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Thursday, September 4, 2014

Paul Dirac

Paul Dirac

From Wikipedia, the free encyclopedia

Paul Dirac
Dirac 4.jpg
Born Paul Adrien Maurice Dirac
8 August 1902
Bristol, England
Died 20 October 1984 (aged 82)
Tallahassee, Florida, USA
Residence United Kingdom
Nationality Switzerland (1902–19)
United Kingdom (1919–84)
Fields Physics (theoretical)
Institutions University of Cambridge
University of Miami
Florida State University
Alma mater University of Bristol
University of Cambridge
Doctoral advisor Ralph Fowler
Doctoral students Homi Bhabha
Harish Chandra Mehta
Dennis Sciama
Fred Hoyle
Behram Kurşunoğlu
John Polkinghorne
Known for
Notable awards Nobel Prize in Physics (1933)
Royal Medal (1939)
Copley Medal (1952)
Max Planck Medal (1952)
Fellow of the Royal Society (1930)[1]

Paul Adrien Maurice Dirac OM FRS[2] (/dɪˈræk/ di-RAK; 8 August 1902 – 20 October 1984) was an English theoretical physicist who made fundamental contributions to the early development of both quantum mechanics and quantum electrodynamics. He was the Lucasian Professor of Mathematics at the University of Cambridge, a member of the Center for Theoretical Studies, University of Miami, and spent the last decade of his life at Florida State University.

Among other discoveries, he formulated the Dirac equation, which describes the behaviour of fermions and predicted the existence of antimatter. Dirac shared the Nobel Prize in Physics for 1933 with Erwin Schrödinger, "for the discovery of new productive forms of atomic theory".[3] He also did work that forms the basis of modern attempts to reconcile general relativity with quantum mechanics.

He was regarded by his friends and colleagues as unusual in character. Albert Einstein said of him, "This balancing on the dizzying path between genius and madness is awful",.[4] His mathematical brilliance, however, means he is regarded as one of the most significant physicists of the 20th century.

Personal life

Early years

Paul Adrien Maurice Dirac was born at his parents' home in Bristol, England, on 8 August 1902,[5] and grew up in the Bishopston area of the city.[6] His father, Charles Adrien Ladislas Dirac, was an immigrant from Saint-Maurice, Switzerland, who worked in Bristol as a French teacher. His mother, Florence Hannah Dirac, née Holten, the daughter of a ship's captain, was born in Cornwall, England, and worked as a librarian at the Bristol Central Library. Paul had a younger sister, Béatrice Isabelle Marguerite, known as Betty, and an older brother, Reginald Charles Félix, known as Felix,[7][8] who committed suicide in March 1925.[9] Dirac later recalled: "My parents were terribly distressed. I didn't know they cared so much [...] I never knew that parents were supposed to care for their children, but from then on I knew."[10]

Charles and the children were officially Swiss nationals until they became naturalised on 22 October 1919.[11] Dirac's father was strict and authoritarian, although he disapproved of corporal punishment.[12] Dirac had a strained relationship with his father, so much so that after his father's death, Dirac wrote, "I feel much freer now, and I am my own man." Charles forced his children to speak to him only in French, in order that they learn the language. When Dirac found that he could not express what he wanted to say in French, he chose to remain silent.[13][14]

Education

Dirac was educated first at Bishop Road Primary School[15] and then at the all-boys Merchant Venturers' Technical College (later Cotham School), where his father was a French teacher.[16] The school was an institution attached to the University of Bristol, which shared grounds and staff.[17] It emphasised technical subjects like bricklaying, shoemaking and metal work, and modern languages.[18] This was unusual at a time when secondary education in Britain was still dedicated largely to the classics, and something for which Dirac would later express gratitude.[17]

Dirac studied electrical engineering on a City of Bristol University Scholarship at the University of Bristol's engineering faculty, which was co-located with the Merchant Venturers' Technical College.[19] Shortly before he completed his degree in 1921, he sat the entrance examination for St John's College, Cambridge. He passed, and was awarded a £70 scholarship, but this fell short of the amount of money required to live and study at Cambridge. Despite his having graduated with a first class honours Bachelor of Science degree in engineering, the economic climate of the post-war depression was such that he was unable to find work as an engineer. Instead he took up an offer to study for a Bachelor of Arts degree in mathematics at the University of Bristol free of charge. He was permitted to skip the first year of the course owing to his engineering degree.[20]

