This paper studies how the internal makeup of hypothetical “strange quark stars” can influence a phenomenon called spontaneous scalarization in an alternative theory of gravity. Strange quark stars are theoretical compact stars made mostly of deconfined quarks. The relationship between pressure and density inside such a star is called an equation of state (EoS). The authors ask how different plausible quark matter EoS choices change whether and how a separate scalar field appears inside the star.

To answer this, the researchers build stellar models in scalar-tensor gravity, a class of theories that adds a scalar field to Einstein’s gravity. In such theories a scalar field can remain small in weak gravity but grow suddenly inside a compact star — a process called spontaneous scalarization. That growth gives the star a “scalar charge,” which can change the star’s structure and the pattern of gravitational waves it would emit. The authors compute scalarized strange quark star models for three types of quark matter in simple bag-model descriptions: Normal quark matter, color-flavor-locked (CFL) superconducting quark matter, and a variant labelled CFLm. They vary parameters such as the effective bag constant, a perturbative quantum chromodynamics (QCD) correction, the CFL pairing gap, and the strange-quark mass, and then solve for mass–radius curves, the central scalar field strength, scalarization thresholds, and the resulting scalar charge.

At a high level, the study shows that those microphysical parameters control both the macroscopic star size and mass and the tendency of the star to scalarize. For example, changing the effective bag constant or the pairing gap shifts the mass–radius relation and the central scalar field value at which scalarization appears. The scalar charge and the threshold where scalarization turns on also depend on these EoS choices. Because scalar charges produce dipole gravitational radiation in binaries, these differences could in principle be seen in gravitational-wave or combined electromagnetic and gravitational observations.