Forced thermalization for certain regions is applied if the corresponding Forced_Thermalization section is present in the configuration file.

Mandatory keys

Cell_Number — list of 3 ints, required

Number of cells in each direction (x,y,z).

Critical_Edens — double, required

Critical energy density in GeV/fm³ above which forced thermalization is applied.

Start_Time — double, required

Time in fm after which forced thermalization may be applied, if the energy density is sufficiently high.

Timestep — double, required

Timestep of thermalization in fm.

Optional keys

Algorithm — string, optional, default = "biased BF"

Algorithm applied to enforce thermalization, see Oliinychenko:2016vkg [41] for more details.

"unbiased BF" → slowest, but theoretically most robust
"biased BF" → faster, but theoretically less robust
"mode sampling" → fastest, but least robust

Lattice_Sizes — list of 3 doubles, required

The lattice is placed such that the center is [0.0,0.0,0.0]. If one wants to have a central cell with center at [0.0,0.0,0.0] then number of cells should be odd (2k+1) in every direction.

Lattice_Sizes is required for all modi, except the "Box" modus. In case of "Box" modus, the lattice is set up automatically to match the box size, and the user should not (and is not allowed to) specify it. Sizes are to be specified in fm.

Microcanonical — bool, optional, default = false

Enforce energy conservation or not as part of sampling algorithm. Relevant for biased and unbiased Becattini-Ferroni (BF) algorithms. If this option is on, samples with energies deviating too far from the initial one will be rejected. This is different from simple energy and momentum renormalization, which is done in the end anyway. If energy conservation is enforced at sampling, the distributions become microcanonical instead of canonical. One particular effect is that multiplicity distributions become narrower.

The downside of having this option on is that the sampling takes significantly longer time.

Configuring forced thermalization

The following example activates forced thermalization in cells in which the energy density is above 0.3 GeV/fm³. The lattice is initialized with 21 cells in x and y direction and 101 cells in z-direction. The lattice size is 20 fm in x and y direction and 50 fm in z-direction. The thermalization is applied only for times later than 10 fm with a timestep of 1 fm. The sampling is done according to the "biased BF" algorithm.

Forced_Thermalization:
    Lattice_Sizes: [20.0, 20.0, 50.0]
    Cell_Number: [21, 21, 101]
    Critical_Edens: 0.3
    Start_Time: 10.0
    Timestep: 1.0
    Algorithm: "biased BF"