Head-on collisions of $\ell$-boson stars

Understand

Fully non-linear numerical evolutions of the Einstein-(multi)--Klein-Gordon equations are performed to study head-on collisions of $\ell$-boson stars.

• Despite being spherically symmetric, $\ell$-boson stars have a (hidden) frame of reference, used in defining their individual multipolar fields.
• To assess the impact of their relative orientation, we perform simulations with different angles between the axes of the two colliding stars.
• Additionally, two scenarios are considered for the colliding stars: that they are composites of either the same or different scalar fields.