Joseph Polchinski

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Joseph Polchinski
Joseph Polchinski.jpg
Joe Polchinski in Santa Barbara
Born (1954-05-16) May 16, 1954 (age 63)
White Plains, New York
Known for D-branes[1]
Polchinski's paradox
Everett phone
Awards Dannie Heineman Prize for Mathematical Physics (2007)
Dirac Medal (2008)
Physics Frontier Prize (2013)
Fundamental Physics Prize (2017)
Scientific career
Institutions University of California, Santa Barbara
Doctoral advisor Stanley Mandelstam

Joseph Polchinski (born May 16, 1954) is an American theoretical physicist and string theorist.


Polchinski graduated from Canyon del Oro High School in Tucson, Arizona in 1971, obtained his B.S. degree from Caltech in 1975, and his Ph.D. from the University of California, Berkeley in 1980 under the supervision of Stanley Mandelstam. After postdoctoral positions at SLAC (1980–82) and Harvard (1982–84) he was professor at the University of Texas at Austin from 1984 to 1992. Since 1992 he has been professor in the Physics Department of the University of California, Santa Barbara and a permanent member of the Kavli Institute for Theoretical Physics there.[2]

Polchinski is the author of the two-volume textbook String Theory, published in 1998. Among his contributions to theoretical physics, D-branes are the best known. In 2008 he won the Dirac Medal for his work in superstring theory.[3] He won the 2017 Fundamental Physics Prize.[4]

He recovered from brain cancer and he cannot say if he will be able to do research again.[5]


Polchinski's paradox[edit]

In an unpublished communication to Kip Thorne circa 1990, commenting on the Novikov self-consistency principle (in relation to sending objects or people through a traversable wormhole into the past, and the time paradoxes that could result), Polchinski raised a potentially paradoxical situation involving a billiard ball sent through a wormhole which sends it back in time. In this scenario, the ball is fired into a wormhole at an angle such that, if it continues along that path, it will exit the wormhole in the past at just the right angle to collide with its earlier self, thereby knocking it off course and preventing it from entering the wormhole in the first place. Thorne dubbed this problem "Polchinski's paradox" in 1994.[6] Later students of the whimsical problem came up with solutions which managed to avoid any inconsistencies, by having the ball emerge from the future at a different angle than the one used to generate the paradox, and deliver its younger self a glancing blow instead of knocking it completely away from the wormhole, a blow which changes its trajectory in just the right way so that it will travel back in time with the angle required to deliver its younger self this glancing blow.[6]

2012 paper on black holes[edit]

In July 2012, Polchinski, together with two of his students — Ahmed Almheiri and Jamie Sully — and fellow string theorist Donald Marolf at the University of California, Santa Barbara (UCSB), published a paper[7] whose calculations about black hole radiation seemed to suggest that either general relativity's equivalence principle is wrong, or else a key tenet of quantum mechanics is incorrect.[8]


  • Polchinski, Joseph (1998a), String Theory Vol. I: An Introduction to the Bosonic String, Cambridge University Press, ISBN 0-521-63303-6 
  • Polchinski, Joseph (1998b), String Theory Vol. II: Superstring Theory and Beyond, Cambridge University Press, ISBN 0-521-63304-4 


  1. ^ Polchinski, J. (1995). "Dirichlet branes and Ramond-Ramond charges." Physical Review D, 50(10), R6041–R6045.
  2. ^ Archived 2007-04-17 at the Wayback Machine.
  3. ^
  4. ^ Leachman, Shelly (December 5, 2016). "Another Major Breakthrough". University of California, Santa Barbara. Retrieved December 5, 2016. 
  5. ^ Polchinski, Joseph (August 31, 2017). "Memories of a Theoretical Physicist". arxiv. Retrieved August 31, 2017. 
  6. ^ a b Thorne, Kip S. (1994). Black Holes and Time Warps. W. W. Norton. pp. 510–513. ISBN 0-393-31276-3. 
  7. ^ Almheiri, Ahmed; Marolf, Donald; Polchinski, Joseph; Sully, James (11 February 2013). "Black holes: complementarity or firewalls?". Journal of High Energy Physics. 2013 (2). arXiv:1207.3123Freely accessible. Bibcode:2013JHEP...02..062A. doi:10.1007/JHEP02(2013)062. 
  8. ^ "Astrophysics: Fire in the hole!"

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