Several investigations will be carried out with the common aim of confronting current ideas in theoretical physics and physical cosmology with observations. *Theoretical studies will be made of gravitational lensing effects of cosmic strings. These studies will be used to implement a systematic search for cosmic string lens candidates in a digital sky survey database. Candidate systems will then be submitted to a battery of additional observational screenings. *Theoretical investigation will be made of line emission and line profiles in models of high-redshift clouds producing absorption lines in Quasi-Stellar Object (QSO) spectra. An observational search for their line emission will be made and used to put limits on the high-redshift Ultraviolet (UV) background. *Models will be made of various sources of small-angle anisotropy in the microwave background and applied to recent detections at the Very Large Array (VLA). New observations at a higher radio frequency will be made at the VLA to distinguish between these models. *Theoretical models will be studied of the effect of inhomogeneities from cosmic phase transitions on cosmic nucleosynthesis. A critical evaluation will be made of the range of cosmic baryon densities compatible with observations.
