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Light May Arise From Tiny Relativity Violations

Light may arise from tiny relativity violations, according to a new theory. Speaking most recently at last month's American Physical Society meeting of the Division of Atomic, Molecular, and Optical Physics in Nebraska, Alan Kostelecky of Indiana University (812 855-1485, KOSTELEC@INDIANA.EDU) described how light might exist as a result of breaking an assumption of relativity theory known as Lorentz symmetry. In Lorentz symmetry, the laws of physics stay the same even when you change the orientation of a physical system (such as a barbell-shaped molecule) or alter its velocity.

According to special relativity, the speed of light is the same in every direction, a notion that current experiments verify to a few parts in 10^16. However, if physicists find variations in the speed of light with direction, this would provide evidence for broken Lorentz symmetry, which would radically revise notions of the universe. Broken Lorentz symmetry would give spacetime a preferred direction. In its simplest form, broken Lorentz symmetry could be visualized as a field of vectors (arrows) existing everywhere in the universe.

In such a picture, objects might behave slightly differently depending upon their orientation with respect to the vectors. In a recent paper, published in Physical Review D (Bluhm and Kostelecky, Physical Review D, 71, 065008, published 22 March 2005; text at www.aip.org/physnews/select), the authors propose that the very existence of light is made possible through a vector field arising from broken Lorentz symmetry. In this picture, light is a shimmering of the vector field analogous to a wave blowing through a field of grain

The researchers have shown that this picture would hold in empty space as well as in the presence of gravity (curved spacetime) which is often ignored in conventional theories of light. This theory is in contrast to the conventional view of light, which arises in a space without a preferred direction and as a result of underlying symmetries in particles and force fields. Kostelecky says that the new theory can be tested by looking for minute changes in the way light interacts with matter as the earth rotates (and changes its orientation with respect to the putative vector field).

In addition, Kostelecky says that neutrino oscillations might arise from interactions between neutrinos and the background vector field, as opposed to the conventional explanation, which invokes neutrino mass as the explanation for the oscillations. Experimentalist Ron Walsworth of Harvard-Smithsonian comments that the nice thing about Kostelecky's work is that he proposes detailed experiments to test his theories; and that the results of such experiments, no matter how they turn out, promise to deepen our understanding of physics. (For more information, see article by Kostelecky in the Scientific American, September 2004; as well as Indiana University Press Release, March 21).