Lukewarm black holes in quadratic gravity
  Perturbative solutions to the fourth-order gravity describing spherically-symmetric, static and electrically charged black hole in an asymptotically de Sitter universe is constructed and discussed. Special emphasis is put on the lukewarm configurations, in which the temperature of the event horizon equals the temperature of the cosmological horizon. 
Jerzy Matyjasek and Katarzyna Zwierzchowska
gr-qc hep-th