smash::SphereModus Class Reference

#include <spheremodus.h>

SphereModus: Provides a modus for expanding matter calculations.

Matter is put in a sphere of radius R with uniform density; isotropic thermal momenta are typically used for initialization, although other initial momentum states are also included, see Bazow:2016oky and Tindall:2016try

To use this modus, choose

General:
     Modus: Sphere

in the configuration file.

Options for SphereModus go in the "Modi"→"Sphere" section of the configuration:

Modi:
     Sphere:
             # definitions here

The following configuration options are understood: Sphere

Definition at line 47 of file spheremodus.h.

Inheritance diagram for smash::SphereModus:

Collaboration diagram for smash::SphereModus:

Public Member Functions
	SphereModus (Configuration modus_config, const ExperimentParameters &parameters)
	Constructor. More...
double	initial_conditions (Particles *particles, const ExperimentParameters &parameters)
	Generates initial state of the particles in the system according to specified parameters: number of particles of each species, momentum and coordinate space distributions. More...
Public Member Functions inherited from smash::ModusDefault
int	impose_boundary_conditions (Particles *, const OutputsList &={})
	Enforces sensible positions for the particles. More...
int	total_N_number () const
int	proj_N_number () const
bool	cll_in_nucleus () const
bool	is_collider () const
double	impact_parameter () const
double	velocity_projectile () const
double	velocity_target () const
FermiMotion	fermi_motion () const
double	max_timestep (double) const
double	length () const
Grid< GridOptions::Normal >	create_grid (const Particles &particles, double min_cell_length, CellSizeStrategy strategy=CellSizeStrategy::Optimal) const
	Creates the Grid with normal boundary conditions. More...

Private Attributes
double	radius_
	Sphere radius (in fm/c) More...
double	sphere_temperature_
	Temperature for momentum distribution (in GeV) More...
const double	start_time_ = 0.
	Starting time for the Sphere. More...
const bool	use_thermal_ = false
	Whether to use a thermal initialization for all particles instead of specific numbers. More...
const double	mub_
	Baryon chemical potential for thermal initialization; only used if use_thermal_ is true. More...
const double	mus_
	Strange chemical potential for thermal initialization; only used if use_thermal_ is true. More...
const std::map< PdgCode, int >	init_multipl_
	Particle multiplicities at initialization; required if use_thermal_ is false. More...
std::map< PdgCode, double >	average_multipl_
	Average multiplicities in case of thermal initialization. More...
const SphereInitialCondition	init_distr_
	Initialization scheme for momenta in the sphere; used for expanding metric setup. More...

Friends
std::ostream &	operator<< (std::ostream &, const SphereModus &)
	Writes the initial state for the Sphere to the output stream. More...

Constructor & Destructor Documentation

SphereModus()

smash::SphereModus::SphereModus ( Configuration  modus_config, const ExperimentParameters &  parameters  )

explicit

Constructor.

Takes all there is to take from the (truncated!) configuration object (only contains configuration for this modus).

Parameters

[in]	modus_config	The configuration object that sets all initial conditions of the experiment.
[in]	parameters	Unused, but necessary because of templated initialization

Definition at line 133 of file spheremodus.cc.

    : radius_(modus_config.take({"Sphere", "Radius"})),
      sphere_temperature_(modus_config.take({"Sphere", "Sphere_Temperature"})),
      start_time_(modus_config.take({"Sphere", "Start_Time"}, 0.)),
      use_thermal_(
          modus_config.take({"Sphere", "Use_Thermal_Multiplicities"}, false)),
      mub_(modus_config.take({"Sphere", "Baryon_Chemical_Potential"}, 0.)),
      mus_(modus_config.take({"Sphere", "Strange_Chemical_Potential"}, 0.)),
      init_multipl_(use_thermal_
                        ? std::map<PdgCode, int>()
                        : modus_config.take({"Sphere", "Init_Multiplicities"})
                              .convert_for(init_multipl_)),
      init_distr_(modus_config.take({"Sphere", "Initial_Condition"},
                                    SphereInitialCondition::ThermalMomenta)) {}

Member Function Documentation

initial_conditions()

double smash::SphereModus::initial_conditions	(	Particles *	particles,
		const ExperimentParameters &	parameters
	)

Generates initial state of the particles in the system according to specified parameters: number of particles of each species, momentum and coordinate space distributions.

Susbsequently makes the total 3-momentum 0.

Parameters

[out]	particles	An empty list that gets filled up by this function
[in]	parameters	The initialization parameters of the box

Returns

The starting time of the simulation

Definition at line 167 of file spheremodus.cc.

