A systematic study of energy spectra for light particles emitted at mi
drapidity from Au + Au collisions at E = (0.25-1.15)A GeV reveals a si
gnificant nonthermal component consistent with a collective radial flo
w. This component is evaluated as a function of bombarding energy and
event centrality. Comparisons to quantum molecular dynamics and Boltzm
ann-Uehling-Uhlenbeck models are made for different equations of state
.