Malaise and remedy of binary boson-star initial data

Through numerical simulations of boson-star head-on collisions, we explore the quality of binary initial data obtained from the superposition of single-star spacetimes. Our results demonstrate that evolutions starting from a plain superposition of individual boosted boson-star spacetimes are vulnerable to significant unphysical artefacts. For equal-mass binaries, these difficulties can be overcome with a simple modification of the initial data suggested in Helfer et al (2019 Phys. Rev. D 99 044046) for collisions of oscillations. While we specifically consider massive complex scalar field boson star models of very high and low compactness, we conjecture that this vulnerability be also present in other kinds of exotic compact systems and hence needs to be addressed.

Automated summary

This study investigates the head-on collisions of boson stars through numerical simulations and explores the quality of binary initial data obtained from the superposition of single-star spacetimes. The results show that plain superposition of individual boosted boson-star spacetimes can lead to significant unphysical artefacts. A modification of the initial data proposed by Helfer et al in 2019 is effective in overcoming these difficulties for equal-mass binaries. Furthermore, the vulnerability observed in this study may also be present in other exotic compact systems.