A hybrid variational principle for the Keller–Segel system in ℝ2 Adrien Blanchet, José Antonio Carrillo, David Kinderlehrer, Michał Kowalczyk, Philippe Laurençot and Stefano Lisini ESAIM: M2AN, 49 6 (2015) 1553-1576 Published online: 05 November 2015 DOI: 10.1051/m2an/2015021