In 1923, Dirac graduated, once again with first class honours, and received a £140 scholarship from the Department of Scientific and Industrial Research.[21] Along with his £70 scholarship from St John's College, this was enough to live at Cambridge. There, Dirac pursued his interests in the theory of general relativity, an interest he had gained earlier as a student in Bristol, and in the nascent field of quantum physics, under the supervision of Ralph Fowler.[22] From 1925 to 1928 he held an 1851 Research Fellowship from the Royal Commission for the Exhibition of 1851.[23] He completed his PhD in June 1926 with the first thesis on quantum mechanics to be submitted anywhere.[24] He then continued his research in Copenhagen and Göttingen.[23]

Family


Paul Dirac with his wife in Copenhagen, July 1963

Dirac married Margit Wigner (Eugene Wigner's sister), in 1937. He adopted Margit's two children, Judith and Gabriel. Paul and Margit Dirac had two children together, both daughters, Mary Elizabeth and Florence Monica.

Margit, known as Manci, visited her brother in 1934 in Princeton, New Jersey, from her native Hungary and, while at dinner at the Annex Restaurant met the "lonely-looking man at the next table." This account from a Korean physicist, Y. S. Kim, who met and was influenced by Dirac, also says: "It is quite fortunate for the physics community that Manci took good care of our respected Paul A. M. Dirac. Dirac published eleven papers during the period 1939–46.... Dirac was able to maintain his normal research productivity only because Manci was in charge of everything else."[25]

Personality

Dirac was known among his colleagues for his precise and taciturn nature. His colleagues in Cambridge jokingly defined a unit of a "dirac", which was one word per hour.[26] When Niels Bohr complained that he did not know how to finish a sentence in a scientific article he was writing, Dirac replied, "I was taught at school never to start a sentence without knowing the end of it."[27] He criticised the physicist J. Robert Oppenheimer's interest in poetry: "The aim of science is to make difficult things understandable in a simpler way; the aim of poetry is to state simple things in an incomprehensible way. The two are incompatible."[28]

Dirac himself wrote in his diary during his postgraduate years that he concentrated solely on his research, and stopped only on Sunday, when he took long strolls alone.[29]

An anecdote recounted in a review of the 2009 biography tells of Werner Heisenberg and Dirac sailing on an ocean liner to a conference in Japan in August 1929. "Both still in their twenties, and unmarried, they made an odd couple. Heisenberg was a ladies' man who constantly flirted and danced, while Dirac—'an Edwardian geek', as biographer Graham Farmelo puts it—suffered agonies if forced into any kind of socialising or small talk. 'Why do you dance?' Dirac asked his companion. 'When there are nice girls, it is a pleasure,' Heisenberg replied. Dirac pondered this notion, then blurted out: 'But, Heisenberg, how do you know beforehand that the girls are nice?'"[30]

According to a story told in different versions, a friend or student visited Dirac, not knowing of his marriage. Noticing the visitor's surprise at seeing an attractive woman in the house, Dirac said, "This is... this is Wigner's sister". Margit Dirac told both George Gamow and Anton Capri in the 1960s that her husband had actually said, "Allow me to present Wigner's sister, who is now my wife."[31][32]

Another story told of Dirac is that when he first met the young Richard Feynman at a conference, he said after a long silence "I have an equation. Do you have one too?".[33]

After he presented a lecture at a conference, one colleague raised his hand and said "I don't understand the equation on the top-right-hand corner of the blackboard". After a long silence, the moderator asked Dirac if he wanted to answer the question, to which Dirac replied "That was not a question, it was a comment."[34][35]

Dirac was also noted for his personal modesty. He called the equation for the time evolution of a quantum-mechanical operator, which he was the first to write down, the "Heisenberg equation of motion". Most physicists speak of Fermi–Dirac statistics for half-integer-spin particles and Bose–Einstein statistics for integer-spin particles. While lecturing later in life, Dirac always insisted on calling the former "Fermi statistics". He referred to the latter as "Einstein statistics" for reasons, he explained, of "symmetry".[citation needed]

Religious views

Heisenberg recollected a conversation among young participants at the 1927 Solvay Conference about Einstein and Planck's views on religion between Wolfgang Pauli, Heisenberg and Dirac. Dirac's contribution was a criticism of the political purpose of religion, which was much appreciated for its lucidity by Bohr when Heisenberg reported it to him later. Among other things, Dirac said:


Heisenberg's view was tolerant. Pauli, raised as a Catholic, had kept silent after some initial remarks, but when finally he was asked for his opinion, said: "Well, our friend Dirac has got a religion and its guiding principle is 'There is no God and Paul Dirac is His prophet.'" Everybody, including Dirac, burst into laughter.[37][38]

Later in life, Dirac's views towards the idea of God were less acerbic. As an author of an article appearing in the May 1963 edition of Scientific American, Dirac wrote:


