Why even source-free gravity must be quantized
S. Deser (Walter Burke Institute for Theoretical Physics, California Institute of Technology, Pasadena, CA, 91125, USA, Physics Department, Brandeis University, Waltham, MA, 02454, USA)
I note, on the most elementary grounds: its classical ultraviolet catastrophe, that even source-free General Relativity must be quantized, despite some eminent opinions to the contrary and with a little fine print.