Phenomenological Aspects of Isospin Violation in the Nuclear Force

Phenomenological Lagrangians and dimensional power counting are used to assess isospin violation in the nucleon-nucleon force. The $\pi NN$ coupling constants (including the Goldberger-Treiman discrepancy), charge-symmetry breaking, and meson-mixing models are examined. A one-loop analysis of the isospin-violating $\pi NN$ coupling constants is performed using chiral perturbation theory. Meson-mixing models and the $^3$He - $^3$H mass difference are also discussed in the context of naturalness.