James Hartle

James Burkett Hartle (August 17, 1939 – May 17, 2023) was an American theoretical physicist. He joined the faculty of the University of California, Santa Barbara in 1966, and was a member of the external faculty of the Santa Fe Institute. Hartle is known for his work in general relativity, astrophysics, and interpretation of quantum mechanics.

Early life
Hartle was born on August 17, 1939, in Baltimore to Anna Elizabeth Burkett and Charles James Hartle. He began as an engineering major upon entering Princeton, but switched to physics due to the influence of John Wheeler.

Hartle completed his AB at Princeton University in 1960 and his Ph.D. in particle physics under Murray Gell-Mann in 1964.

Work
In collaboration with Gell-Mann and others, Hartle developed an alternative to the standard Copenhagen interpretation, more general and appropriate to quantum cosmology, based on consistent histories.

With Dieter Brill in 1964, he discovered the Brill–Hartle geon, an approximate solution realizing Wheeler's suggestion of a hypothetical phenomenon in which a gravitational wave packet is confined to a compact region of spacetime by the gravitational attraction of its own field energy.

With Kip Thorne, Hartle derived from general relativity the laws of motion and precession of black holes and other relativistic bodies, including the influence of the coupling of their multipole moments to the spacetime curvature of nearby objects, as well as writing down the Hartle–Thorne metric, an approximate solution which describes the exterior of a slowly and rigidly rotating, stationary and axially symmetric body.

Working at the Enrico Fermi Institute at the University of Chicago in 1983, he developed the Hartle–Hawking wavefunction of the Universe in collaboration with Stephen Hawking. This specific solution to the Wheeler–deWitt equation is meant to explain the initial conditions of the Big Bang cosmology.

Hartle's textbook on general relativity, Gravity: An Introduction to Einstein's General Relativity, was published in 2003.

Hartle was a founder of the Kavli Institute for Theoretical Physics and served as its director from 1995 to 1997.

He was elected to the American Philosophical Society in 2016. He also was an American Physical Society Fellow, and a Guggenheim Fellow, was elected to the National Academy of Sciences, and received the 2009 APS Einstein Prize.

Personal life
Hartle married Mary Jo Wheeler in 1984, the niece of John Wheeler.

Hartle died in Zurich (Switzerland) on May 17, 2023, at the age of 83.