Why the Cosmological Constant Is Small and Positive in Science 312 No. 5777 pp. 1180 - 1183, May 26, 2006

New York: AAAS, 2006. 1st Edition. FIRST EDITION IN ORIGINAL WRAPS OF STEINHARDT & TUROK'S EXPLANATION OF HOW THEIR 2002 CYCLIC THEORY OF THE UNIVERSE CAN RESOLVE THE COSMOLOGICAL CONSTANT PROBLEM. Steinhardt and Turok's 2002 cyclic universe theory is a model of cosmic evolution according to which the universe undergoes endless cycles of expansion and cooling, each beginning with a "big bang" and ending in a "big crunch" (Steinhardt, Cyclic Universe Theory, 2009). In the paper offered here, the 2006 paper, the two show "how the cyclic model could naturally incorporate a mechanism for relaxing the cosmological constant to very small values, consistent with current observations" (WP). We separately offer a second copy of both the 2002 paper and the 2002 paper together with the 2006.

The model has also been known as the ekpyrotic cyclic universe theory. Paul Joseph Steinhart is an American theoretical physicist and cosmologist, currently the Albert Einstein Professor in Science at Princeton University. Beginning in 2001 and working with the South African physicist Neil Geoffrey Turok, Steinhardt and Turok put forth the ekpyrotic theory which, in essence, envisions a big bounce rather than a big bang. "According to this model, the current expanding universe emerges from a bounce that occurred 13.7 billion years ago and that is a result of the preceding (contracting) universe. The smoothing and flattening of the universe and the generation of density variations occur during the phase of slow contraction before the bounce and remain after the bounce" (Wikipedia). In their own words: "The Cyclic Model attempts to resolve the homogeneity, isotropy, and flatness problems and generate a nearly scale-invariant spectrum of fluctuations during a period of slow contraction that precedes a bounce to an expanding phase. Here we describe at a conceptual level the recent developments that have greatly simplified our understanding of the contraction phase and the Cyclic Model overall (Steinhardt & Turok, 24 May 2002). CONDITION & DETAILS: New York: AAAS. Complete 1st edition in original wraps, complete. 8vo. Bright and clean inside and out. Near fine condition.