Radial kinks in the boson stars

TL;DR

The paper investigates how radial domain-wall-like kinks evolve in curved spacetimes by placing a probe kink on backgrounds generated by spherical massive and solitonic boson stars. It uses two scalar potentials to form compact, self-gravitating stars and analyzes kink dynamics under a fixed background, highlighting the role of compactness $\\mathcal{C}$ in slowing the kink's approach to the origin and in producing transient post-collision kinks, including outward-moving ones in highly compact cases. The findings suggest that kink dynamics could act as a probe of interior structures of dense astrophysical objects, potentially informing black-hole interiors, though the study is limited to the probe regime without backreaction. Overall, the work adds a dynamical diagnostic tool for studying compact objects via topological defects in curved spacetimes.

Abstract

In this work, we study the time evolution of radial kinks in the background of boson stars. In particular, we consider two types of boson stars: the massive boson star and the solitonic boson star. For each boson star, we study the dynamics of the kinks with four different compactnesses. We observe that the greater the compactness is, the slower the kinks move towards the origin of the boson stars, indicating that the compactness will hinder the kinks to collide with the origin. Additionally, it is found that when the boson star is highly compact, a new kink may turn out after the kink colliding with the origin, instead of immediately dissipating into the background. We then propose that the radial kinks may potentially serve as a means to probe the internal structures of dense astrophysical objects, even the interior structure of black holes.

Figures (7)

• Figure 1: Background configurations $A(r)$, $B(r)$ and the scalar field $\phi(r)$ in the massive boson star with four different compactnesses $\mathcal{C}$ = 0.043562, 0.096822, 0.137524 and 0.162703.
• Figure 2: Background quantities for the metric coefficients $A(r)$, $B(r)$ and the scalar field $\phi(r)$ of solitonic boson stars with four different compactnesses $\mathcal{C}$ = 0.061873, 0.106370, 0.195134 and 0.248817.
• Figure 3: Time evolutions of the scalar field $\phi_k$ in massive boson stars with four different compactness. In each panel, the scalar field shares the same initial configuration of the kink at position $r_k(0)=30$. In each panel, the upper plots show the kink evolutions (solid lines) before they collide with the origin, while the lower plots show the dynamics after the collision (dash-dotted lines).
• Figure 4: Time evolution of kink positions $r_k$ in massive boson star before they collide with the origin, with four different compactnesses. The black curve shows the reference evolution in Minkowskian spacetime. All cases share the same initial kink positions at $r_k(0)=30$ and initial zero velocities.
• Figure 5: Time evolutions of the scalar field $\phi_k$ in solitonic boson stars with four different compactness. In each panel, the scalar field shares the same initial configuration of the kink at position $r_k(0)=30$. In each panel, the upper plots show the kink evolutions (solid lines) before they collide with the origin, while the lower plots show the dynamics after the collision (dash-dotted lines).