# Lydia Bieri

Lydia Rosina Bieri (born 1972) is a Swiss-American applied mathematician, geometric analyst, mathematical physicist, cosmologist, and historian of science whose research concerns general relativity, gravity waves, and gravitational memory effects. She is a professor of mathematics and director of the Michigan Center for Applied and Interdisciplinary Mathematics at the University of Michigan.

## Early Life

Bieri originally from Sempach, in Switzerland, with her parents and younger brother. Always around nature, Bieri grew accustomed to inquiry and, with the guidance of her parents, learned early on to question others beliefs to further structure her own. Her journey with mathematics and physics started when she was young reading about astronomy.

## Education and career

Bieri studied mathematics at ETH Zurich, earning a diploma (the equivalent of a master's degree) in 2001. She completed a doctorate (Dr. sc.) at ETH Zurich in 2007, with the support of a Swiss National Funds Fellowship. Her dissertation, An Extension of the Stability Theorem of the Minkowski Space in General Relativity, was supervised by Demetrios Christodoulou, and jointly promoted by Michael Struwe.
After postdoctoral research as a Benjamin Peirce Fellow in mathematics at Harvard University from 2007 to 2010, Bieri became an assistant professor of mathematics at the University of Michigan in 2010. She became associate professor in 2015, director of the Michigan Center for Applied and Interdisciplinary Mathematics in 2019, and full professor in 2021.

## Books

With Harry Nussbaumer of ETH Zurich, Bieri is the coauthor of a general-audience book on cosmology and its history, Discovering the Expanding Universe (Cambridge University Press, 2009), She is also the coauthor of a research monograph with Nina Zipser, Extensions of the Stability Theorem of the Minkowski Space in General Relativity (AMS/IP Studies in Advanced Mathematics, American Mathematical Society, 2009).

## Research

Lydia Bieri has made profound contributions to understanding the mathematical structures and dynamics of the universe, with a primary focus on general relativity. Her research delves into the intricate interplay of geometry and physics as encapsulated in Einstein's equations, which describe the geometry of spacetime and the phenomenon of gravitation—the fundamental laws governing the universe. Bieri develops advanced geometric-analytic frameworks that not only solve significant questions in physics but also have independent mathematical implications, extending their application to diverse fields such as economics and biology.
A key avenue of her work explores gravitational waves, ripples in spacetime resulting from cosmic events like black hole mergers, neutron star collisions, or supernovae. Since the groundbreaking detection of gravitational waves by the Advanced LIGO experiment in 2015, Bieri's investigations have illuminated how these phenomena provide unprecedented insights into otherwise inaccessible regions of the universe. Her studies encompass the memory effect of gravitational waves—lasting imprints on the curvature of spacetime—linking rigorous mathematical theory to experimental findings.
Additionally, Bieri's research addresses foundational questions in astrophysics and cosmology, including the formation and stability of black holes and galaxies, as well as the profound mysteries connecting large-scale cosmological structures with quantum phenomena. These efforts aim to bridge the gap between general relativity and quantum field theory, tackling one of modern physics' greatest challenges: understanding the relationship between dark energy and vacuum energy.
Through her work on nonlinear partial differential equations and geometric analysis, Bieri continues to unravel the complex synergy between mathematics and physics, advancing knowledge of the universe while opening new paths for interdisciplinary applications.

## Recognition

Bieri won an NSF CAREER Award in 2013 and was named a Simons Fellow in Mathematics in 2018. She was named a Fellow of the American Physical Society (APS) in 2021, after a nomination from the APS Division of Gravitational Physics, "for fundamental results on the global existence of solutions of the Einstein field equations, and many contributions to the understanding of gravitational wave memory". She was named to the 2023 class of Fellows of the American Mathematical Society, "for contributions to mathematical general relativity and geometric analysis".