freestream-milne (c) Derek Everett

Purpose

freestream-milne numerically solves the collisionless Boltzmann Equation assuming that

1. the particles are massless
2. initial distribution function is isotropic in azimuthal momentum space $px, py$
3. the initial distribution is a gaussian $(y - \eta)$ in 3D case, or delta function in $(y-\eta)$ in 2D case.

Given an initial energy density profile $T^{00}$, it computes the stress energy tensor $T^{\mu\nu}$ at a later time, and also a viscous hydrodynamic decomposition.

OpenMP is used to accelerate the computation.

Usage

Parameters and options can be set in freestream_input, which is read in at run time. They are described below OUTPUTFORMAT (int) 1 : disk , 2 : write to vectors in memory

BARYON (int) 0 : freestream the energy density, 1 : freestream the baryon density and energy density

IC_ENERGY (int) 1 : Smooth Gaussian, 2 : MC Guassian, 3: read tab delimited file for energy density, 4 : read superMC block format, 5 : read from vector in Memory

IC_BARYON (int) 1 : Smooth Gaussian, 2 : MC Guassian, 3: read tab delimited file for baryon density

ETA_WIDTH (float) used to create a 3D profile of energy density from 2D MC Glb (only for superMC block)

ETA_FLAT (float) used to create a 3D profile of energy density from 2D MC Glb (only for superMC block)

SIGMA (float) std. deviation of one particle distribution function f ~ exp((y - eta)^2 / 2 SIGMA^2)

SIGMA_B (float) std. deviation of one particle distribution function of baryon charges f_B ~ exp((y - eta)^2 / 2 SIGMA_B^2)

DIM_X (int) number of grid points in x

DIM_Y (int) number of grid points in y

DIM_ETA (int) number of grid points in eta

DIM_RAP (int) number of grid points in rapidity for riemann sum

DIM_PHIP (int) number of grid points in phi_p for riemann sum

DX (float) lattice spacing in x [fm]

DY (float) lattice spacing in y [fm]

DETA (float) lattice spacing in eta

DRAP (float) lattice spacing in rapidity (differential) DEPRECATED

DTAU (float) free streaming proper time interval [fm/c]

TAU0 (float) start of free streaming proper time [fm/c]

EOS_TYPE (int) 1 : conformal EoS, 2 : Wuppertal-Bhudapest Parameterization

E_FREEZE (float) [GeV/fm^3] used to calculate fraction of energy contained within surface of energy density > E_FREEZE