Atomic nuclei are strongly correlated fermionic systems. This is apparent
from the (experimentally observed) depopulation of single particle orbits
and the redistribution of spectral strength due to coupling to collective
excitation modes. Such features are now fairly well understood for closed
shell stable isotopes.
However, they appear to evolve in non trivial ways moving toward the
driplines, e.g., leading to the rearrangement of shell closures and exotic
resonances.
The talk will discuss recent developments in calculations of the nuclear
spectral function, based on  the many-body Green's functions method, which
will allow to tackle the above problems.
Some applications to both stable and exotic nuclei will be discussed.