We examine static spherically symmetric polytropic spheres in Palatini f(R)
gravity and show that no regular solutions to the field equations exist for
physically relevant cases such as a monatomic isentropic gas or a degenerate
electron gas, thus casting doubt on the validity of Palatini f(R) gravity as an
alternative to General Relativity.Comment: Talk given by EB at the 30th Spanish Relativity Meeting, 10 - 14
September 2007, Tenerife (Spain). Based on arXiv:gr-qc/0703132 and
arXiv:0712.1141 [gr-qc