Analogue cosmology in a hadronic fluid

The expansion of hadronic matter that takes place immediately after a heavy ion collision has certain similarity with the cosmological expansion. We study the analogue geometry of the expanding hadronic fluid, using the the formalism of relativistic acoustic geometry. We show that the propagation of massless pions provides a geometric analog of expanding spacetime equivalent to an open (k=-1)FRW cosmology. Here, we study general conditions for the formation of a trapped region with the inner boundary as a marginally trapped surface.