Optical mode crossings and the low temperature anomalies of SrTiO3
  Optical mode crossing is not a plausible explanation for the new broad Brillouin doublet nor for the strong acoustic anomalies observed at low temperatures in SrTiO3. Data presented to support that explanation are also inconclusive. 
E. Courtens, B. Hehlen, E. Farhi, and A.K. Tagantsev