I develop theories of the early universe, making a number of successful predictions within the standard dark energy/dark matter cosmology. My group pioneered investigations of theoretical scenarios including cosmic strings, inflationary “bubble” universes and cyclic models. We disproved the Hartle-Hawking proposal for inflationary universes. Additionally, we are developing an alternative, the CPT-invariant universe, which provides the simplest-yet explanation for the cosmic dark matter.