  Analytical solutions to the microscopic Boltzmann equation are useful in
testing the applicability and accuracy of macroscopic hydrodynamic theory. In
this work, we present exact solutions of the relativistic Boltzmann equation,
based on a new family of exact solutions of the relativistic ideal hydrodynamic
equations [Phys. Rev. C 105, L021902].. To the best of our knowledge, this is
the first exact solution that allows longitudinal expansion with broken boost
invariance.
