Physics of Non-Universal Larson's Relation
  From a new perspective, we re-examine self-gravity and turbulence jointly, in
hopes of understanding the physical basis for one of the most important
empirical relations governing clouds in the interstellar medium (ISM), the
Larson's Relation relating velocity dispersion ($\sigma_R$) to cloud size
($R$). We report on two key new findings. First, the correct form of the
Larson's Relation is $\sigma_R=\alpha_v^{1/5}\sigma_{pc}(R/1pc)^{3/5}$, where
$\alpha_v$ is the virial parameter of clouds and $\sigma_{pc}$ is the strength
of the turbulence, if the turbulence has the Kolmogorov spectrum. Second, the
amplitude of the Larson's Relation, $\sigma_{pc}$, is not universal, differing
by a factor of about two between clouds on the Galactic disk and those at the
Galactic center, evidenced by observational data.
