Self-interactions can stabilize excited boson stars

Understand

We study the time evolution of spherical, excited ($i.e.$ nodeful) boson star models.

• We consider a model including quartic self-interactions, controlled by a coupling $\Lambda$.
• Performing non-linear simulations of the Einstein-(complex)-Klein-Gordon system, using as initial data equilibrium boson stars solutions of that system, we assess the impact of $\Lambda$ in the stability properties of the boson stars.
• In the absence of self-interactions ($\Lambda=0$), we observe the known behaviour that the excited stars in the (candidate) stable branch decay to a non-excited star without a node; however, we show that for large enough values of the self-interactions coupling, these excited stars do not decay (up to timescales of about $t\sim 10^4$).