Malaise and remedy of binary boson-star initial data

TL;DR

This paper investigates the limitations of using simple superpositions for initial data in boson-star collision simulations and proposes a modification to improve physical accuracy across various exotic compact objects.

Contribution

It identifies the unphysical artefacts caused by naive superposition of boson-star spacetimes and introduces a simple initial data modification to mitigate these issues.

Findings

Plain superposition leads to significant unphysical artefacts.

A simple modification improves the physical realism of initial data.

The vulnerability is likely universal across exotic compact systems.

Abstract

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. These difficulties can be overcome with a simple modification of the initial data suggested in [PRD 99 (2018) 044046] for collisions of oscillatons. While we specifically consider massive complex scalar field boson star models up to a 6th-order-polynomial potential, we argue that this vulnerability is universal and present in other kinds of exotic compact systems and hence needs to be addressed.