Effect of cluster formation on isospin asymmetry in the liquid-gas phase transition region

Nuclear matter within the liquid-gas phase transition region is investigated in a mean-field two-component Fermi-gas model. Following largely analytic considerations, it is shown that: 1) Due to the density dependence of asymmetry energy, some of the neutron excess from the high-density phase could be expelled into the low-density region. 2) Formation of clusters in the gas phase tends to counteract this trend, making the gas phase more liquid-like and reducing the asymmetry in the gas phase. Flow of asymmetry between the spectator and midrapidity region in reactions is discussed and a possible inversion of the flow direction is indicated. (orig.)