Synopsis

Phonons in a Stellar Crust

Physics 4, s162
A theoretical description of phonon interactions in the crust of neutron stars could help interpret observations of the stars’ thermal and mechanical properties.
Wikipedia Commons

The density of nuclear matter in a neutron star is fourteen orders of magnitude greater than any material on Earth, but this matter can undergo phase transitions similar to those found in normal solids. In a paper appearing in Physical Review C, Vincenzo Cirigliano and colleagues at Los Alamos National Laboratory in New Mexico present a theoretical description of phonon interactions in the exotic phases of matter found in neutron stars, which play a role in the stars’ physical properties.

The inner crust of a neutron star, which is of order a kilometer thick, is a mixture of electrons, neutrons, and ionized nuclei. According to theory, quantum effects and the interplay of nuclear and Coulomb forces between the particles can lead to the formation and coexistence of two phases: an ordered lattice of ionized nuclei and a neutron superfluid. Observational studies of accreting and magnetized neutron stars are increasingly sensitive to the properties of the crust and have motivated renewed interest in this two-phase state.

According to Cirigliano et al., interactions between neutrons and protons couple the oscillations (phonons) associated with the ionic lattice and the superfluid. A better understanding of this mixing of phonons may affect predictions of how the crust responds to thermal or mechanical perturbations. For example, in highly magnetized neutron stars called magnetars, the theory suggests there are limits to how anisotropic the temperature of the star can be.

The theory may also apply to terrestrial systems, as ongoing cold-atom experiments seek to achieve similar crystalline-superfluid phases. – Benjamin F. Gibson and Joseph I. Kapusta


Subject Areas

Nuclear Physics

Related Articles

Fusion Turns Up the Heat
Energy Research

Fusion Turns Up the Heat

A laser-fusion scheme has achieved ignition—an important step on the road to energy production. Read More »

Precision Nuclear Probes for New Physics
Nuclear Physics

Precision Nuclear Probes for New Physics

Tests of the standard model of particle physics using nuclear isotopes are becoming increasingly precise but they have a way to go before they can confirm the existence of any new particles. Read More »

The Higgs Boson: A Theory, An Observation, A Tool
Nuclear Physics

The Higgs Boson: A Theory, An Observation, A Tool

With her firm belief in the standard model, physicist Manuella Vincter was confident that the Higgs boson would be seen at the Large Hadron Collider (LHC). She’s less sure about what might come next. Read More »

More Articles