David Joseph Bohm (; 20 December 1917 – 27 October 1992) was an American-Brazilian physicist who has been described as one of the most significant theoretical physicists of the 20th centuryDavid Peat Who's Afraid of Schrödinger's Cat? The New Science Revealed: Quantum Theory, Relativity, Chaos and the New Cosmology 1997, pp. 316–317 and who contributed unorthodox ideas to quantum theory, neuropsychology, and the philosophy of mind. Among his many contributions to physics is his causal and deterministic interpretation of quantum theory, known as De Broglie–Bohm theory.
Bohm advanced the view that quantum physics meant that the old Cartesian model of reality—that there are two kinds of substance, the mental and the physical, that somehow interact—was too limited. To complement it, he developed a mathematical and physical theory of "implicate" and "explicate" order.David Bohm: Wholeness and the Implicate Order, Routledge, 1980 (). He also believed that the brain, at the cellular level, works according to the mathematics of some quantum effects, and postulated that thought is distributed and non-localised just as quantum entities are. . Bohm's main concern was with understanding the nature of reality in general and of consciousness in particular as a coherent whole, which according to Bohm is never static or complete.Wholeness and the Implicate Order, Bohm – 4 July 2002
Bohm warned of the dangers of rampant reason and technology, advocating instead the need for genuine supportive dialogue, which he claimed could bridge and unify conflicting and troublesome divisions in the social world.David Bohm: On Dialogue (2004) Routledge
Born in the United States, Bohm obtained his Ph.D. under J. Robert Oppenheimer at the University of California, Berkeley. His Communist affiliations made him the subject of a federal government investigation in 1949, leading to his suspension from Princeton University and prompting him to leave the U.S. He pursued his career in several countries, becoming first a Brazilian and then a British citizen. He abandoned Marxism in the wake of the Hungarian Uprising in 1956.
Youth and college Bohm was born in Wilkes-Barre, Pennsylvania, to an Austrian Jewish immigrant father, Samuel Bohm, – By the Numbers – David Bohm and a Lithuanian Jewish mother, Frieda Popky. He was raised mainly by his father, a furniture-store owner and assistant of the local rabbi. Despite being raised in a Jewish family, he became an agnostic in his teenage years.Peat 1997, p.21. "If he identified Jewish lore and customs with his father, then this was a way he would distance himself from Samuel. By the time he reached his late teens, he had become firmly agnostic." Bohm attended Pennsylvania State College (now Pennsylvania State University), graduating in 1939, and then the California Institute of Technology, for one year. He then transferred to the theoretical physics group directed by Robert Oppenheimer at the University of California, Berkeley Radiation Laboratory, where he obtained his doctorate.
Bohm lived in the same neighborhood as some of Oppenheimer's other graduate students (Giovanni Rossi Lomanitz, Joseph Weinberg, and Max Friedman) and with them became increasingly involved in radical politics. He was active in communist and communist-backed organizations, including the Young Communist League, the Campus Committee to Fight Conscription, and the Committee for Peace Mobilization. During his time at the Radiation Laboratory, Bohm was in a relationship with Betty Friedan and also helped to organize a local chapter of the Federation of Architects, Engineers, Chemists and Technicians, a small labor union affiliated to the Congress of Industrial Organizations (CIO).
Work and doctorate
Manhattan Project contributions During World War II, the Manhattan Project mobilized much of Berkeley's physics research in the effort to produce the first atomic bomb. Though Oppenheimer had asked Bohm to work with him at Los Alamos (the top-secret laboratory established in 1942 to design the atom bomb), the project's director, Brigadier General Leslie Groves, would not approve Bohm's security clearance after seeing evidence of his politics and his close friendship with Weinberg, who had been suspected of espionage.
During the war, Bohm remained at Berkeley, where he taught physics and conducted research in plasma, the synchrotron and the synchrocyclotron. He completed his PhD in 1943 by an unusual circumstance. According to biographer F. David Peat,Peat 1997, p. 64 "The scattering calculations (of collisions of protons and deuterons) that he had completed proved useful to the Manhattan Project and were immediately classified. Without security clearance, Bohm was denied access to his own work; not only would he be barred from defending his thesis, he was not even allowed to write his own thesis in the first place!" To satisfy the university, Oppenheimer certified that Bohm had successfully completed the research. Bohm later performed theoretical calculations for the Calutrons at the Y-12 facility in Oak Ridge, Tennessee. These calculations were used for the electromagnetic enrichment of uranium for the bomb dropped on Hiroshima in 1945.
McCarthyism and leaving the United States After the war, Bohm became an assistant professor at Princeton University. He also worked closely with Albert Einstein at the nearby Institute for Advanced Study. In May 1949, the House Un-American Activities Committee called upon Bohm to testify because of his previous ties to unionism and suspected communists. Bohm invoked his Fifth Amendment right to refuse to testify, and he refused to give evidence against his colleagues.
