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| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| David Bohm | 2/5 | https://en.wikipedia.org/wiki/David_Bohm | reference | science, encyclopedia | 2026-05-05T09:27:05.696760+00:00 | kb-cron |
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. 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. 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. 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". 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 Bohm 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. 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 === In 1955, Bohm relocated to Israel, where he spent two years working at the Technion, in Haifa. There, he met Sarah Woolfson, whom he married in 1956. In 1957, Bohm and his student Yakir Aharonov published a new version of the Einstein–Podolsky–Rosen (EPR) paradox, reformulating the original argument in terms of spin. It was that form of the EPR paradox that was discussed by John Stewart Bell in his famous paper of 1964.
=== Aharonov–Bohm effect ===
In 1957, Bohm relocated to the United Kingdom as a research fellow at the University of Bristol. In 1959, Bohm and Aharonov discovered the Aharonov–Bohm effect, showing how a magnetic field could affect a region of space in which the field had been shielded, but its vector potential did not vanish there. That showed for the first time that the magnetic vector potential, hitherto a mathematical convenience, could have real physical (quantum) effects. In 1961, Bohm was made professor of theoretical physics at the University of London's Birkbeck College, becoming emeritus in 1987. His collected papers are stored there.
=== Implicate and explicate order ===
At Birkbeck College, much of the work of Bohm and Basil Hiley expanded on the notion of implicate, explicate, and generative orders proposed by Bohm. In the view of Bohm and Hiley, "things, such as particles, objects, and indeed subjects" exist as "semi-autonomous quasi-local features" of an underlying activity. Such features can be considered to be independent only up to a certain level of approximation in which certain criteria are fulfilled. In that picture, the classical limit for quantum phenomena, in terms of a condition that the action function is not much greater than the Planck constant, indicates one such criterion. They used the word "holomovement" for the activity in such orders.
=== Holonomic model of the brain ===
In collaboration with Stanford University neuroscientist Karl H. Pribram, Bohm was involved in the early development of the holonomic model of the functioning of the brain, a model for human cognition that is drastically different from conventionally-accepted ideas. Bohm worked with Pribram on the theory that the brain operates in a manner that is similar to a hologram, in accordance with quantum mathematical principles and the characteristics of wave patterns.