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Gravitational waves could prove the existence of the quark-gluon plasma

Computer models of merging neutron stars predicts how to tell when this happens

April 30, 2020
Goethe University Frankfurt
According to modern particle physics, matter produced when neutron stars merge is so dense that it could exist in a state of dissolved elementary particles. This state of matter, called quark-gluon plasma, might produce a specific signature in gravitational waves. Physicists have now calculated this process using supercomputers.

Neutron stars are among the densest objects in the universe. If our Sun, with its radius of 700,000 kilometres were a neutron star, its mass would be condensed into an almost perfect sphere with a radius of around 12 kilometres. When two neutron stars collide and merge into a hyper-massive neutron star, the matter in the core of the new object becomes incredibly hot and dense. According to physical calculations, these conditions could result in hadrons such as neutrons and protons, which are the particles normally found in our daily experience, dissolving into their components of quarks and gluons and thus producing a quark-gluon plasma.

In 2017 it was discovered for the first time that merging neutron stars send out a gravitational wave signal that can be detected on Earth. The signal not only provides information on the nature of gravity, but also on the behaviour of matter under extreme conditions. When these gravitational waves were first discovered in 2017, however, they were not recorded beyond the merging point.

This is where the work of the Frankfurt physicists begins. They simulated merging neutron stars and the product of the merger to explore the conditions under which a transition from hadrons to a quark-gluon plasma would take place and how this would affect the corresponding gravitational wave. The result: in a specific, late phase of the life of the merged object a phase transition to the quark-gluon plasma took place and left a clear and characteristic signature on the gravitational-wave signal.

Professor Luciano Rezzolla from Goethe University is convinced: "Compared to previous simulations, we have discovered a new signature in the gravitational waves that is significantly clearer to detect. If this signature occurs in the gravitational waves that we will receive from future neutron-star mergers, we would have a clear evidence for the creation of quark-gluon plasma in the present universe."

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Materials provided by Goethe University Frankfurt. Note: Content may be edited for style and length.

Journal Reference:

  1. Lukas R. Weih, Matthias Hanauske, Luciano Rezzolla. Post-merger gravitational wave signatures of phase transitions in binary mergers. Physical Review Letters, 2020 DOI: 10.1103/PhysRevLett.124.171103

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Goethe University Frankfurt. "Gravitational waves could prove the existence of the quark-gluon plasma." ScienceDaily. ScienceDaily, 30 April 2020. <>.
Goethe University Frankfurt. (2020, April 30). Gravitational waves could prove the existence of the quark-gluon plasma. ScienceDaily. Retrieved May 29, 2024 from
Goethe University Frankfurt. "Gravitational waves could prove the existence of the quark-gluon plasma." ScienceDaily. (accessed May 29, 2024).

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