NSC++: Non-standard cosmologies in C++

Abstract

We introduce NSC++, a header-only C++ library that simulates the evolution of the plasma and a decaying fluid in the early Universe. NSC++ can be used in C++ programs or called directly from python scripts without significant overhead. There is no special installation process or external dependencies. Furthermore, there are example programs that can be modified to handle several cases. Program summaryProgram title:NSC++CPC Library link to program files:https://doi.org/10.17632/yn883k4wsr.1Developer's repository link:https://github.com/dkaramit/NSCppProgramming language:C++ (C++17+) and python (3.7+).Licensing provisions: MIT license.Nature of problem: Solves equations that describe the evolution of the plasma along with a fluid that increases the entropy of the plasma during the early Universe.Solution method: Embedded Runge-Kutta for the numerical integration of the system of differential equations. The user can choose between explicit and Rosenbrock methods. There are several of Butcher tableaux already implemented, but the user can implement their own. The interpolations of the relativistic degrees of freedom are accomplished by cubic spline interpolation.Additional comments including restrictions and unusual features: The value of the pressure over the energy density and the energy loss parameter of the fluid are assumed to be constant. It is also assumed that there is no energy leaking from the plasma to the fluid.