On density and temperature-dependent ground-state and continuum effects in the equation of state for stellar interiors -- A Comment on the paper by S. Arndt, W. Dappen and A. Nayfonov 1998, ApJ 498, 349

We examine the consequence of shifts in bound-state energies, as well as the position of the continuum for thermodynamic quantities. Two independent methods from different branches of physics are brought together. A simple free-energy model is used to examine the thermodynamic consequences of the results of quantum statistical calculations of two-particle properties in a plasma using the Green's function technique. A comparison with data inferred from helioseismology shows that our interdisciplinary procedure works very well for lower level approximations, such as the static screening in the effective two-particle wave equation. However, in the case of dynamic screening in the wave equation, the resulting thermodynamic quantities are inconsistent with observations. This could result from the inability of our method to compute the thermodynamic quantities or from the inappropriate treatment of the ion contribution to the electronic self-energy corresponding to the dielectric function used in random phase approximation. In any case, the results superbly demonstrate the power of helioseismology to test models of basic plasma physics.