David H. Lyth helped establish when large-scale cosmological curvature is conserved. With David Wands, Karim A. Malik and Andrew R. Liddle, he showed that negligible non-adiabatic pressure perturbations preserve the uniform-density curvature perturbation when spatial-gradient effects are negligible.[ref]
A new approach to the evolution of cosmological perturbations on large scales by David Wands and others. Abstract and sections II–III: conservation derived from local energy conservation
The result specifies when primordial fluctuations can be carried forward without solving every intervening gravitational detail.
Articles by others on the same topic
David H. Lyth is a notable theoretical physicist known for his work in cosmology, particularly in the fields of inflationary theory and the physics of the early universe. He has made significant contributions to the understanding of how the universe expanded and cooled after the Big Bang, and his research often focuses on the implications of cosmic inflation for the formation of large-scale structures in the universe.