Niels Grønbech-Jensen was appointed Systemwide Faculty Executive Director of the California State Summer School for Mathematics and Science (COSMOS) program in June 2015, after serving in the role as interim for eight months. He is a distinguished professor with a dual appointment in mathematics and mechanical and aerospace engineering and has served as a COSMOS instructor since 2004. 

A four-week residential academic enrichment program for high-performing California high school students excelling in STEM fields, COSMOS was legislated into existence in 1998, and had its first student summer activities at two UC campuses in 2000. With a UC decision to locate a coordinating COSMOS office at UC Davis in 2014, Grønbech-Jensen has focused on aligning systemwide policies and procedures, securing funds for supporting admitted students in financial need, and increasing systemwide involvement to more UC campuses, thereby addressing the increasingly large number of academically qualified applications to the program. As of 2024, the program operates on five UC campuses and has an annual enrollment of more than 1,100 students.

Grønbech-Jensen came to the Department of Applied Science at UC Davis in 1999 from the Theoretical Division at Los Alamos National Laboratory, where he had worked on nonlinear dynamical systems with applications to, e.g., superconducting electronics and optical systems, and on molecular dynamics with applications to, e.g., radiation effects in crystalline materials, high-energy chemical materials, and molecular self-assembly. Through a joint faculty appointment with Lawrence Berkeley National Laboratory and a number of department affiliations at UC Davis, Grønbech-Jensen's interests evolved into investigations of how to distinguish quantum phenomena from classical behavior in macroscopic systems. For the past decade, he has developed a significantly improved set of numerical algorithms that produces both efficient and accurate statistical results when conducting simulations of thermodynamic systems. Grønbech-Jensen has worked extensively with colleagues from U.S. National Laboratories as well as international institutions.

Grønbech-Jensen is a Fellow of the American Physical Society, and was educated at the Technical University of Denmark, where he received a Master's of Science in applied mathematical physics and a Ph.D. in condensed matter physics.