IL NUOVO CIMENTO VOL. 104 A, N. 9 Settembre 1991 Possible Soft-Core Effect in Heavy-Ion Collisions(*). J. J. MOLITORIS Department of Physics, Muhlenberg College - Alle~town, PA 18104 USA i. BONASERA Dipartimento di Fisica and INFN, Universita di Cata~fia Corso Italia 57, 1-95129 Catania (ricevuto il 6 Agosto 1990; approvato il 29 Gennaio 1991) Summary. -- We study the nuclear equation of state by simulating Nb + Nb heavy-ion collisions from 100 to 1000 MeV/nucleon and solving the Liouville equation with a classical interaction. Sensitivity to the nuclear equation of state is investigated by changing the short-range input nuclear force. A stiffer short-range potential is shown to result in greater transverse momentum transfer and collective flow angle. We provide a qualitative explanation of recent LBL/GSI plastic ball data, which show a saturation of the flow, in terms of the classical many-body model with internucleon potential V(r= 0) finite. PACS 25.70.Np - Fragmentation and relativistic collisions. A classical or semi-classical description of heavy-ion collisions is considered a reasonable approach for intermediate energies (100 + 1000) MeV/nucleon because of the high degree of thermal excitation that tends to smear out nuclear structure and the quantum-mechanical features of the system[I]. The models that describe the nucleon motion in terms of classical trajectories and forces are called classical equations of motion (CEOM) models[I-4]. The CEOM model of heavy-ion physics solves Newton's or Hamilton's equations of motion for the A = Ap + AT interacting nucleons in the projectile and target. This is thus a theory for the full nonequilibrium classical situation. The CEOM is more fundamental than a kinetic equation in that it solves the A-body Liouville equation: (1) 3~/3t= {H,~}, where H=H(rl,...,ra,pl,...,pa) is the many-body Hamiltonian and ,:= = :(r~ .... , ra, p~ .... , Pa) is the A-body distribution function. For a local interaction, this equation is equivalent to the Newtonian equations Fi = dpi/dt = -dU/dri where the (*) The authors of this paper have agreed to not receive the proofs for correction. 1355