We review several experimental and theoretical advances that emphasise common
aspects of the study of T=1 and T=0 pairing correlations in nuclei. We first
discuss several empirical evidences of the special role played by the T=1
pairing interaction. In particular, we show the peculiar features of the
nuclear pairing interaction in the low density regime, and possible outcomes
such as the BCS-BEC crossover in nuclear matter and, in an analogous way, in
loosely bound nuclei. We then move to the competition between T=1 and T=0
pairing correlations. The effect of such competition on the low-lying spectra
is studied in N=Z odd-odd nuclei by using a three-body model; it is shown that
the inversion of the 0+ and 1+ states near the ground state, and the strong
magnetic dipole transitions between them, can be considered as a clear
manifestation of strong T=0 pairing correlations in these nuclei. The effect of
T=0 pairing correlations is also quite evident if one studies charge-changing
transitions. The Gamow-Teller (GT) states in N=Z+2 nuclei are studied here by
using self-consistent HFB+QRPA calculations in which the T=0 pairing
interaction is taken into account. Strong GT states are found, near the ground
state of daughter nuclei; these are compared with available experimental data
from charge-exchange reactions, and such comparison can pinpoint the value of
the strength of the T=0 interaction. Pair transfer reactions are eventually
discussed: while two-neutron transfer has been long proposed as a tool to
measure the T=1 superfluidity in the nuclear ground states, the study of
deuteron transfer is still in its infancy, despite its potential interest in
revealing effects coming from both T=1 and T=0 interactions.Comment: Paper submitted to Physica Scripta for inclusion in the Focus Issue
entitled "Focus Issue on Nuclear Structure: Celebrating the 75 Nobel Prize"
(by A. Bohr and B.R. Mottelson). arXiv admin note: text overlap with
arXiv:nucl-th/0512021 by other author
