The Geometric Structure That Is Changing Notions of Reality

In Brief

Researchers have characterized a geometric structure, the amplituhedron, that might redefine the essence of space-time — and provide a quantum theory of gravity in the process.

Quantum Confusion

In the 1980s, the US was constructing the Texas Superconducting Super Collider. It was designed to collide protons together so that scientists could study how gluons, which hold the quarks in protons together, interact. But at the time, gluons and their interactions were so complex that understanding them seemed impossible — especially since calculating gluon interaction outcomes involved hundreds of Richard Feynman diagrams and pages of algebra.

In 1986, scientists used supercomputers and Feynman diagrams to calculate the likelihoods of various outcomes of six gluon interactions. They then made an educated guess and posited a one-line formula to replace the more than 200 Feynman diagrams and countless lines of algebra — and their single equation was correct. There was just one problem: they didn’t know why.

Finally, in 2005, a new research team derived the guesswork equation for that same six-gluon interaction, and this time they had a solid guess about what their method (the BCFW method, named after the researchers’ last names) could mean. The basic idea was that the central objects of the theory were rays of light, twistors, rather than particles, and the various terms of the method could be interpreted as volumes of tetrahedrons in twistor space.

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