“…where in each case m − n needs to be odd in order for the coefficient to be nonvanishing. The particle creation resonance ( 7) is well known in the DCE literature [3,4,28,29,30,31,32,33,34,35,36,37,38]. The mode mixing resonance ( 6) is also known [29,30,31,32,33,34,35] but seems to have received significant attention only in situations where it happens to coincide with a particle creation resonance.…”