Bubbleprofiler: Finding the field profile and action for cosmological phase transitions

We present BubbleProfiler, a C++ software package for finding field profiles in bubble walls and calculating the bounce action during phase transitions involving multiple scalar fields. Our code uses a recently proposed perturbative method for potentials with multiple fields and a shooting method for single field cases. BubbleProfiler is constructed with modularity, flexibility and practicality in mind. These principles extend from the input of an arbitrary potential with multiple scalar fields in various forms, through the code structure, to the testing suite. After reviewing the physics context, we describe how the methods are implemented in BubbleProfiler, provide an overview of the code structure and detail usage scenarios. We present a number of examples that serve as test cases of BubbleProfiler and comparisons to existing public codes with similar functionality. We also show a physics application of BubbleProfiler in the scalar singlet extension of the Standard Model of particle physics by calculating the action as a function of model parameters during the electroweak phase transition. BubbleProfiler completes an important link in the toolchain for studying the properties of the thermal phase transition driving baryogenesis and properties of gravitational waves in models with multiple scalar fields. The code can be obtained from: https://github.com/bubbleprofiler/bubbleprofiler. Program summary: Program title: BubbleProfiler Program files doi: http://dx.doi.org/10.17632/82y283ftz7.1 Licensing provisions: GPLv3 Programming language: C++ External routines: Boost library, Eigen library, GNU Scientific Library, NLopt library, GiNaC library Nature of problem: Find the field profile in the bubble wall (bounce solution) and Euclidean action for a cosmological phase transition by solving a set of coupled differential equations. Solution method: Direct shooting method for single field problems. Multiple field problems are solved using a perturbative algorithm which linearizes the bounce equations. Restrictions: Currently unable to find bounce solutions for potentials of more than one fields where the vacua are nearly degenerate — these are the so-called “thin walled” cases. Additional comments: Program Github repository https://github.com/bubbleprofiler/bubbleprofiler