arXiv subjects

Sitthichai Pinkanjanarod

Publications and source records attributed to Sitthichai Pinkanjanarod.

4 recordsLinked to original sources

arXiv2023

Normal and Quasinormal Modes of Holographic Multiquark Star

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.

gr-qc↗

arXiv2022

Tidal Deformation and Radial Pulsations of Neutron Star with Holographic Multiquark Core

Tidal deformation of neutron star with multiquark core is calculated using nuclear and multiquark equations of state. The equation of state of the multiquark phase from the holographic Sakai-Sugimoto~(SS) model is relatively stiff in the low density region and becomes softer at high densities. The values of Love number and dimensionless deformation parameter, $k_{2}$ and $Λ$, are found to be within the physically viable range under the present constraints. Radial pulsation frequencies of the multiquark core for $n=0-5$ modes are calculated for the entire mass range. For $M_{\rm core}\simeq 2 M_{\odot}$, the fundamental-mode frequency is approximately $2.5$ kHz for the energy density scale $ε_{s}=23.2037$ GeV/fm$^{3}$ of the holographic SS model, this frequency is proportional to $\sqrt{ε_{s}}$.

gr-qc↗

arXiv2021

Slowly Rotating Neutron Star with Holographic Multiquark Core: I-Love-Q Relations

Moment of inertia ($I$), rotational~(tidal) Love number ($λ^{\rm (rot)}$) and quadrupole moment ($Q$) of slowly rotating massive neutron star~(NS) with holographic multiquark~(MQ) core are computed in comparison to pure MQ star. The Chiral Effective Theory~(CET) stiff equation of state~(EoS) is used in the crust of the neutron star. The dimensionless multipole moments $\bar{I},\barλ^{\rm (rot)}, \bar{Q}$ are found to be independent of the rotation parameters and determined completely by the zeroth-order star profile. Universal ``I-Love-Q'' relations found by Yagi and Yunes [1,2] are mostly preserved even in the presence of the MQ core. Tidal deformation parameter $\barλ^{\rm (tid)}$ is also explored in connection with $\bar{I}, \barλ^{\rm (rot)}, \bar{Q}$, two kinds of universal I-Love-Q relations are verified. However, the unique kink in the plots of multipoles with respect to mass and compactness of the population of neutron stars can reveal the existence of massive NS with the MQ core.

gr-qc↗

arXiv2021

Massive neutron stars with holographic multiquark cores

Phases of nuclear matter are crucial in the determination of physical properties of neutron stars~(NS). In the core of NS, the density and pressure become so large that the nuclear matter possibly undergoes phase transition into a deconfined phase, consisting of quarks and gluons and their colour bound states. Even though the quark-gluon plasma has been observed in ultra-relativistic heavy-ion collisions\cite{Gyulassy, Andronic}, it is still unclear whether exotic quark matter exists inside neutron stars. Recent results from the combination of various perturbative theoretical calculations with astronomical observations\cite{Demorest, Antoniadis} shows that (exotic) quark matter could exist inside the cores of neutron stars above 2.0 solar masses ($M_{\odot}$)~\cite{Annala:2019puf}. We revisit the holographic model in Ref.~\cite{bch, bhp} and implement the equation of states~(EoS) of multiquark nuclear matter to interpolate the pQCD EoS in the high-density region with the nuclear EoS known at low densities. For sufficiently large energy density scale~($ε_{s}$) of the model, it is found that multiquark phase is thermodynamically prefered than the stiff nuclear matter above the transition points. The NS with holographic multiquark core could have masses in the range $1.96-2.23~(1.64-2.10) M_{\odot}$ and radii $14.3-11.8~(14.0-11.1)$ km for $ε_{s}=26~(28)$ GeV/fm$^{3}$ respectively. Effects of proton-baryon fractions are studied for certain type of baryonic EoS; larger proton fractions could reduce radius of the NS with multiquark core by less than a kilometer.

nucl-th↗