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Tripling Fluctuations and Peaked Sound Speed in Fermionic Matter.
Hiroyuki Tajima1,2,3, Kei Iida2,4,5, Toru Kojo6
1The University of Tokyo, Department of Physics, Graduate School of Science, Tokyo 113-0033, Japan.
Physical Review Letters
|August 12, 2025
Summary
Researchers explored three-fermion clusters and their role in the hadron-quark crossover, potentially explaining neutron star dense-matter equations of state. This study reveals how cluster formation influences matter properties at extreme densities.
Area of Science:
- Nuclear Physics
- Astrophysics
- Condensed Matter Physics
Background:
- The hadron-quark crossover is crucial for understanding dense matter in neutron stars.
- Recent observations of neutron star masses and radii provide constraints on the dense-matter equation of state.
Purpose of the Study:
- To investigate the mechanism of the hadron-quark crossover.
- To understand the role of tripling fluctuations and three-fermion cluster formation in this process.
Main Methods:
- Examining fluctuations induced by three-fermion cluster formation.
- Utilizing a phase-shift representation of fluctuations.
- Applying the approach to a one-dimensional three-color fermion system.
Main Results:
- Fluctuations show an interplay between bound and scattering states.
- Nonmonotonic momentum distributions of baryonlike clusters were observed.
- A peaked sound speed at finite densities was identified.
Conclusions:
- Three-fermion clusters and associated fluctuations are key to the hadron-quark crossover.
- The model reproduces aspects of the dense-matter equation of state relevant to neutron stars.
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