Goldstone and pseudo-Goldstone bosons in nuclear, particle and condensed-matter physics

It is a common feature of many physical systems that their behaviour is relatively simple when examined only at low energies (or temperatures) compared to the system's own characterisitic scales. It often happens that there are relatively few states which can participate in low-energy processes, and their interactions can sometimes become less and less important the lower the energies that are examined. Very general theoretical tools exist to …