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

Abstract

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.

v2: 9 pages, 7 figures. Added discussion on the numerical relation between the Hubble and scattering rates at the end of Sec. 3. Updated references. This version matches the accepted manuscript by Phys.Lett.B journal

References in corpus (4)

• A new exact solution of the relativistic Boltzmann equation and its hydrodynamic limit
• Nonlinear dynamics from the relativistic Boltzmann equation in the Friedmann-Lemaître-Robertson-Walker spacetime
• Analytic solutions of the relativistic Boltzmann equation
• $p_t$-Angular power spectrum in ALICE events

Cited by in corpus (11)

• Particle Production via Strings and Baryon Stopping within a Hadronic Transport Approach
• SMASH -- A new hadronic transport approach
• Jet quenching in the hadron gas: an exploratory study
• Benchmarking a Non-Equilibrium Approach to Photon Emission in Relativistic Heavy-Ion Collisions
• Strangeness production via resonances in heavy-ion collisions at SIS energies
• Study of transport coefficients in ultrarelativistic kinetic theory
• Modeling the Past Hypothesis: A Mechanical Cosmology
• Maximally Symmetric Boost-Invariant Solutions of the Boltzmann Equation in Foliated Geometries
• Transport Model Comparison Studies of Intermediate-Energy Heavy-Ion Collisions
• Calculation of Power Spectrum in the Little Bangs
• Melting and freeze-out conditions of hadrons in a thermal medium