Spin isovector responses in finite nuclei.

We present a unified investigation of the spin-isospin responses of a finite nucleus in both the spin-transverse (σ→×q→) and spin-longitudinal (σ→⋅q→) channels, utilizing the formalism of the polarization propagator, Πμν. The independent particle transverse response (evaluated in a harmonic oscillator basis) fails to reproduce the recent data from deep inelastic (e,e’) scattering, thus pointing to the existence of collective effects. As a preliminary step toward the solution of the random-phase-approximation equations for Πμν, we explore in detail the mixed-coupling propagator, which may produce significant differences between the collective response of infinite nuclear matter and the one of a finite system.