Ann Nelson

We were saddened to hear about the tragic accidental death of theoretical particle physicist and University of Washington Professor Dr. Ann Nelson, who developed theories to explain why particles behave in unpredicted ways and advocated strongly for increased diversity in science.

Photo credit: David Kaplan

Nelson was born in Baton Rouge, Louisiana April 29, 1958 and her family moved to San Francisco Bay Area when she was young. She carried out undergraduate studies at Stanford, where she made an early impact and had the opportunity to spend one summer working at CERN (the European Organization for Nuclear Research in Geneva).

After graduating from Stanford she pursued a Ph.D. from Harvard under the mentorship of Howard Georgi. In 1984, while still a graduate student, she proposed a solution to the “strong CP problem” to account for why particles behave in ways that aren’t predicted by the Standard Model describing the properties of fundamental particles making up the universe. This solution was also independently proposed by Stephen Barr, leading it to be called the Nelson-Barr mechanism.

She went on to propose theories for how the electromagnetic force and the weak force, which were unified in the early universe, split apart, as well as explanations for electroweak symmetry breaking and supersymmetry.

Despite the highly competitive atmosphere of theoretical particle physics, Nelson recognized the value of collaboration and published papers with researchers from all over the world and all levels of “prestige” – though her most frequent co-author was her husband, David Kaplan, whom she met at Stanford.

Though her theoretical masterpieces were highly influential, Nelson’s contributions didn’t start and end in scientific research – she was an avid equal rights activist, especially passionate about increasing diversity in scientific fields including her own, which has been notoriously white-male-dominated. She spoke out against inequality and underrepresentation of demographic groups in science, and worked actively to combat these issues by taking initiatives like teaching physics lecture in Palestine, helping underrepresented students find jobs, and writing a Physics Today article on “Diversity in physics”

Nelson’s many honors include the Guggenheim Fellowship (2004), the American Physical Society’s J.J. Sakurai Prize for Theoretical Particle Physics, and election into the American Academy of Arts and Sciences (AAAS) (2011) and the National Academy of Sciences (NAS) (2012). Nelson died August 4, 2019 from a hiking accident and her loss has been deeply felt.

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