  The s, d bosons of the Interacting Boson Model are being derived from the
Shell Model space, through the Elliott or the proxy SU(3) symmetry. A novel
interpretation of the s, d bosons is therefore introduced: each boson results
from the coupling of two harmonic oscillator quanta. Such quanta obey to the
boson statistics and as a result their coupled states satisfy the bosonic
commutators too, without using any approximation. Thus, the mapping of two
harmonic oscillator quanta onto an s or a d boson is accurate. Furthermore,
through this interpretation, it emerges naturally, that the nuclear states of
even-even nuclei can be described solely by spherical tensors of degree L=0, 2,
namely by the s, d bosons of the Interacting Boson Model. Beginning from the
occupancy of the cartesian Shell Model states by protons or neutrons, one may
result to certain U(6) irreps, which inherit some of the fermionic
characteristics from the initial Shell Model space. Practically this means,
that the bosons of the Interacting Boson Model span the whole 6 dimensional
space of the U(6) symmetry. As a result a microscopic justification of the
coherent states emerges from first principles.
