SPACE-TIME PROBES OF LARGE-SCALE STRUCTURE EVOLUTION

The time evolution of large structures is discussed as an emerging area in observational cosmology. The richness and complexity of the research arise because astronomers still have a poor understanding of the relationship between the observed structures and the bias, formation, and evolution of the tracers themselves, such as gas, dark matter, galaxies, and active galactic nuclei. The choices of tracers, wavelength regime, analysis techniques, and sampling strategies to tackle the problem have a large diversity that will lead to an explosive growth of new data. Complementing these observations will be a new generation of hydrodynamic models of structure information; the inclusion of gas is likely to be the key component needed to unravel the intimate link between the mass fluctuation spectrum of the universe and large scale structure of the various tracers at different epochs. Several major surveys focused on the spatial distribution of distant matter are already underway; they should yield important discoveries by the end of this millennium.