Joseph Polchinski was a preeminent American theoretical physicist whose transformative contributions reshaped modern string theory and quantum gravity. Born in White Plains, New York on May 16, 1954, he earned his BS in Physics from the California Institute of Technology in 1975 and completed his PhD at UC Berkeley in 1980 under Stanley Mandelstam. Following postdoctoral positions at the Stanford Linear Accelerator Center and Harvard University, he joined the faculty at the University of Texas at Austin in 1984 before moving to the University of California, Santa Barbara in 1992. At UCSB, he served as a Professor of Physics and Permanent Member of the Kavli Institute for Theoretical Physics until becoming Professor Emeritus in 2017, establishing himself as one of the most influential theoretical physicists of his generation until his passing on February 2, 2018.
Polchinski's most celebrated contribution was his groundbreaking discovery of D-branes, extended structures that fundamentally transformed string theory and became central to its mathematical and physical framework after his pivotal 1995 work. His elegant reformulation of renormalization theory provided a more mathematically coherent framework that advanced quantum field theory, while his work on the string landscape opened new avenues for understanding the cosmological constant problem. Additionally, his proposal of the black hole firewall paradox challenged longstanding assumptions about black hole physics and created a major research direction that continues to provoke intense debate about the nature of quantum gravity. Polchinski's two-volume textbook on string theory became the definitive graduate-level reference, educating generations of theoretical physicists through its exceptionally clear exposition of complex concepts.
Beyond his seminal research contributions, Polchinski deeply influenced theoretical physics through his exceptional clarity of thought and willingness to fundamentally reassess conventional wisdom, as evidenced by his late-career memoir 'Memories of a Theoretical Physicist' which provided profound insights into the development of string theory. His numerous prestigious honors, including the Dirac Medal, the Dannie Heineman Prize, and election to the National Academy of Sciences, reflected the scientific community's recognition of his transformative impact on theoretical physics. Following his diagnosis with brain cancer, Polchinski devoted his final years to documenting his scientific journey and perspective, leaving behind a rich intellectual legacy that continues to guide researchers in quantum gravity and related fields. His passing elicited an extraordinary outpouring of respect from colleagues worldwide, testifying to his standing as a theoretical physicist's theoretical physicist whose insights permanently altered humanity's understanding of the fundamental nature of reality.