In 1971, at a conference meeting, Dirac expressed his views on the existence of God.[40] Dirac explained that the existence of God could only be justified if an improbable event were to have taken place in the past:


Dirac did not commend himself to any definite view, but he described the possibilities for answering the question of God in a scientific manner.[40]

Honours

Dirac shared the 1933 Nobel Prize for physics with Erwin Schrödinger "for the discovery of new productive forms of atomic theory".[3] Dirac was also awarded the Royal Medal in 1939 and both the Copley Medal and the Max Planck Medal in 1952. He was elected a Fellow of the Royal Society in 1930,[2] an Honorary Fellow of the American Physical Society in 1948, and an Honorary Fellow of the Institute of Physics, London in 1971. Dirac became a member of the Order of Merit in 1973, having previously turned down a knighthood as he did not want to be addressed by his first name.[30][41]

Death


Dirac's grave in Roselawn cemetery, Tallahassee, Florida. Also buried is his wife Manci (Margit Wigner).

In 1984, Dirac died in Tallahassee, Florida, and was buried at Tallahassee's Roselawn Cemetery.[42][43] Dirac's childhood home in Bristol is commemorated with a blue plaque and the nearby Dirac Road is named in recognition of his links with the city. A commemorative stone was erected in a garden in Saint-Maurice, Switzerland, the town of origin of his father's family, on 1 August 1991. On 13 November 1995 a commemorative marker, made from Burlington green slate and inscribed with the Dirac equation, was unveiled in Westminster Abbey.[42][44] The Dean of Westminster, Edward Carpenter, had initially refused permission for the memorial, thinking Dirac to be anti-Christian, but was eventually (over a five-year period) persuaded to relent.[45]

Career

Dirac established the most general theory of quantum mechanics and discovered the relativistic equation for the electron, which now bears his name. The remarkable notion of an antiparticle to each fermion particle – e.g. the positron as antiparticle to the electron – stems from his equation. He was the first to develop quantum field theory, which underlies all theoretical work on sub-atomic or "elementary" particles today, work that is fundamental to our understanding of the forces of nature.
He proposed and investigated the concept of a magnetic monopole, an object not yet known empirically, as a means of bringing even greater symmetry to James Clerk Maxwell's equations of electromagnetism.

Gravity

He quantised the gravitational field, and developed a general theory of quantum field theories with dynamical constraints, which forms the basis of the gauge theories and superstring theories of today. The influence and importance of his work has increased with the decades, and physicists daily use the concepts and equations that he developed.

Quantum theory

Dirac's first step into a new quantum theory was taken late in September 1925. Ralph Fowler, his research supervisor, had received a proof copy of an exploratory paper by Werner Heisenberg in the framework of the old quantum theory of Bohr and Sommerfeld, which leaned heavily on Bohr's correspondence principle but changed the equations so that they involved directly observable quantities. Fowler sent Heisenberg's paper on to Dirac, who was on vacation in Bristol, asking him to look into this paper carefully.

Dirac's attention was drawn to a mysterious mathematical relationship, at first sight unintelligible, that Heisenberg had reached. Several weeks later, back in Cambridge, Dirac suddenly recognised that this mathematical form had the same structure as the Poisson Brackets that occur in the classical dynamics of particle motion. From this thought he quickly developed a quantum theory that was based on non-commuting dynamical variables. This led him to a more profound and significant general formulation of quantum mechanics than was achieved by any other worker in this field.[46]

Dirac noticed an analogy between the Poisson brackets of classical mechanics and the recently proposed quantisation rules in Werner Heisenberg's matrix formulation of quantum mechanics. This observation allowed Dirac to obtain the quantisation rules in a novel and more illuminating manner. For this work, published in 1926, he received a PhD from Cambridge.

The Dirac equation

In 1928, building on 2×2 spin matrices which he discovered independently of Wolfgang Pauli's work on non-relativistic spin systems, (Abraham Pais quoted Dirac as saying "I believe I got these (matrices) independently of Pauli and possibly Pauli got these independently of me")[47] he proposed the Dirac equation as a relativistic equation of motion for the wave function of the electron.[48] This work led Dirac to predict the existence of the positron, the electron's antiparticle, which he interpreted in terms of what came to be called the Dirac sea.[49] The positron was observed by Carl Anderson in 1932. Dirac's equation also contributed to explaining the origin of quantum spin as a relativistic phenomenon.

