A.-M. M. Abdel-Rahman
A.-M. M. Abdel-Rahman | |
|---|---|
| Known for | Decaying-vacuum and variable cosmological constant cosmology |
| Scientific career | |
| Fields | Cosmology, theoretical physics |
| Institutions | University of Khartoum |
A.-M. M. Abdel-Rahman is a Sudanese theoretical physicist and cosmologist associated with the University of Khartoum, known for developing alternative cosmological models in which the cosmological term (vacuum energy) varies with the expansion of the universe. He is listed in The Worldwide List of Dissident Scientists.
Work
Abdel-Rahman is known for work on "decaying-vacuum" cosmologies, in which the cosmological constant is treated as a quantity that changes over cosmic time rather than as a fixed constant. In a 1992 paper, "Singularity-free decaying-vacuum cosmologies" (Physical Review D 45, 3497), he built on the critical-density model of Özer and Taha and the Chen–Wu ansatz of a cosmological term varying with the scale factor, describing an ever-expanding closed universe in which standard-model nucleosynthesis is preserved while avoiding the initial singularity.
He subsequently extended this line of research to models coupling matter and dark energy. In "Flat Cosmology with Coupled Matter and Dark Energy" (The Astronomical Journal 134, 1391, 2007), written with Ihab F. Riad, he examined a spatially flat cosmology motivated by the observational evidence for an exotic cosmic component of negative pressure (dark energy).
These variable-cosmological-constant and coupled-dark-energy models lie outside the standard constant-Λ (Lambda-CDM) framework and are presented by Abdel-Rahman as alternatives to it.