The argument stems from the interferometry work published in Nature earlier this year:
Müller H, Peters A, & Chu S (2010). A precision measurement of the gravitational redshift by the interference of matter waves. Nature, 463 (7283), 926-9 PMID: 20164925
Cohen-Tannoudji says, “Wrong.”
Wolf P, Blanchet L, Bordé CJ, Reynaud S, Salomon C, & Cohen-Tannoudji C (2010). Atom gravimeters and gravitational redshift. Nature, 467 (7311) PMID: 20811407
Chu says, “I’m right.”
Müller H, Peters A, & Chu S (2010). Müller, Peters & Chu reply. Nature, 467 (7311) PMID: 20811408
And in the end, I still have no clue what’s going on. Would anyone more informed out there care to explain?