  We present a theoretical study of the properties of the a1(1260) axial-vector
resonance in a cold nuclear medium. In the vacuum, the a1(1260) resonance is
generated dynamically from the interactions of a pseudoscalar and vector meson
(rho pi and K barK*) in a coupled channel chiral unitary approach. Medium
effects are implemented through the modification of the rho and pi propagators
at finite nuclear density from well established microscopic many-body
calculations. The in-medium pion spectral function accounts for the coupling to
N-hole and Delta-hole excitations including short range correlations, whereas
the in-medium rho incorporates modifications of its virtual pion cloud as well
as direct resonance-hole excitations. The resulting in-medium a1(1260) exhibits
significant broadening with increasing density as reflected in the rho pi
scattering amplitude. The possible relation of our results with partial
restoration of chiral symmetry in nuclear matter is discussed in terms of
in-medium Weinberg sum rules.
