Fermi National Laboratory

Volume 25  |  Friday, April 19, 2002  |  Number 7
In This Issue  |  FermiNews Main Page

The Larger View
Fermilab postdoc Nicole Bell explores an award-winning pathway

by Mike Perricone

To Nicole Bell, physics is the most fundamental of the sciences. We're trying to answer really big questions. Gaining a larger view of the world is always challenging, though not always as suspenseful as the first time you sit in a car with the steering wheel on the wrong side and try to drive on the wrong side of the road.

“My passenger kept shouting, ‘You’re too close! Watch out for the parked cars!’” said Nicole Bell, accustomed to driving on the left, with the steering wheel on the right, in her native Australia. “But I didn’t hit anything, and pretty soon it seemed like the normal thing to do.”

Having met the driving challenge, Bell quickly settled into her daily routine as a postdoc at Fermilab: arriving early from her apartment in nearby Naperville, reading research papers, doing calculations, going to talks, working late, working weekends like other postdocs around the lab, trying to match the months to the correct seasons in the northern hemisphere, winning awards…

The first award came in February, less than six months after Bell joined Fermilab’s Theoretical Astrophysics Group, her first research appointment after receiving her Ph.D. from the University of Melbourne in Australia. She received the 2001 Bragg Gold Medal in Physics, awarded by the Australian Institute of Physics for the best physics Ph.D. thesis (“Neutrino Oscillations and the Early Universe”) at an Australian University.

In March, Bell was among the second-place winners in the Young Researchers Competition, sponsored by the John Templeton Foundation, during the “Science and Ultimate Reality” symposium held March 15-18 near Princeton, New Jersey. The symposium was held to celebrate the 90th birthday of physicist John Archibald Wheeler.

“Wheeler worked with Niels Bohr, his students included Richard Feynman, he gave black holes their name, and that’s the short list,” said Bell. “He had a hand in so many things, from general relativity to quantum mechanics. There were many famous people giving talks throughout the conference. It was thrilling to give a talk at a conference attended by people such as Wheeler, Freeman Dyson, Wojciech Zurek, Juan Maldacena, Andrei Linde and Lisa Randall.”

Bell led off the presentations by the 15 finalists in the international competition for researchers born during or after January 1970 (at 26, she was one of the youngest of the finalists). Her talk (“Coherence, Decoherence and Oscillating Neutrinos—From Quantum Zeno to Getting in Sync”) was based on work begun during her Ph.D. at Melbourne with advisor Ray Volkas and collaborator Ray Sawyer. She explored the role of neutrinos in the early universe—under conditions where the matter density is so high that collisions of neutrinos with other particles disturb (“decohere”) neutrino oscillations. The link to “ultimate reality:” Decoherence is the process where quantum systems lose their “quantum-ness.” It plays a fundamental role in the emergence of classical reality from an underlying quantum world.

“The Quantum Zeno Effect is the freezing of the evolution of a system that undergoes rapid system-environment interactions,” she explained. “It’s a ‘watched pot never boils’ effect. In the early universe, the collisions of the neutrinos can lead to this sort of freezing—the neutrino oscillations are inhibited. The Zeno effect arises when the two neutrino flavors interact with the environment differently—for example, active flavors as opposed to sterile flavors. In a sense, the environment ‘measures’ the neutrino flavor.”

But then it all changed.

“If the environment is ‘blind’ to the flavor of the neutrino, this Zeno freezing does not occur,” Bell continued. “However, there is an analogous effect: synchronization (or ‘motional narrowing’). Usually, neutrinos of different energies oscillate at different frequencies, but rapid ‘flavor blind’ collisions can cause all energy modes to oscillate in a synchronized fashion. An example would be mu and tau neutrino oscillations in an environment of electrons.”

Bell was one of seven second-place finishers, each receiving awards of $5,000; two first-place finishers each won $7,500. The symposium received extensive coverage in The New York Times, among other major news and science publications.

“This award is a well-deserved recognition of Nicole’s excellent work on novel aspects of neutrino oscillations in many-particle systems,” said John Beacom, Fermilab theoretical astrophysicist and David Schramm Research Fellow, who had encouraged her to enter the competition. “Her work demonstrates the exciting interplay that connects ongoing results from neutrino oscillation experiments to important questions about the early universe.”

Bell, Beacom and Fermilab postdoc Kev Abazajian recently completed a paper on the role of neutrino oscillations in setting a limit on the lepton number of the universe.

“This is vital in using Big Bang Nucleosynthesis [origin of the first chemical elements] to constrain neutrino properties, and vice versa,” she explained.

Bell applied for the postdoctoral position at Fermilab because she was drawn by the access to both cosmology and particle physics and the chance to work with a wide range of researchers.

“To me, physics is the most fundamental of the sciences,” she said. “We’re trying to answer really big questions.”

They’re the kinds of questions that lead to a larger view of the world.

On the web:

Nicole Bell's home page
Fermilab Theoretical Astrophysics
Science and Ultimate Reality
Bragg Gold Medal, Australian Institute of Physics

last modified 4/19/2002   email Fermilab