Joseph Gerard Polchinski Jr.[2] (/pəlˈtʃɪnski/; May 16, 1954 – February 2, 2018) was an American theoretical physicist and string theorist.

[7] Polchinski graduated from Canyon del Oro High School in Tucson, Arizona, in 1971.

In an unpublished communication to Kip Thorne circa 1990, commenting on the Novikov self-consistency principle (in relation to sending objects or people through a traversable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.

[11] In July 2012, Polchinski, with two of his students, James Sully and Ahmed Almheiri, and fellow string theorist Donald Marolf at the University of California, Santa Barbara (UCSB), published a paper[12] whose calculations about black hole radiation suggested that either general relativity's equivalence principle is wrong, or else a key tenet of quantum mechanics is incorrect.

In the episode "The Paintball Scattering", Sheldon would choke up and be unable to respond every time anybody asked if the paper on super-symmetry, which he had recently published with his wife, Amy, was derivative of the work of Polchinski.