The necessity of fermions (matter being created and destroyed in Enrico Fermi's 1934 theory of beta decay), however, led to a reinterpretation of Dirac's equation as a "classical" field equation for any point particle of spin ħ/2, itself subject to quantisation conditions involving anti-commutators. Thus reinterpreted, in 1934 by Werner Heisenberg, as a (quantum) field equation accurately describing all elementary matter particles – today quarks and leptons – this Dirac field equation is as central to theoretical physics as the Maxwell, Yang–Mills and Einstein field equations. Dirac is regarded as the founder of quantum electrodynamics, being the first to use that term. He also introduced the idea of vacuum polarisation in the early 1930s. This work was key to the development of quantum mechanics by the next generation of theorists, and in particular Schwinger, Feynman, Sin-Itiro Tomonaga and Dyson in their formulation of quantum electrodynamics.

Dirac's Principles of Quantum Mechanics, published in 1930, is a landmark in the history of science. It quickly became one of the standard textbooks on the subject and is still used today. In that book, Dirac incorporated the previous work of Werner Heisenberg on matrix mechanics and of Erwin Schrödinger on wave mechanics into a single mathematical formalism that associates measurable quantities to operators acting on the Hilbert space of vectors that describe the state of a physical system. The book also introduced the delta function. Following his 1939 article,[50] he also included the bra–ket notation in the third edition of his book,[51] thereby contributing to its universal use nowadays.

Magnetic monopoles

In 1933, following his 1931 paper on magnetic monopoles, Dirac showed that the existence of a single magnetic monopole in the universe would suffice to explain the observed quantisation of electrical charge. In 1975,[52] 1982,[53] and 2009[54][55][56] intriguing results suggested the possible detection of magnetic monopoles, but there is, to date, no direct evidence for their existence.

Lucasian Chair

Dirac was the Lucasian Professor of Mathematics at Cambridge from 1932 to 1969. In 1937, he proposed a speculative cosmological model based on the so-called large numbers hypothesis. During World War II, he conducted important theoretical and experimental research on uranium enrichment by gas centrifuge.

Dirac's quantum electrodynamics (QED) made predictions that were – more often than not – infinite and therefore unacceptable. A workaround known as renormalisation was developed, but Dirac never accepted this. "I must say that I am very dissatisfied with the situation", he said in 1975, "because this so-called 'good theory' does involve neglecting infinities which appear in its equations, neglecting them in an arbitrary way. This is just not sensible mathematics. Sensible mathematics involves neglecting a quantity when it is small – not neglecting it just because it is infinitely great and you do not want it!"[57] His refusal to accept renormalisation resulted in his work on the subject moving increasingly out of the mainstream.

However, from his once rejected notes he managed to work on putting quantum electrodynamics on "logical foundations" based on Hamiltonian formalism that he formulated. He found a rather novel way of deriving the anomalous magnetic moment "Schwinger term" and also the Lamb shift, afresh in 1963, using the Heisenberg picture and without using the joining method used by Weisskopf and French, and by the two pioneers of modern QED, Schwinger and Feynman. That was two years before the Tomonaga–Schwinger–Feynman QED was given formal recognition by an award of the Nobel Prize for physics.

Weisskopf and French (FW) were the first to obtain the correct result for the Lamb shift and the anomalous magnetic moment of the electron. At first FW results did not agree with the incorrect but independent results of Feynman and Schwinger.[58] The 1963–1964 lectures Dirac gave on quantum field theory at Yeshiva University were published in 1966 as the Belfer Graduate School of Science, Monograph Series Number, 3. After having relocated to Florida to be near his elder daughter, Mary, Dirac spent his last fourteen years (of both life and physics research) at the University of Miami in Coral Gables, Florida, and Florida State University in Tallahassee, Florida.

In the 1950s in his search for a better QED, Paul Dirac developed the Hamiltonian theory of constraints[59] based on lectures that he delivered at the 1949 International Mathematical Congress in Canada. Dirac[60] had also solved the problem of putting the Tomonaga–Schwinger equation into the Schrödinger representation[61] and given explicit expressions for the scalar meson field (spin zero pion or pseudoscalar meson), the vector meson field (spin one rho meson), and the electromagnetic field (spin one massless boson, photon).

