By F. Adams, G. Laughlin
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Extra info for A Dying Universe - Long-Term Fate of Astrophys. Objects [lg article]
On the other hand, if the very large scale density perturbations have small amplitude (∆ρ/ρ ≪ 1), then the universe can continue to expand for much longer time scales. If the universe is currently open, then large scale density perturbations are essentially frozen out. C. Inflation and the Future of the Universe The inflationary universe scenario was originally invented (Guth, 1981) to solve the horizon problem and the flatness problem faced by standard Big Bang cosmology (see also Albrecht & Steinhardt, 1982; 33 Linde, 1982).
On the other hand, if the vacuum energy density is strictly zero, then future (large) densities perturbations can, in principle, enter our horizon and lead (locally) to a closed universe and hence a big crunch. [C] What is the nature of the dark matter? Of particular importance is the nature of the dark matter that makes up galactic halos. The lifetime of the dark matter particles is also of great interest. [D] What fraction of the stars in a galaxy are evaporated out of the system and what fraction are accreted by the central black hole (or black holes)?
31 V. LONG TERM EVOLUTION OF THE UNIVERSE In spite of the wealth of recent progress in our understanding of cosmology, the future evolution of the universe cannot be unambiguously predicted. In particular, the geometry of the universe as a whole remains unspecified. The universe can be closed (k = +1; Ω > 1), flat (k = 0; Ω = 1), or open (k = −1; Ω < 1). In addition, the contribution of vacuum energy density remains uncertain and can have important implications for the long term evolution of the universe.