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Browsing by Subject "twin star"

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  • Blomqvist, Sofia (2024)
    The matter in neutron stars exist under extreme conditions, and the cores of these stars harbour densities unreachable in any laboratory setting. Therefore, this unique environment provides an exceptional opportunity to investigate high-density matter, described by the theory of Quantum Chromodynamics (QCD). This thesis centers on the exploration of twin stars, hypothetical compact objects that extend beyond the neutron star sequence. Originating from a first-order phase transition between hadronic matter and quark matter, our focus is on understanding the constraints on these phase transitions and their effect on the observable properties of twin stars. In our investigation of twin stars, we construct a large ensemble of possible equations of state featuring a strong first-order phase transition. We approximate the low- and high-density regions with polytropic form and connect them to chiral effective field theory results at nuclear densities and extrapolated perturbative QCD at high densities. The resulting equations of state are then subjected to astrophysical constraints obtained from high-mass pulsars and gravitational wave detections to verify their compatibility with observations. Within our simple study, we identify two distinct types of twin stars, each providing a clear signature in macroscopic observables. These solutions originate from separate regions in the parameter space, with both regions being relatively small. Twin stars in our approach generally obtain small maximum masses, while the part of the sequence corresponding to neutron stars extends to large radii, indicating that these solutions only marginally pass the astrophysical constraints. Finally, we find that all twin stars obtain sizable cores of quark matter.