Version 1.5.2

Version 1.5.2

Date: 2025-07-23

This update mainly fixes a couple of bugs in event generator mode (thanks to @aohlson).
Namely, it fixes a bug causing an infinite loop in the event generator when the number of particles in the event is zero.
This can happen when simulating low-multiplicity proton-proton collisions with local charge conservation.
It also fixes an issue with initialization of Breit-Wigner distributions in the event generator, which could cause invalid_argument exceptions.

Bugfixes

• Fixed a bug in the event generator causing an infinite loop when the number of particles in the event is zero.
• Fixed an issue with initialization of Breit-Wigner distributions by properly checking if the width is zero.

Enhancements

• Implemented $m \to 0$ limit for quantum statistics calculations using cluster expansion.
• Added additional flag checks for ThermalModelCanonical calculations.

Full Changelog: v1.5.1...v1.5.2

Version 1.5.1

Version 1.5.1

Date: 2025-07-06

Bugfixes

• Fixed the setting of meson–meson and meson–baryon interactions in the GUI (it was opposite to what was selected)
• Corrected pressure and energy density calculation for mixed-canonical ensembles.

Other changes

• GUI updates: extended range for $n_B/s$ and added factorial cumulant option.
• Updated build workflows.
• Various documentation and typo fixes.

Version 1.5

Date: 2024-03-22

Version 1.5 contains a number of new features and improvements.

Real gas HRG

This version contains a first complete version of real gas HRG.
Real gas is a generalization of the van der Waals HRG.
It implements a generalization of the excluded volume prescription by considering non-linear EV prescriptions, such as Carnahan-Starling EoS.
It also allows one to incorporate arbitrary mean fields which can be a function of all densities in the system.
This allows one to model the effects of interactions in dense regime, such as in neutron stars.

A real gas model for a single component case has been formulated in Vovchenko, Phys. Rev. C 96, 015206 (2017) while a paper detailing the formulation of the model for multiple components is in preparation.

Real gas HRG is implemented as a new ThermalModelRealGas class.
It takes as input the excluded volume model and the mean field model, both of which can be arbitrary.
The source code contains a number of examples of both models, such as van der Waals/Carnahan-Starling excluded volume, and van der Waals or baryon density dependent mean field.

Real gas HRG fully supports the calculation of all the standard thermodynamic quantities and susceptibilities and has the complete functionality of van der Waals HRG model from before.

See examples ThermodynamicsBQS.cpp and SusceptibilitiesBQS.cpp which include Real Gas HRG option and this link for documentation.

Cosmic trajectories

This version contains an implementation of cosmic trajectories in the Early Universe, given baryon, charge, lepton flavor asymmetries.

• Reference: Vovchenko et al., Phys. Rev. Lett. 126, 012701 (2021).
• Class: CosmicEoS
• Documentation: this link
• Example: this link
• GUI: Equation of state tab
• Implements the EoS of HRG + leptons + photons
• Computes trajectories in the space of B, Q, and lepton flavor chemical potentials

Other new features

• Partial chemical equilibrium with baryon annihilation

  This version contains an implementation of partial chemical equilibrium with baryon annihilation, namely $B\bar{B} \leftrightarrow n\pi$ reaction, where $n$ is a parameter~(typically $n = 5$), which can be utilized in thermal fits.

  • Class: ThermalModelPCEAnnihilation.
  • Reference: Vovchenko, Koch, Phys. Lett. B 835, 137577 (2022).
  • Documentation: this link

• Neutron star matter calculations

  • Supported by adding leptons to the list from /input/list/electroweak and setting charge neutrality and $\mu_S = 0$
  • For a meaningful calculation, one should use an interacting version of the HRG, e.g. real gas
  • Example here

• Effective mass model for pions

  • Repulsive interactions and Bose-Einsten condensation
  • Described in https://arxiv.org/abs/2004.09004

• Magnetic field

  • HRG model in the magnetic field as formulated in https://arxiv.org/abs/1301.1307
  • Additional features: Hadron number densities and fluctuations
  • GUI: PCE/Saha/Other... configuration
  • Reference: Vovchenko, Phys. Rev. C 110, 034914 (2024)

• New thermodynamic quantities

  • Temperature derivatives of the energy, entropy and hadron number densities
  • Temperature derivatives of susceptibilities
  • Hessian matrix of the pressure wrt $T$ and $\mu$'s
  • Adiabatic and isothermal sound velocity (with multiple conserved charges and specific entropies)
  • Specific heat capacity $c_V/T^3$

