James Burkett Hartle is an American physicist

Physicist

A physicist is a scientist who studies or practices physics. Physicists study a wide range of physical phenomena in many branches of physics spanning all length scales: from sub-atomic particles of which all ordinary matter is made to the behavior of the material Universe as a whole...

. He has been a professor of physics at the University of California, Santa Barbara

University of California, Santa Barbara

The University of California, Santa Barbara, commonly known as UCSB or UC Santa Barbara, is a public research university and one of the 10 general campuses of the University of California system. The main campus is located on a site in Goleta, California, from Santa Barbara and northwest of Los...

 since 1966, and he is currently a member of the external faculty of the Santa Fe Institute

Santa Fe Institute

The Santa Fe Institute is an independent, nonprofit theoretical research institute located in Santa Fe and dedicated to the multidisciplinary study of the fundamental principles of complex adaptive systems, including physical, computational, biological, and social systems.The Institute houses a...

. Hartle is known for his work in general relativity

General relativity

General relativity or the general theory of relativity is the geometric theory of gravitation published by Albert Einstein in 1916. It is the current description of gravitation in modern physics...

, astrophysics

Astrophysics

Astrophysics is the branch of astronomy that deals with the physics of the universe, including the physical properties of celestial objects, as well as their interactions and behavior...

, and interpretation of quantum mechanics

Interpretation of quantum mechanics

An interpretation of quantum mechanics is a set of statements which attempt to explain how quantum mechanics informs our understanding of nature. Although quantum mechanics has held up to rigorous and thorough experimental testing, many of these experiments are open to different interpretations...

.

In collaboration with Murray Gell-Mann

Murray Gell-Mann

Murray Gell-Mann is an American physicist and linguist who received the 1969 Nobel Prize in physics for his work on the theory of elementary particles...

 and others, Hartle developed an alternative to the standard Copenhagen interpretation

Copenhagen interpretation

The Copenhagen interpretation is one of the earliest and most commonly taught interpretations of quantum mechanics. It holds that quantum mechanics does not yield a description of an objective reality but deals only with probabilities of observing, or measuring, various aspects of energy quanta,...

, more general and appropriate to quantum cosmology

Quantum cosmology

In theoretical physics, quantum cosmology is a field attempting to study the effect of quantum mechanics on the formation of the universe, or its early evolution, especially just after the Big Bang...

, based on consistent histories

Consistent histories

In quantum mechanics, the consistent histories approach is intended to give a modern interpretation of quantum mechanics, generalising the conventional Copenhagen interpretation and providing a natural interpretation of quantum cosmology...

.

With Dieter Brill in 1964, he discovered the Brill-Hartle geon, an approximate solution realizing Wheeler

John Archibald Wheeler

John Archibald Wheeler was an American theoretical physicist who was largely responsible for reviving interest in general relativity in the United States after World War II. Wheeler also worked with Niels Bohr in explaining the basic principles behind nuclear fission...

'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.

Working at the Enrico Fermi Institute

Enrico Fermi Institute

The Institute for Nuclear Studies was founded September, 1945 as part of the University of Chicago with Samuel King Allison as director. On November 20, 1955 it was renamed The Enrico Fermi Institute for Nuclear Studies...

 at the University of Chicago

University of Chicago

The University of Chicago is a private research university in Chicago, Illinois, USA. It was founded by the American Baptist Education Society with a donation from oil magnate and philanthropist John D. Rockefeller and incorporated in 1890...

 in 1983, he developed the Hartle-Hawking wavefunction

Hartle-Hawking state

The Hartle-Hawking state is a proposal concerning the state of the universe prior to the Planck epoch. Hartle-Hawking is essentially a no-boundary proposal that the universe is infinitely finite: that there was no time before the Big Bang because time did not exist before the formation of spacetime...

 of the Universe in collaboration with Stephen Hawking

Stephen Hawking

Stephen William Hawking, CH, CBE, FRS, FRSA is an English theoretical physicist and cosmologist, whose scientific books and public appearances have made him an academic celebrity...

. This specific solution to the Wheeler-deWitt equation

Wheeler-deWitt equation

In theoretical physics, the Wheeler–DeWitt equation is a functional differential equation. It is ill defined in the general case, but very important in theoretical physics, especially in quantum gravity. It is a functional differential equation on the space of three dimensional spatial metrics...

 is meant to explain the initial conditions of the Big Bang

Big Bang

The Big Bang theory is the prevailing cosmological model that explains the early development of the Universe. According to the Big Bang theory, the Universe was once in an extremely hot and dense state which expanded rapidly. This rapid expansion caused the young Universe to cool and resulted in...

 cosmology.

Hartle is the author of the textbook on general relativity entitled Gravity: an Introduction to Einstein's General Relativity.

External links

• James Hartle homepage
• Hartle faculty profile
• "The Future of Gravity" – April, 2000 online lecture (Realaudio
  RealAudio
  RealAudio is a proprietary audio format developed by RealNetworks and first released in April 1995. It uses a variety of audio codecs, ranging from low-bitrate formats that can be used over dialup modems, to high-fidelity formats for music. It can also be used as a streaming audio format, that is...
  
  plus slides)
• "Spacetime Quantum Mechanics" online Realaudio lecture
• "The Classical Behavior of Quantum Universes" online Realaudio lecture
• Index to more Hartle lectures online