The Hamiltonian of constrained systems is one of Dirac's many masterpieces. It is a powerful generalisation of Hamiltonian theory that remains valid for curved spacetime. The equations for the Hamiltonian involve only six degrees of freedom described by g_{rs},p^{rs} for each point of the surface on which the state is considered. The g_{m0} (m = 0, 1, 2, 3) appear in the theory only through the variables g^{r0}, ( -{g^{00}} ) ^{-1/2} which occur as arbitrary coefficients in the equations of motion. There are four constraints or weak equations for each point of the surface x^0 = constant. Three of them H_r form the four vector density in the surface. The fourth H_L is a 3-dimensional scalar density in the surface HL ≈ 0; Hr ≈ 0 (r = 1, 2, 3)

In the late 1950s, he applied the Hamiltonian methods he had developed to cast Einstein's general relativity in Hamiltonian form[62] and to bring to a technical completion the quantisation problem of gravitation and bring it also closer to the rest of physics according to Salam and DeWitt. In 1959 he also gave an invited talk on "Energy of the Gravitational Field" at the New York Meeting of the American Physical Society later published in 1959 Phys Rev Lett 2, 368. In 1964 he published his Lectures on Quantum Mechanics (London:Academic) which deals with constrained dynamics of nonlinear dynamical systems including quantisation of curved spacetime. He also published a paper entitled "Quantization of the Gravitational Field" in the 1967 ICTP/IAEA Trieste Symposium on Contemporary Physics.

Students

Amongst his many students was John Polkinghorne, who recalls that Dirac "was once asked what was his fundamental belief. He strode to a blackboard and wrote that the laws of nature should be expressed in beautiful equations."[63]

Legacy

In 1975, Dirac gave a series of five lectures at the University of New South Wales which were subsequently published as a book, Directions in Physics (1978). He donated the royalties from this book to the university for the establishment of the Dirac Lecture Series. The Silver Dirac Medal for the Advancement of Theoretical Physics is awarded by the University of New South Wales to commemorate the lecture.[64]

Immediately after his death, two organisations of professional physicists established annual awards in Dirac's memory. The Institute of Physics, the United Kingdom's professional body for physicists, awards the Paul Dirac Medal for "outstanding contributions to theoretical (including mathematical and computational) physics".[65] The first three recipients were Stephen Hawking (1987), John Stewart Bell (1988), and Roger Penrose (1989). The International Centre for Theoretical Physics awards the Dirac Medal of the ICTP each year on Dirac's birthday (8 August).[66]

The Dirac-Hellman Award at Florida State University was endowed by Dr Bruce P. Hellman in 1997 to reward outstanding work in theoretical physics by FSU researchers.[67] The Paul A.M. Dirac Science Library at Florida State University, which Manci opened in December 1989,[citation needed] is named in his honour, and his papers are held there.[68] Outside is a statue of him by Gabriella Bollobás.[69] The street on which the National High Magnetic Field Laboratory in Tallahassee, Florida, is located was named Paul Dirac Drive. As well as in his home town of Bristol, there is also a road named after him in Didcot Oxfordshire, Dirac Way. The BBC named a video codec, Dirac, in his honour.

Publications

  • The Principles of Quantum Mechanics (1930): This book summarises the ideas of quantum mechanics using the modern formalism that was largely developed by Dirac himself. Towards the end of the book, he also discusses the relativistic theory of the electron (the Dirac equation), which was also pioneered by him. This work does not refer to any other writings then available on quantum mechanics.
  • Lectures on Quantum Mechanics (1966): Much of this book deals with quantum mechanics in curved space-time.
  • Lectures on Quantum Field Theory (1966): This book lays down the foundations of quantum field theory using the Hamiltonian formalism.
  • Spinors in Hilbert Space (1974): This book based on lectures given in 1969 at the University of Miami, Coral Gables, Florida, USA, deals with the basic aspects of spinors starting with a real Hilbert space formalism. Dirac concludes with the prophetic words "We have boson variables appearing automatically in a theory that starts with only fermion variables, provided the number of fermion variables is infinite. There must be such boson variables connected with electrons..."
  • General Theory of Relativity (1975): This 69-page work summarises Einstein's general theory of relativity.
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Wolfgang Pauli

Wolfgang Pauli

From Wikipedia, the free encyclopedia

Wolfgang Pauli
Wolfgang Pauli ETH-Bib Portr 01042.jpg
Born Wolfgang Ernst Pauli
25 April 1900
Vienna, Austria-Hungary
Died 15 December 1958 (aged 58)
Zurich, Switzerland
Citizenship Switzerland
Nationality Austria
Fields Physics
Institutions University of Göttingen
University of Copenhagen
University of Hamburg
ETH Zurich
Institute for Advanced Study
Alma mater Ludwig-Maximilians University
Doctoral advisor Arnold Sommerfeld
Other academic advisors Max Born
Doctoral students Nicholas Kemmer
Felix Villars
Other notable students Markus Fierz
Sigurd Zienau
Hans Frauenfelder
Known for Pauli exclusion principle
Pauli–Villars regularization
Pauli matrices
Pauli effect
Pauli equation
Pauli group
Pauli repulsion
Pauli–Lubanski pseudovector
Coining 'not even wrong'
Influences Ernst Mach
Carl Jung
Influenced Ralph Kronig
Notable awards Lorentz Medal (1931)
Nobel Prize in Physics (1945)
Matteucci Medal (1956)
Max Planck Medal (1958)
Notes
His godfather was Ernst Mach. He is not to be confused with Wolfgang Paul, whom Pauli called his "imaginary part",[1] a pun with the imaginary unit i.

