Professor Avinash Khare

Molecular clouds (MC) are large aggregates of Hydrogen gas and dust ranging in size from 0.01 to 50 pc. The dust in these aggregates typically is silicates and/or PAH, dispersed inhomogeneously within the cloud. Due to a number of factors, the dust grains in the MC could acquire a finite charge. Thus the dust grains interact via Gravito-Yukawa (GY) potential; the gravitational interaction due to the mass and the screened Coulomb or Yukawa potential due to the finite dust charge in the ionized gas. In this talk, we study the dynamics of particles which interact via the GY potential. Our results show that an ensemble of such particles exists in two states. At high temperature Td , the dust is dispersed in a low density diffused state in the MC while for temperatures less than a critical value Tdc , the dust collapses in a small dense core within MC. Within the dust core there is a strong electric field which leads to an accumulation of ionised Hydrogen gas within the dust core. The critical temperature Tdc is found to be proportional to ndcore the dust density in the dense core. This result is obtained in three different ways; using mean field arguments (consistent with the thermodynamic limit) based on Helmholtz energy, law of corresponding states which show that the collapse to dense core to be a first order phase transition and using the Virial theorem which shows the transition to dense core to be a pitchfork bifurcation. The predictions of the theory e.g., Tdc a ndcore , collapse to dense core for Td < Tdc , latent heat of transition, existence of critical point, stability and oscillations of the dense core and the existence of electric field in the core etc. are verified in MD simulations. These results suggest that collapse of dust to dense core as the possible mechanism of formation of gas cores observed in molecular clouds.