Normal and Quasinormal Modes of Holographic Multiquark Star

TL;DR

This paper calculates the normal and quasinormal mode frequencies of multiquark stars, revealing signatures of high-density cores and providing detailed gravitational wave mode characteristics for different star masses.

Contribution

It introduces methods to compute both normal and quasinormal modes of multiquark stars, highlighting distinctive frequency jumps at core transitions and detailed mode properties.

Findings

Mode frequencies jump at high-density core transition

Small imaginary QNMs have frequencies 1.5-2.6 kHz with damping times 0.19-1.7 s

Large imaginary QNMs have frequencies 5.98-9.81 kHz with damping times 0.13-0.46 ms

Abstract

The quadrupole normal-mode oscillation frequency $f_{n}$ of multiquark star are computed for $n=1-5$. At the transition from low to high density multiquark in the core region, the first 2 modes jump to larger values, a distinctive signature of the presence of the high-density core. When the star oscillation couples with spacetime, gravitational waves~(GW) will be generated and the star will undergo damped oscillation. The quasinormal modes~(QNMs) of the oscillation are computed using two methods, direct scan and WKB, for QNMs with small and large imaginary parts respectively. The small imaginary QNMs have frequencies $1.5-2.6$ kHz and damping times $0.19-1.7$ secs for multiquark star with mass $M=0.6-2.1 M_{\odot}$~(solar mass). The WKB QNMs with large imaginary parts have frequencies $5.98-9.81$ kHz and damping times $0.13-0.46$ ms for $M\simeq 0.3-2.1 M_{\odot}$. They are found to be the fluid $f-$modes and spacetime curvature $w-$modes respectively.