Wolfgang Ernst Pauli (25 April 1900 – 15 December 1958) was an Austrian-born Swiss theoretical physicist and one of the pioneers of quantum physics.

In 1945, after having been nominated by Albert Einstein, Pauli received the Nobel Prize in Physics for his "decisive contribution through his discovery of a new law of Nature, the exclusion principle or Pauli principle." The discovery involved spin theory, which is the basis of a theory of the structure of matter.

Biography

Early years

Pauli was born in Vienna to a chemist Wolfgang Joseph Pauli (né Wolf Pascheles, 1869–1955) and his wife Bertha Camilla Schütz. His middle name was given in honor of his godfather, physicist Ernst Mach. Pauli's paternal grandparents were from prominent Jewish families of Prague; his great-grandfather was the Jewish publisher Wolf Pascheles.[2] Pauli's father converted from Judaism to Roman Catholicism shortly before his marriage in 1899. Pauli's mother, Bertha Schütz, was raised in her own mother's Roman Catholic religion; her father was Jewish writer Friedrich Schütz. Pauli was raised as a Roman Catholic, although eventually he and his parents left the Church.[3] He is considered to have been a deist and a mystic.[4][5]

Pauli attended the Döblinger-Gymnasium in Vienna, graduating with distinction in 1918. Only two months after graduation, the young prodigy published his first paper, on Albert Einstein's theory of general relativity. He attended the Ludwig-Maximilians University in Munich, working under Arnold Sommerfeld, where he received his PhD in July 1921 for his thesis on the quantum theory of ionized molecular hydrogen.

Sommerfeld asked Pauli to review the theory of relativity for the Encyklopädie der mathematischen Wissenschaften (Encyclopedia of Mathematical Sciences). Two months after receiving his doctorate, Pauli completed the article, which came to 237 pages. It was praised by Einstein; published as a monograph, it remains a standard reference on the subject to this day.
Wolfgang Pauli young.jpg

Pauli spent a year at the University of Göttingen as the assistant to Max Born, and the following year at the Institute for Theoretical Physics in Copenhagen, which later became the Niels Bohr Institute in 1965. From 1923 to 1928, he was a lecturer at the University of Hamburg. During this period, Pauli was instrumental in the development of the modern theory of quantum mechanics. In particular, he formulated the exclusion principle and the theory of nonrelativistic spin.

In 1928, he was appointed Professor of Theoretical Physics at ETH Zurich in Switzerland where he made significant scientific progress. He held visiting professorships at the University of Michigan in 1931, and the Institute for Advanced Study in Princeton in 1935. He was awarded the Lorentz Medal in 1931.

At the end of 1930, shortly after his postulation of the neutrino and immediately following his divorce in November, Pauli had a severe breakdown. He consulted psychiatrist and psychotherapist Carl Jung who, like Pauli, lived near Zurich. Jung immediately began interpreting Pauli's deeply archetypal dreams,[6] and Pauli became one of the depth psychologist’s best students. He soon began to criticize the epistemology of Jung’s theory scientifically, and this contributed to a certain clarification of the latter’s thoughts, especially about the concept of synchronicity. A great many of these discussions are documented in the Pauli/Jung letters, today published as Atom and Archetype. Jung's elaborate analysis of more than 400 of Pauli's dreams is documented in Psychology and Alchemy.

The German annexation of Austria in 1938 made him a German citizen, which became a problem for him in 1939 after the outbreak of World War II. In 1940, he tried in vain to obtain Swiss citizenship, which would have allowed him to remain at the ETH.[7]

Pauli moved to the United States in 1940, where he was employed as a professor of theoretical physics at the Institute for Advanced Study. In 1946, after the war, he became a naturalized citizen of the United States and subsequently returned to Zurich, where he mostly remained for the rest of his life. In 1949, he was granted Swiss citizenship.

In 1958, Pauli was awarded the Max Planck medal. In that same year, he fell ill with pancreatic cancer. When his last assistant, Charles Enz, visited him at the Rotkreuz hospital in Zurich, Pauli asked him: “Did you see the room number?” It was number 137. Throughout his life, Pauli had been preoccupied with the question of why the fine structure constant, a dimensionless fundamental constant, has a value nearly equal to 1/137. Pauli died in that room on 15 December 1958.

