Dispersion Relations of Longitudinal and Transverse Waves in a Rarefied Polyatomic Gas based on Rational Extended Thermodynamics

We present a complete analysis of the dispersion relations for longitudinal and transverse waves in a rarefied polyatomic gas based on Rational Extended Thermodynamics (RET), which describes the evolution of a non-polytropic gas in nonequilibrium. Observability of the second mode of the longitudinal wave and the transverse wave is discussed although these waves are usually not payed much attention. The cases of CO${}_2$ gas and para-H${}_2$ gas are specifically analyzed as typical examples.