Lowest-order relativistic interaction between lattice vibrations and internal degrees of freedom of a nucleus

A moving nucleus experiences a Lorentz contraction and spin rearrangement due to relativity. A nucleus that oscillates in a molecule or solid due to vibrations will undergo minor relativistic modifications which are a result of the vibrations, indicative of a relativistic phonon-nuclear interaction. The derivation of the lowest-order interaction from the many-particle Dirac model is reviewed. The Dirac model with a realistic potential model is not covariant, which is a source of concern. The lowest-order phonon-nuclear interaction obtained from a covariant two-body Bethe-Salpeter model is found to be similar to the interaction obtained from the Dirac model, supporting the notion that the interaction is not an artifact. Matrix elements of the lowest-order interaction are expressed in terms of one-body operators, which facilitates evaluation and allows for quantitative estimates of the magnitude.

Automated summary

A moving nucleus undergoes Lorentz contraction and spin rearrangement due to relativity. Vibrations in a molecule or solid cause minor relativistic modifications in a oscillating nucleus, indicating a relativistic phonon-nuclear interaction. The derivation of the lowest-order interaction is reviewed using the many-particle Dirac model. The lowest-order phonon-nuclear interaction obtained from the covariant two-body Bethe-Salpeter model is similar to the interaction obtained from the Dirac model, indicating that it is not an artifact. Matrix elements of the lowest-order interaction are expressed in terms of one-body operators, facilitating evaluation and quantitative estimation of the magnitude.