LETTER TO THE EDITOR: On the dimensionality of spacetime
Abstract
Some superstring theories have more than one effective lowenergy limit corresponding to classical spacetimes with different dimensionalities. We argue that all but the (3 + 1)dimensional one might correspond to `dead worlds', devoid of observers, in which case all such ensemble theories would actually predict that we should find ourselves inhabiting a (3 + 1)dimensional spacetime. With more or less than one time dimension, the partial differential equations of nature would lack the hyperbolicity property that enables observers to make predictions. In a space with more than three dimensions, there can be no traditional atoms and perhaps no stable structures. A space with less than three dimensions allows no gravitational force and may be too simple and barren to contain observers.
 Publication:

Classical and Quantum Gravity
 Pub Date:
 April 1997
 DOI:
 10.1088/02649381/14/4/002
 arXiv:
 arXiv:grqc/9702052
 Bibcode:
 1997CQGra..14L..69T
 Keywords:

 General Relativity and Quantum Cosmology;
 High Energy Physics  Phenomenology;
 High Energy Physics  Theory
 EPrint:
 Minor modifications to match published version. 5 pages. Color figures and related links at http://www.sns.ias.edu/~max/dimensions.html (faster from the US), from http://www.mpagarching.mpg.de/~max/dimensions.html (faster from Europe) or from max@ias.edu