In 1950, Bohm was arrested for refusing to answer the committee's questions. He was acquitted in May 1951, but Princeton had already suspended him. After his acquittal, Bohm's colleagues sought to have him reinstated at Princeton, but Princeton President Harold W. DoddsRussell Olwell: Physics and Politics in Cold War America: The Two Exiles of David Bohm, Working Paper Number 20. Program in Science, Technology, and Society. Massachusetts Institute of Technology. decided not to renew Bohm's contract. Although Einstein considered appointing him as his research assistant at the institute, IAS President Oppenheimer "opposed the idea and [...] advised his former student to leave the country". His request to go to the University of Manchester received Einstein's support but was unsuccessful.Albert Einstein to Patrick Blackett, 17 April 1951 (Albert Einstein archives). Cited after Olival Freire, Jr.: Science and Exile: David Bohm, the cold war, and a new interpretation of quantum mechanics, HSPS, vol. 36, Part 1, pp. 1–34, ISSN 0890-9997, 2005, see footnote 8. . Bohm then left for Brazil to assume a professorship of physics at the University of São Paulo, at Jayme Tiomno's invitation and on the recommendation of both Einstein and Oppenheimer.
Quantum theory and Bohm diffusion
During his early period, Bohm made a number of significant contributions to physics, particularly quantum mechanics and relativity theory. As a postgraduate at Berkeley, he developed a theory of plasmas, discovering the electron phenomenon known as Bohm diffusion.D. Bohm: The characteristics of electrical discharges in magnetic fields, in: A. Guthrie, R. K. Wakerling (eds.), McGraw–Hill, 1949. His first book, Quantum Theory, published in 1951, was well received by Einstein, among others. But Bohm became dissatisfied with the orthodox interpretation of quantum theory he wrote about in that book. Starting from the realization that the WKB approximation of quantum mechanics leads to deterministic equations and convinced that a mere approximation could not turn a probabilistic theory into a deterministic theory, he doubted the inevitability of the conventional approach to quantum mechanics.Maurice A. de Gosson, Basil J. Hiley: Zeno paradox for Bohmian trajectories: the unfolding of the metatron, 3 January 2011 (PDF – retrieved 16 February 2012).
Bohm's aim was not to set out a deterministic, mechanical viewpoint but to show that it was possible to attribute properties to an underlying reality, in contrast to the conventional approach.B. J. Hiley: Some remarks on the evolution of Bohm's proposals for an alternative to quantum mechanics, 30 January 2010. He began to develop his own interpretation (the De Broglie–Bohm theory, also called the pilot wave theory), the predictions of which agreed perfectly with the non-deterministic quantum theory. He initially called his approach a hidden variable theory, but he later called it ontological theory, reflecting his view that a stochastic process underlying the phenomena described by his theory might one day be found. Bohm and his colleague Basil Hiley later stated that they had found their own choice of terms of an "interpretation in terms of hidden variables" to be too restrictive, especially since their variables, position and momentum, "are not actually hidden".David Bohm, Basil Hiley: The Undivided Universe: An Ontological Interpretation of Quantum Theory, edition published in the Taylor & Francis e-library 2009 (first edition Routledge, 1993), , p. 2.
Bohm's work and the EPR argument became the major factor motivating John Stewart Bell's inequality, which rules out local hidden variable theories; the full consequences of Bell's work are still being investigated.
Brazil When Bohm arrived in Brazil on 10 October 1951, the US Consul in São Paulo confiscated his passport, informing him he could retrieve it only to return to his country, which reportedly frightened BohmRussell Olwell: Physics and politics in cold war America: the two exiles of David Bohm, Working Paper Number 2, Working Program in Science, Technology, and Society; Massachusetts Institute of Technology and significantly lowered his spirits, as he had hoped to travel to Europe. He applied for and received Brazilian citizenship, but by law, had to give up his US citizenship; he was able to reclaim it only decades later, in 1986, after pursuing a lawsuit.Olival Freire, Jr.: Science and Exile: David Bohm, the cold war, and a new interpretation of quantum mechanics , HSPS, vol. 36, part 1, pp. 1–34, ISSN 0890-9997, 2005
At the University of São Paulo, Bohm worked on the causal theory that became the subject of his publications in 1952. Jean-Pierre Vigier traveled to São Paulo, where he worked with Bohm for three months; Ralph Schiller, student of cosmologist Peter Bergmann, was his assistant for two years; he worked with Tiomno and Walther Schützer; and Mario Bunge stayed to work with him for one year. He was in contact with Brazilian physicists Mário Schenberg, Jean Meyer, Leite Lopes, and had discussions on occasion with visitors to Brazil, including Richard Feynman, Isidor Rabi, Léon Rosenfeld, Carl Friedrich von Weizsäcker, Herbert L. Anderson, Donald Kerst, Marcos Moshinsky, Alejandro Medina, and the former assistant to Heisenberg, Guido Beck, who encouraged him in his work and helped him obtain funding. The Brazilian CNPq explicitly supported his work on the causal theory and funded several researchers around Bohm. His work with Vigier was the beginning of a long-standing cooperation between the two and Louis De Broglie, in particular, on connections to the hydrodynamics model proposed by Madelung.
Yet the causal theory met much resistance and skepticism, with many physicists holding the Copenhagen interpretation to be the only viable approach to quantum mechanics. Bohm and Vigier both emphasized causality, not determinism. In this context, Bohm proposed a causal approach in which the material world could be represented at an infinite number of levels, with stochastic dynamics at every level.
From 1951 to 1953, Bohm and David Pines published the articles in which they introduced the random phase approximation and proposed the plasmon.
Bohm and Aharonov form of the EPR paradox