Note to users. If you're seeing this message, it means that your browser cannot find this page's style/presentation instructions -- or possibly that you are using a browser that does not support current Web standards. Find out more about why this message is appearing, and what you can do to make your experience of our site the best it can be.

Site Tools

  • AAAS
  • Subscribe
  • Feedback

Site Search

Search Advanced

Originally published in Science Express on 4 May 2006
Science 26 May 2006:
Vol. 312. no. 5777, pp. 1180 - 1183
DOI: 10.1126/science.1126231
Prev | Table of Contents | Next

Research Articles

Why the Cosmological Constant Is Small and Positive

Paul J. Steinhardt1* and Neil Turok2

Within conventional big bang cosmology, it has proven to be very difficult to understand why today's cosmological constant is so small. In this paper, we show that a cyclic model of the universe can naturally incorporate a dynamical mechanism that automatically relaxes the value of the cosmological constant, including contributions to the vacuum density at all energy scales. Because the relaxation time grows exponentially as the vacuum density decreases, nearly every volume of space spends an overwhelming majority of the time at the stage when the cosmological constant is small and positive, as observed today.

1 Joseph Henry Laboratories, Princeton University, Princeton, NJ 08544, USA.
2 Department of Applied Mathematics and Theoretical Physics (DAMTP), Center for Mathematical Sciences (CMS), Cambridge University, Wilberforce Road, Cambridge, CB3 0WA, UK.

* To whom correspondence should be addressed. E-mail: steinh{at}princeton.edu

Read the Full Text

To Advertise     Find Products

Science. ISSN 0036-8075 (print), 1095-9203 (online)