Scientific research

Niels Bohr, Werner Heisenberg, and Wolfgang Pauli, ca. 1935

Pauli made many important contributions in his career as a physicist, primarily in the field of quantum mechanics. He seldom published papers, preferring lengthy correspondences with colleagues such as Niels Bohr and Werner Heisenberg, with whom he had close friendships. Many of his ideas and results were never published and appeared only in his letters, which were often copied and circulated by their recipients.

Pauli proposed in 1924 a new quantum degree of freedom (or quantum number) with two possible values, in order to resolve inconsistencies between observed molecular spectra and the developing theory of quantum mechanics. He formulated the Pauli exclusion principle, perhaps his most important work, which stated that no two electrons could exist in the same quantum state, identified by four quantum numbers including his new two-valued degree of freedom. The idea of spin originated with Ralph Kronig. George Uhlenbeck and Samuel Goudsmit one year later identified Pauli's new degree of freedom as electron spin.

In 1926, shortly after Heisenberg published the matrix theory of modern quantum mechanics, Pauli used it to derive the observed spectrum of the hydrogen atom. This result was important in securing credibility for Heisenberg's theory.

Pauli introduced the 2 × 2 Pauli matrices as a basis of spin operators, thus solving the nonrelativistic theory of spin. This work is sometimes said to have influenced Paul Dirac in his creation of the Dirac equation for the relativistic electron, though Dirac stated that he invented these same matrices himself independently at the time, without Pauli's influence. Dirac invented similar but larger (4x4) spin matrices for use in his relativistic treatment of fermionic spin.

In 1930, Pauli considered the problem of beta decay. In a letter of 4 December to Lise Meitner et al., beginning, "Dear radioactive ladies and gentlemen", he proposed the existence of a hitherto unobserved neutral particle with a small mass, no greater than 1% the mass of a proton, in order to explain the continuous spectrum of beta decay. In 1934, Enrico Fermi incorporated the particle, which he called a neutrino, into his theory of beta decay. The neutrino was first confirmed experimentally in 1956 by Frederick Reines and Clyde Cowan, two and a half years before Pauli's death. On receiving the news, he replied by telegram: "Thanks for message. Everything comes to him who knows how to wait. Pauli."[8]

In 1940, he proved the spin-statistics theorem, a critical result of quantum field theory which states that particles with half-integer spin are fermions, while particles with integer spin are bosons.

In 1949, he published a paper on Pauli–Villars regularization: regularization is the term for techniques which modify infinite mathematical integrals to make them finite during calculations, so that one can identify whether the intrinsically infinite quantities in the theory (mass, charge, wavefunction) form a finite and hence calculable set which can be redefined in terms of their experimental values, which criterion is termed renormalization, and which removes infinities from quantum field theories, but also importantly allows the calculation of higher order corrections in perturbation theory.

Pauli made repeated criticisms of the modern synthesis of evolutionary biology,[9][10] and his contemporary admirers point to modes of epigenetic inheritance as supportive of his arguments.[11]

Personality and reputation

Wolfgang Pauli

The Pauli effect was named after the anecdotal bizarre ability of his to break experimental equipment simply by being in the vicinity. Pauli was aware of his reputation and was delighted whenever the Pauli effect manifested. These strange occurrences were in line with his investigations into the legitimacy of parapsychology, particularly his collaboration with C. G. Jung on the concept of synchronicity.

Regarding physics, Pauli was famously a perfectionist. This extended not just to his own work, but also to the work of his colleagues. As a result, he became known in the physics community as the "conscience of physics," the critic to whom his colleagues were accountable. He could be scathing in his dismissal of any theory he found lacking, often labelling it ganz falsch, utterly wrong.

However, this was not his most severe criticism, which he reserved for theories or theses so unclearly presented as to be untestable or unevaluatable and, thus, not properly belonging within the realm of science, even though posing as such. They were worse than wrong because they could not be proven wrong. Famously, he once said of such an unclear paper: It is not even wrong!"[12]

His supposed remark when meeting another leading physicist, Paul Ehrenfest, illustrates this notion of an arrogant Pauli. The two met at a conference for the first time. Ehrenfest was familiar with Pauli's papers and was quite impressed with them. After a few minutes of conversation, Ehrenfest remarked, "I think I like your Encyclopedia article [on relativity theory] better than I like you," to which Pauli shot back, "That's strange. With me, regarding you, it is just the opposite."[13] The two became very good friends from then on.

