The virial equation of state of low-density neutron matter

C. J. Horowitz, A. Schwenk

Research output: Contribution to journalArticlepeer-review

85 Scopus citations


We present a model-independent description of low-density neutron matter based on the virial expansion. The virial equation of state provides a benchmark for all nuclear equations of state at densities and temperatures where the interparticle separation is large compared to the thermal wavelength. We calculate the second virial coefficient directly from the nucleon-nucleon scattering phase shifts. Our results for the pressure, energy, entropy and the free energy correctly include the physics of the large neutron-neutron scattering length. We find that, as in the universal regime, thermodynamic properties of neutron matter scale over a wide range of temperatures, but with a significantly reduced interaction coefficient compared to the unitary limit.

Original languageEnglish
Pages (from-to)153-159
Number of pages7
JournalPhysics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics
Issue number2-3
StatePublished - 6 Jul 2006
Externally publishedYes

Bibliographical note

Funding Information:
This work is supported by the US Department of Energy under Grant No. DE-FG02-87ER40365 and the National Science Foundation under Grant No. PHY-0244822.


  • Equation of state
  • Low-density neutron matter
  • Virial expansion


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