FiVoHydro.jl — a finite-volume solver for boost-invariant relativistic viscous hydrodynamics with a diffusing heavy-quark charge

FiVoHydro.jl (FiVo) solves boost-invariant relativistic viscous hydrodynamics in Milne coordinates together with a diffusing heavy-quark (charm) charge, in radial 1+1D and transverse 2+1D. The bulk solvers are conservative finite volume: HLLE with MUSCL reconstruction in primitive variables, SSPRK2/3 time stepping, operator-split relaxation of the dissipative fields, and a MOOD fallback. The charm second-moment solver, whose equations have no conservative form, is integrated in quasi-linear form with RK4. It ships a validation ladder in which every gate is judged by a referee that is not the code under test — a closed form, a semi-analytic ODE, or a second, independently written solver.