P. Analyse non linéaire, Tome 32 (2015) pp. 519-532. doi : 10.1016/j.anihpc.2014.02.001. http://gdmltest.u-ga.fr/item/AIHPC_2015__32_3_519_0/
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