Two-dimensional Fourier transform spectroscopy, an extension of four-wave mixing (FWM), is able to resolve numerous aspects of many-body effects and higher-order Coulomb interactions that contribute to the ultrafast dynamics of quantum wells and bulk GaAs resonances. Coherent oscillations between heavy-hole and light-hole excitons -or quantum beats -can be unfolded from the exciton populations by Fourier transforming FWM data with respect to two time-axes. Excitation conditions such as pulse

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... ering, polarization, tuning and pulse energy can isolate Feynman pathways and highlight the coherent many-body correlations, including those from biexcitons. In addition, the bulk exciton and continuum states are studied more carefully for their dynamics.