A somewhat warmer picture emerges from this story which appears in the article on Dirac:
"Werner Heisenberg [in Physics and Beyond, 1971] recollects a friendly conversation among young participants at the 1927 Solvay Conference, about Einstein and Planck's views on religion. Wolfgang Pauli, Heisenberg, and Dirac took part in it. Dirac's contribution was a poignant and clear criticism of the political manipulation of religion, that was much appreciated for its lucidity by Bohr, when Heisenberg reported it to him later. Among other things, Dirac said: "I cannot understand why we idle discussing religion. If we are honest – and as scientists honesty is our precise duty – we cannot help but admit that any religion is a pack of false statements, deprived of any real foundation. The very idea of God is a product of human imagination. [...] I do not recognize any religious myth, at least because they contradict one another. [...]" Heisenberg's view was tolerant. Pauli had kept silent, after some initial remarks. But when finally he was asked for his opinion, jokingly he said: "Well, I'd say that also our friend Dirac has got a religion and the first commandment of this religion is 'God does not exist and Paul Dirac is his prophet'". Everybody burst into laughter, including Dirac.
Many of Pauli's ideas and results were never published and appeared only in his letters, which were often copied and circulated by their recipients. Pauli may have been unconcerned that much of his work thus went uncredited, but when it came to Heisenberg's world-renowned, 1958, Lecture at Göttingen on their joint work on a unified field theory, and the press release calling Pauli a mere "assistant to Professor Heisenberg", Pauli became offended, shooting back several times at CERN and elsewhere by denouncing Heisenberg's physics prowess. The deterioration between them resulted in Heisenberg ignoring Pauli's funeral, and writing in his autobiography that Pauli's criticisms were overwrought.[14]

Personal life

In May 1929, Pauli left the Roman Catholic Church. In December of that year, he married Käthe Margarethe Deppner. The marriage was an unhappy one, ending in divorce in 1930 after less than a year. He married again in 1934 to Franziska Bertram. They had no children.

Bibliography

by Pauli
about Pauli
  • Enz, Charles P. (2002). No Time to be Brief, A scientific biography of Wolfgang Pauli. Oxford Univ. Press.
  • Enz, Charles P. (1995). "Rationales und Irrationales im Leben Wolfgang Paulis". In ed. H. Atmanspacher, et al. Der Pauli-Jung-Dialog. Berlin: Springer-Verlag.
  • Fischer, Ernst Peter (2004). Brücken zum Kosmos. Wolfgang Pauli – Denkstoffe und Nachtträume zwischen Kernphysik und Weltharmonie. Libelle. ISBN 978-3-909081-44-8.
  • Gieser, Suzanne (2005). The Innermost Kernel. Depth Psychology and Quantum Physics. Wolfgang Pauli's Dialogue with C.G. Jung. Springer Verlag.
  • Jung, C.G. (1980). Psychology and Alchemy. Princeton, New Jersey: Princeton Univ. Press.
  • Keve, Tom (2000). Triad: the physicists, the analysts, the kabbalists. London: Rosenberger & Krausz.
  • Lindorff, David (1994). Pauli and Jung: The Meeting of Two Great Minds. Quest Books.
  • Pais, Abraham (2000). The Genius of Science. Oxford: Oxford University Press.
  • Enz, P.; von Meyenn, Karl (editors); Schlapp, Robert (translator) (1994). Wolfgang Pauli – Writings on physics and philosophy. Berlin: Springer Verlag. ISBN 978-3-540-56859-9.
  • Laurikainen, K. V. (1988). Beyond the Atom – The Philosophical Thought of Wolfgang Pauli. Berlin: Springer Verlag. ISBN 0-387-19456-8.
  • Casimir, H. B. G. (1983). Haphazard Reality: Half a Century of Science. New York: Harper & Row. ISBN 0-06-015028-9.
  • Casimir, H. B. G. (1992). Het toeval van de werkelijkheid: Een halve eeuw natuurkunde. Amsterdam: Meulenhof. ISBN 90-290-9709-4.
  • Miller, Arthur I. (2009). Deciphering the Cosmic Number: The Strange Friendship of Wolfgang Pauli and Carl Jung. New York: W.W. Norton & Co. ISBN 978-0-393-06532-9.
  • Remo, F. Roth: Return of the World Soul, Wolfgang Pauli, C.G. Jung and the Challenge of Psychophysical Reality [unus mundus], Part 1: The Battle of the Giants. Pari Publishing, 2011, ISBN 978-88-95604-12-1.
  • Remo, F. Roth: Return of the World Soul, Wolfgang Pauli, C.G. Jung and the Challenge of Psychophysical Reality [unus mundus], Part 2: A Psychophysical Theory. Pari Publishing, 2012, ISBN 978-88-95604-16-9.
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