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arXiv · 2610.03148

Twins in the Shadow: Phase Transitions in Proto-Neutron Stars

Jannik Milthaler·Jan-Erik Christian·Pia Jakobus·Stephan Rosswog
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Abstract

We study the impact of a first-order phase transition from hadronic to deconfined quark matter on the evolution of proto-neutron stars. To maximize the applicability of our results, we construct an equation of state that is highly parameterizable, where we use a relativistic mean field approach to model hadronic matter and a constant speed of sound approach to model quark matter. We approximate the cooling behavior of proto-neutron stars as a sequence of decreasing entropy at constant baryonic mass. Some parameterizations lead to so-called "twin-stars", where two neutron stars have the same (gravitational) mass but different radii. Detecting them is regarded as a smoking gun signal for phase transition. We find, however, that proto-neutron star evolution suggests that gravitational twin stars are only possible if the hybrid star does not have, in addition, a baryonic twin. This rules out most twin star pairs, especially if the phase transition occurs at large densities. In a mass-radius diagram the unpopulated hybrid branch appears to be "in the shadow" of the hadronic branch.

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Jannik Milthaler, Jan-Erik Christian, Pia Jakobus, Stephan Rosswog. 2026-10-02. Twins in the Shadow: Phase Transitions in Proto-Neutron Stars. https://arxiv.org/abs/2610.03148

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