Nima Arkani-Hamed is championing a campaign to build the world’s largest particle collider, even as he pursues a new vision of the laws of nature.
But if the universe is unnatural and fine-tuned for life, the lucky outcome of a cosmic roulette wheel, then it stands to reason that a vast and diverse “multiverse” of universes must exist beyond our reach — the lifeless products of less serendipitous spins. This multiverse renders our universe impossible to fully understand on its own terms.
Two years ago, he agreed to become the inaugural director of the new Center for Future High Energy Physics in Beijing. He has since visited China 18 times, campaigning for the construction of a machine of unprecedented scale: a circular particle collider up to 60 miles in circumference, or nearly four times as big around as Europe’s Large Hadron Collider (LHC). Nicknamed the “Great Collider,” and estimated to cost roughly $10 billion over 30 years, it would succeed the LHC as the new center of the physics universe. According to Arkani-Hamed and those who agree with him, this 100-trillion-electron-volt (TeV) collider would slam subatomic particles together hard enough to either find the particles that the LHC could not muster or rule them out, rescuing or killing the naturalness principle and propelling physicists toward one of two radically different pictures: that of a knowable universe, or an unknowable multiverse.
Whether a 100-TeV collider materializes or not, Arkani-Hamed’s legacy may rest on a different and potentially more important campaign. Even as he chases the question of whether the properties of the universe are natural, he is also seeking to discover what gives rise to space and time in the first place. As radical as it sounds, many physicists now think that the spatiotemporal dimensions we seem to move around in are not fundamental, but rather emerge from a deeper, truer description of reality. And in 2013, an unexpected discovery by Arkani-Hamed and his student Jaroslav Trnka offered a possible clue to what the underlying laws of nature might look like.
They uncovered a multifaceted geometric object whose volume encodes the outcomes of particle collisions — beastly numbers to calculate with traditional methods. The discovery suggested that the usual picture of particles interacting in space and time is obscuring something far simpler: the timeless logic of intersecting lines and planes. Although the “amplituhedron” (as Arkani-Hamed and Trnka dubbed their object) initially described a simplified version of particle physics, researchers are now working to extend its geometry to describe more realistic particle interactions and forces, including gravity. “It looks like we are going to be able to go very far,” said Zvi Bern, a leader in this research discipline at the University of California, Los Angeles. Arkani-Hamed’s own research is proceeding apace, and he freely speculates about where it will lead.
He believes that the interchangeability of points and lines in the geometry of the amplituhedron may be the origin of a mysterious mathematical dualitybetween particles and strings, the basic building blocks of nature in string theory. And particle interactions are just “the baby version of the problem,” he said. His ultimate goal is to describe the entire cosmological history of the universe as a mathematical object. In unpublished work, he has begun finding patterns in cosmological correlations — the likelihood, for instance, that if two red stars lie 20 kiloparsecs apart, a blue star lies 50 kiloparsecs away from them both. These statistical patterns encode the history of the cosmos, like dinosaur bones buried in the sand. And as with particle collisions, he has found that these patterns can be represented as geometric volumes. Ultimately, he said, anywhere from 10 to 500 years from now, the amplituhedron and these cosmological patterns will merge and become part of a single, spectacular mathematical structure that describes the entire past, present and future of everything “in some timeless, autonomous way.”