                                                                               {
  const auto &log = logger<LogArea::Sphere>();
  FourVector momentum_total(0, 0, 0, 0);
  const double T = this->sphere_temperature_;
  /* Create NUMBER OF PARTICLES according to configuration */
  if (use_thermal_) {
    const double V = 4.0 / 3.0 * M_PI * radius_ * radius_ * radius_;
    if (average_multipl_.empty()) {
      for (const ParticleType &ptype : ParticleType::list_all()) {
        if (HadronGasEos::is_eos_particle(ptype)) {
          const double n = HadronGasEos::partial_density(ptype, T, mub_, mus_);
          average_multipl_[ptype.pdgcode()] = n * V * parameters.testparticles;
        }
      }
    }
    double nb_init = 0.0, ns_init = 0.0;
    for (const auto &mult : average_multipl_) {
      const int thermal_mult_int = random::poisson(mult.second);
      particles->create(thermal_mult_int, mult.first);
      nb_init += mult.second * mult.first.baryon_number();
      ns_init += mult.second * mult.first.strangeness();
      log.debug(mult.first, " initial multiplicity ", thermal_mult_int);
    }
    log.info("Initial hadron gas baryon density ", nb_init);
    log.info("Initial hadron gas strange density ", ns_init);
  } else {
    for (const auto &p : init_multipl_) {
      particles->create(p.second * parameters.testparticles, p.first);
      log.debug("Particle ", p.first, " initial multiplicity ", p.second);
    }
  }
  /* loop over particle data to fill in momentum and position information */
  for (ParticleData &data : *particles) {
    Angles phitheta;
    /* thermal momentum according Maxwell-Boltzmann distribution */
    double momentum_radial, mass = data.pole_mass();
    /* assign momentum_radial according to requested distribution */
    switch (init_distr_) {
      case (SphereInitialCondition::IC_ES):
        momentum_radial = sample_momenta_IC_ES(T);
        break;
      case (SphereInitialCondition::IC_1M):
        momentum_radial = sample_momenta_1M_IC(T, mass);
        break;
      case (SphereInitialCondition::IC_2M):
        momentum_radial = sample_momenta_2M_IC(T, mass);
        break;
      case (SphereInitialCondition::IC_Massive):
        momentum_radial = sample_momenta_non_eq_mass(T, mass);
        break;
      case (SphereInitialCondition::ThermalMomenta):
      default:
        mass = HadronGasEos::sample_mass_thermal(data.type(), 1.0 / T);
        momentum_radial = sample_momenta_from_thermal(T, mass);
        break;
    }
    phitheta.distribute_isotropically();
    log.debug(data.type().name(), "(id ", data.id(), ") radial momentum ",
              momentum_radial, ", direction", phitheta);
    data.set_4momentum(mass, phitheta.threevec() * momentum_radial);
    momentum_total += data.momentum();
    /* uniform sampling in a sphere with radius r */
    double position_radial;
    position_radial = std::cbrt(random::canonical()) * radius_;
    Angles pos_phitheta;
    pos_phitheta.distribute_isotropically();
    data.set_4position(
        FourVector(start_time_, pos_phitheta.threevec() * position_radial));
    data.set_formation_time(start_time_);
  }
  /* Make total 3-momentum 0 */
  for (ParticleData &data : *particles) {
    data.set_4momentum(data.momentum().abs(),
                       data.momentum().threevec() -
                           momentum_total.threevec() / particles->size());
  }

  /* Recalculate total momentum */
  momentum_total = FourVector(0, 0, 0, 0);
  for (ParticleData &data : *particles) {
    momentum_total += data.momentum();
    /* IC: debug checks */
    log.debug() << data;
  }
  /* allows to check energy conservation */
  log.debug() << "Sphere initial total 4-momentum [GeV]: " << momentum_total;
  return start_time_;
}

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Member Data Documentation

radius_

double smash::SphereModus::radius_

private

Sphere radius (in fm/c)

Definition at line 78 of file spheremodus.h.

sphere_temperature_

double smash::SphereModus::sphere_temperature_

private

Temperature for momentum distribution (in GeV)

Definition at line 80 of file spheremodus.h.

start_time_

const double smash::SphereModus::start_time_ = 0.

private

Starting time for the Sphere.

Definition at line 82 of file spheremodus.h.

use_thermal_

const bool smash::SphereModus::use_thermal_ = false

private

Whether to use a thermal initialization for all particles instead of specific numbers.

Definition at line 87 of file spheremodus.h.

mub_

const double smash::SphereModus::mub_

private

Baryon chemical potential for thermal initialization; only used if use_thermal_ is true.

Definition at line 92 of file spheremodus.h.

mus_

const double smash::SphereModus::mus_

private

Strange chemical potential for thermal initialization; only used if use_thermal_ is true.

Definition at line 97 of file spheremodus.h.

init_multipl_

const std::map<PdgCode, int> smash::SphereModus::init_multipl_

private

Particle multiplicities at initialization; required if use_thermal_ is false.

Definition at line 102 of file spheremodus.h.

average_multipl_

std::map<PdgCode, double> smash::SphereModus::average_multipl_

private

Average multiplicities in case of thermal initialization.

Saved to avoid recalculating at every event

Definition at line 107 of file spheremodus.h.

init_distr_

const SphereInitialCondition smash::SphereModus::init_distr_

private

Initialization scheme for momenta in the sphere; used for expanding metric setup.

Definition at line 112 of file spheremodus.h.

---

The documentation for this class was generated from the following files:

• src/include/smash/spheremodus.h
• src/spheremodus.cc