Why Anthropic Reasoning Cannot Predict Λ
Abstract
We revisit anthropic arguments purporting to explain the measured value of the cosmological constant. We argue that different ways of assigning probabilities to candidate universes lead to totally different anthropic predictions. As an explicit example, we show that weighting different universes by the total number of possible observations leads to an extremely small probability for observing a value of Λ equal to or greater than what we now measure. We conclude that anthropic reasoning within the framework of probability as frequency is illdefined and that in the absence of a fundamental motivation for selecting one weighting scheme over another the anthropic principle cannot be used to explain the value of Λ, nor, likely, any other physical parameters.
 Publication:

Physical Review Letters
 Pub Date:
 November 2006
 DOI:
 10.1103/PhysRevLett.97.201301
 arXiv:
 arXiv:astroph/0607227
 Bibcode:
 2006PhRvL..97t1301S
 Keywords:

 98.80.k;
 Cosmology;
 Astrophysics;
 High Energy Physics  Theory
 EPrint:
 4 pages, 1 figure. Discussion slighlty expanded, refs added, conclusions unchanged. Matches published version