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Physical Review D

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Multiquark clustering in neutron-star matter from color-spin molecular dynamics

Nobutoshi Yasutake ^1,2,*, Yuta Mukobara ^3,†, Aaron Park^4,‡, Su Houng Lee ^4,§, and Toshiki Maruyama ^2,∥

¹Department of Physics, Chiba Institute of Technology, 2-1-1 Shibazono, Narashino, Chiba 275-0023, Japan
²Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195, Japan
³Department of Transdisciplinary Science and Engineering, School of Environment and Society, Institute of Science Tokyo, Meguro, Tokyo, Japan
⁴Department of Physics and Institute of Physics and Applied Physics, Yonsei University, Seoul 03722, Korea

^*Contact author: nobutoshi.yasutake@p.chibakoudai.jp
^†Contact author: mukobara.y.aa@m.titech.ac.jp
^‡Contact author: aaron.park@yonsei.ac.kr
^§Contact author: suhoung@yonsei.ac.kr
^∥Contact author: maruyama.toshiki@jaea.go.jp

Phys. Rev. D 114, 043050 – Published 19 August, 2026

DOI: https://doi.org/10.1103/154s-hj62

Abstract

We study the equation of state of neutron-star matter with color-spin molecular dynamics. The calculation includes the internal color and spin degrees of freedom and their time evolution. The matter composition, including strangeness under $β$ equilibrium, is determined by energy minimization. We find two main trends. First, within the present color-spin molecular dynamics framework and under the adopted clustering criterion along the stable neutron-star branch, isolated quarklike configurations do not appear; instead, color-magnetic interactions favor the self-consistent formation of multiquark clusters. Within the same criterion, the cluster-size distribution is concentrated at quark numbers that are multiples of three, corresponding to integer baryon numbers. Second, relative to the conventional no- $K^{*}$ baseline, the interaction between strange and light quarks has a strong impact on neutron-star radii. This suggests that future radius measurements, together with phenomenological information on the strangeness-onset density, may help constrain flavor-sector interactions involving strangeness.

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