  Abstrtact: Random matrix ensembles defined by a mean-field one-body plus a
chaos generating random two-body interaction (called embedded ensembles of
(1+2)-body interactions) predict for wavefunctions, in the chaotic domain, an
essentially one parameter Gaussian forms for the energy dependence of the
number of principal components NPC and the localization length ${\boldmath
$l$}_H$ (defined by information entropy), which are two important measures of
chaos in finite interacting many particle systems. Numerical embedded ensemble
calculations and nuclear shell model results, for NPC and ${\boldmath $l$}_H$,
are compared with the theory. These analysis clearly point out that for
realistic finite interacting many particle systems, in the chaotic domain,
wavefunction structure is given by (1+2)-body embedded random matrix ensembles.
