The relevance of the isospin zero effective interaction

An effort is made to understand the significance of the isospin T = 0 portion on the neutron-proton interaction. The question is investigated within the shell model. Our effective interaction in the shell model comes to us in the form of a collection of two-body matrix elements. The T = 0 portion contains only neutron-proton interaction information while the T = 1 channel contains information from neutron-neutron, protonproton, as well as neutron-proton interactions. A debate in nuclear physics continues as to whether or not there exists neutron-proton pairing, the debate in the T = 0 channel is particularly heated. While I make no claim as to having settled this debate, understanding is gained into the relevance of the T = 0 portion of the effective interactions wherein any effects of T = 0 pairing will reside.;Examining the spectrum in single j shell calculations (j = f7/2 ) provides a first clue that the spectral relevance of this portion of the interaction is often minimal. The most notable thing is the appearance of degenerate states when the T = 0 two-body matrix elements are set to a constant. These degeneracies led to a series of beautiful relations in the angular momentum algebra.;The quest continues in an examination of binding energies and spectra when configuration mixing is allowed. There clues begin to grow concerning the importance of the T = 0 portion of the effective interaction, though we find ourselves with a growing collection of examples where the T = 0 matrix elements need not be present or chosen only as a sensible constant to give respectable physics.;Our epiphany comes when we begin examining the transitions among states constructed with the altered T = 0 effective interactions. Many effects seen to depend on the T = 0 effective interaction can be mimicked by average effects but within the study of certain transitions it is found that the details of the T = 0 part of the effective interaction are crucial to recover what is calculated using the full interaction. This strongly suggests that this region of nuclear structure may be where the question of T = 0 neutron-proton pairing is finally settled.