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Public Events

Cover story in New Scientist

Science writer Amanda Gefter in her article “Beyond space-time: Welcome to phase space” in the August 2011 issue of New Scientist features my work. She mistakenly credits Smolin for the variable speed of light prediction from curved momentum space and for Born reciprocity, both two decades old in the work of myself and others. And position-momentum phase space is of course not new either! But she does a fine job explaining the science and has three paragraphs about my own work following a telephone interview:

“Work by Shahn Majid, a mathematical physicist at Queen Mary University of London, might hold some clues. In the 1990s, he showed that curved momentum space is equivalent to what's known as a noncommutative space-time. In familiar space-time, coordinates commute - that is, if we want to reach the point with coordinates (x,y), it doesn't matter whether we take x steps to the right and then y steps forward, or if we travel y steps forward followed by x steps to the right. But mathematicians can construct space-times in which this order no longer holds, leaving space-time with an inherent fuzziness.

In a sense, such fuzziness is exactly what you might expect once quantum effects take hold. What makes quantum mechanics different from ordinary mechanics is Heisenberg's uncertainty principle: when you fix a particle's momentum - by measuring it, for example - then its position becomes completely uncertain, and vice versa. The order in which you measure position and momentum determines their values; in other words, these properties do not commute. This, Majid says, implies that curved momentum space is just quantum space-time in another guise.

What's more, Majid suspects that this relationship between curvature and quantum uncertainty works two ways: the curvature of space-time - a manifestation of gravity in Einstein's relativity - implies that momentum space is also quantum. Smolin and colleagues' model does not yet include gravity, but once it does, Majid says, observers will not agree on measurements in momentum space either. So if both space-time and momentum space are relative, where does objective reality lie? What is the true fabric of reality?”

Read the full article here.

Monday, 8 August 2011