Event generator

• Shear and bulk viscous corrections
  • Part of FIST sampler (see also https://github.com/vlvovch/fist-sampler)
  • Currently no excluded volume and bulk viscosity simultaneously
  • Thanks to: @JanHammelmann and @NGoetz
• Support for output to SMASH
• Propagation of particles after (weak) decays and DCA cuts

New examples

• Cosmic trajectories
• Neutron star matter EoS at T = 0
• Thermodynamic functions in $(T, \mu_B, \mu_Q, \mu_S)$ phase diagram
• Susceptibilities, speed of sound, and heat capacity in $(T, \mu_B, \mu_Q, \mu_S)$ phase diagram

Technical improvements

• New logo
• GUI supports and uses Qt6 by default now
  • Qt5 still works but not will not be guaranteed to work in the future
• Linear algebra: Migrated to Eigen-3.4.0
• GitHub actions for automated tests/compilation on various platforms
• Expanded unit tests
• Better warning and error handling
• Various fixes of minor errors

GUI enhancements

• Calculations within real gas HRG (in the model selection)
• Baryon annihilation in PCE (PCE/Saha/Other...)
• Effective mass model for pions (PCE/Saha/Other...)
• Tabular view of calculation in the EoS tab and export to file (Equation of state tab)
• Calculation of cosmic trajectories (Equation of state tab)
• Calculations at fixed conserved charge densities (instead of fixed $\mu$'s) (Use densities checkbox in Thermal model tab)
• Various enhancements

Full Changelog: v.1.4.2...v1.5

Version v1.4.2

Date: 2022-11-07

• Fix bug (introduced in v1.4.1) with the normalization of two-particle susceptibilities in ThermalModelIdeal

Version v1.4.1

Date: 2022-10-18

• GUI: Added more clarity concerning the loading of the decays list
• GUI: Number of known decays channels shown in the table for unstable hadrons
• Added explicit calculation of Fermi-Dirac integrals at T = 0

Version v1.4

Date: 2022-08-25

Main new feature: Excluded volume effect in the Monte Carlo event generator

Enhancements

• Hard-core repulsion in event generator (see FIST sampler)
• Crossterms EV-HRG model is now implemented as partial case of QvdW-HRG model (for a = 0)
• GUI: Blast-wave model: Option to set the value of parameter r_max (the maximim transverse radius)
• GUI: Minor improvements for PCE-HRG model thermal fits

Bugfixes

• GUI: Fix bug with the sign of strongly intensive quantity Delta
• GUI: Options for different treatments of hard-core repulsion in event generator

Version 1.3.4

This release fixes a bug with some calculations of scaled moments and Pearson correlation coefficients in GUI that were introduced with the previous release 1.3.3

Version 1.3.3

Date: 2022-05-03

GUI: Added scaled moments and Pearson correlation coefficients into the correlations dialog

Version 1.3.2

Date: 2022-02-18

Minor enhancements and bugfixes

Enhancements

• GUI: Binning options in event generator
• GUI: Ability to add resonances and other particles to online analysis
• GUI: Export Monte Carlo momentum distributions to file
• Event generator: Monte Carlo sampler of ideal HRG from an arbitrary (numerical) hypersurface
• Event generator: Event generator output through a new event writer class
• Event generator: Experimental support for HepMC format
• Lists: Checks the list for particles with non-zero strangeness/charm but zero strangeness/charm quark content and outputs warnings

Bugfixes

• Fix the ordering of p0 and px,py,pz output in ascii event generator output. Was px,py,pz,p0, now it is p0,px,py,pz which is consistent with the header line
• Strangeness/charm neutrality equations will now be solved properly for lists with incorrect zero |s| and |c| columns

Version 1.3.1

Date: 2021-05-26

Minor enhancements and bugfixes

Enhancements

• GUI: Output moments in addition to susceptiblities in the correlations dialog, output nudyn and D measure in equation of state tab
• GUI: Show lattice data for ratios of quantities for the equation of state tab in the GUI, where available
• GUI: Display mean pT in the event generator tab
• Event generator: Sampling of the space-time coordinates in addition to the momenta (not yet supported for the Siemens-Rasmussen model)
• Event generator: Write the output in the format tailor for UrQMD afterburner from https://github.com/jbernhard/urqmd-afterburner
• Event generator: Output particle energy (p0) by default when writing to file

Bugfixes

• Fix the flag setting in ThermalModelPCE for the Saha equation mode and the freeze-out of long-lived resonances
• GUI: Fix the output of strongly intensive quantities for net-particle correlations
• Event generator: Correct resonance mass-energy rescaling when masses of decay products exceed the mass of a resonance
• Add contributions of the K0S decays to the inclusive (weak decay included) yields of pions. Note that decay contributions from K0L are not included