The universe from scratch
Abstract
A fascinating and deep question about nature is what one would see if one could probe space and time at smaller and smaller distances. Already the 19th century founders of modern geometry contemplated the possibility that a piece of empty space that looks completely smooth and structureless to the naked eye might have an intricate microstructure at a much smaller scale. Our vastly increased understanding of the physical world acquired during the 20th century has made this a certainty. The laws of quantum theory tell us that looking at spacetime at ever smaller scales requires ever larger energies and, according to Einstein's theory of general relativity, this will alter spacetime itself: it will acquire structure in the form of curvature. What we still lack is a definitive theory of quantum gravity to give us a detailed and quantitative description of the highly curved and quantumfluctuating geometry of spacetime at this socalled Planck scale. This article outlines a particular approach to constructing such a theory, that of Causal Dynamical Triangulations, and its achievements so far in deriving from first principles why spacetime is what it is, from the tiniest realms of the quantum to the largescale structure of the universe.
 Publication:

Contemporary Physics
 Pub Date:
 April 2006
 DOI:
 10.1080/00107510600603344
 arXiv:
 arXiv:hepth/0509010
 Bibcode:
 2006ConPh..47..103A
 Keywords:

 High Energy Physics  Theory;
 General Relativity and Quantum Cosmology;
 High Energy Physics  Lattice
 EPrint:
 31 pages, 5 figures