Equilibration and freeze-out of an expanding gas in a transport approach in a Friedmann–Robertson–Walker metric

J. Tindall, J. M. Torres-Rincon, J. B. Rose, Ole H Petersen

Research output: Contribution to journalArticlepeer-review

12 Citations (SciVal)


Motivated by a recent finding of an exact solution of the relativistic Boltzmann equation in a Friedmann–Robertson–Walker spacetime, we implement this metric into the newly developed transport approach Simulating Many Accelerated Strongly-interacting Hadrons (SMASH). We study the numerical solution of the transport equation and compare it to this exact solution for massless particles. We also compare a different initial condition, for which the transport equation can be independently solved numerically. Very nice agreement is observed in both cases. Having passed these checks for the SMASH code, we study a gas of massive particles within the same spacetime, where the particle decoupling is forced by the Hubble expansion. In this simple scenario we present an analysis of the freeze-out times, as function of the masses and cross sections of the particles. The results might be of interest for their potential application to relativistic heavy-ion collisions, for the characterization of the freeze-out process in terms of hadron properties.

Original languageEnglish
Pages (from-to)532-538
Number of pages7
JournalPhysics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics
Early online date10 May 2017
Publication statusPublished - 10 Jul 2017


  • Boltzmann equation
  • Freeze-out
  • FRW spacetime
  • Transport model for heavy-ion collisions

ASJC Scopus subject areas

  • Nuclear and High Energy Physics


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