Paul Dirac

Paul Adrien Maurice Dirac (Bristol, August 8, 1902 - Tallahassee, October 20, 1984) was a British electrical engineer, mathematician, and theoretical physicist who made a fundamental contribution to the development of quantum mechanics and quantum electrodynamics.

He held the Lucasian Chair in mathematics at the University of Cambridge, although he spent the last ten years of his life at Florida State University. Among other discoveries he formulated the Dirac equation that describes the behavior of fermions and with which he predicted the existence of antimatter. Dirac shared the 1933 Nobel Prize in physics with Erwin Schrödinger, "for the discovery of productive new forms of atomic theory."

Biography

Paul Dirac was born in Bristol, England. His father, Charles, was an immigrant from the Swiss canton of Valais who taught French. His mother, originally from Cornwall, was the daughter of sailors. Paul had a younger sister (Beatrice Isabelle Marguerite) and an older brother (Reginald Charles Felix), who committed suicide at the age of twenty-six, in 1924. Dirac described his childhood as unhappy, due to the severity and authoritarianism of his father.. A recent biography has qualified this character, making reference to Paul's own difficult and taciturn character.

He studied at Bishop Primary School and at the Merchant Venturers Technical College, an institution of the University of Bristol, which emphasized modern science (something unusual at the time, and to which Dirac would be forever grateful).

He graduated with a degree in electrical engineering from the University of Bristol in 1921. After working briefly as an engineer, Dirac decided that his true calling was mathematics. He completed another degree in mathematics at Bristol in 1923 and was then admitted to Cambridge University, where he would spend most of his career. He became interested in the theory of relativity although Cunningham, a Cambridge specialist in that field, did not accept him as a student and so he worked under the supervision of Ralph Fowler who was working in the nascent field of quantum physics.

Scientific career

In 1926 he developed a version of quantum mechanics in which he united the previous work of Werner Heisenberg and that of Erwin Schrödinger into a single mathematical model that associates measurable quantities with operators acting on the Hilbert vector space and describes the state system physical. For this work he received a doctorate in physics from Cambridge.

In 1928, working on nonrelativistic Pauli spins, he found the Dirac equation, a relativistic equation that describes the electron. This work allowed Dirac to predict the existence of the positron, the antiparticle of the electron, which he interpreted to formulate the Dirac sea. The positron was first observed by Carl Anderson in 1932. Dirac also helped explain spin as a relativistic phenomenon.

Dirac's book Principles of Quantum Mechanics, published in 1930, became one of the most common textbooks on the subject and is still used today. He introduced the bra-ket notation and the Dirac delta function.

In 1931 Dirac showed that the existence of a single magnetic monopole in the universe would be enough to explain the quantization of electric charge.

On January 29, 2014, Professor David S. Hall of Amherst College Physics and Academy Research Fellow Mikko Möttönen of Aalto University report that they have successfully created, identified, and photographed magnetic monopoles synthetics in the laboratory.

Paul Dirac shared the 1933 Nobel Prize in Physics with Erwin Schrödinger "for the discovery of new productive atomic theories." Dirac held the Lucasian Professorship of Mathematics at Cambridge University where he taught from 1932 to 1969.

Dirac spent the last years of his life at Florida State University in Tallahassee, Florida. There he died in 1984, and a plaque in his honor was placed in Westminster Abbey in London in 1995.

Character and ideology

Dirac was known among his colleagues for his precise, yet taciturn nature. When Niels Bohr complained that he did not know how to end a certain sentence in a scientific paper, Dirac replied: "I was taught at school that you should never start a sentence without knowing the end of it." Anecdotes about his tendency to silence him became famous, and a unit, the dirac , was coined for the smallest unit of words that could be said in conversation. A recent biography The strangest man , by Graham Farmelo, has suggested that he had Asperger's Syndrome, as his language was very literal and he didn't talk much to people.

His difficulties with social relationships, his lack of empathy and his lack of interest in women were also known. Notwithstanding the latter, in 1937 he married the sister of the physicist Eugene Paul Wigner, Margit Wigner (known familiarly as Manci), with whom he had two daughters, in addition to two other sons that Manci contributed from a previous marriage, who adopted the surname Dirac, and whom he always considered his own.

Dirac was also renowned for his modesty. He called the equation for the time evolution of a quantum mechanical operator the "Heisenberg equation of motion" when he was the first to write it. When referring to the Fermi-Dirac statistics, he always insisted on saying Fermi statistics.

When he was once asked about poetry, he replied: «In science one tries to tell people, in a way that everyone can understand, something that no one ever knew before. Poetry is exactly the opposite.

When he visited the Soviet Union, he was invited to a conference in the philosophy of physics. He simply stood up and wrote on the blackboard: "Physical laws must have the simplicity and beauty of mathematics." This concept of mathematical beauty, even before experimental evidence became available, guided virtually his entire scientific career. Because of his frequent trips to the Soviet Union, he was prevented from entering the United States for some time.

Dirac was an acknowledged atheist. After speaking with Dirac, Pauli said in his chronicles: "If I understand Dirac correctly, he says: there is no God, and Dirac is his prophet."

Dirac, although for several years he showed himself to be an atheist, over time in 1963 declared for an article in Scientific American that he considers God to be a great mathematician who used advanced science to create the universe. At a lecture in 1971 he was skeptical that life arose by chance, saying that "God must be assumed to exist" in relation to the laws of quantum physics.

He maintained political positions relatively leaning to the left, although not militant. He often visited the Soviet Union and was close friends with the Soviet physicist Pyotr Kapitsa. Although he participated in the theoretical development of nuclear energy and in engineering developments for uranium enrichment, during World War II he remained practically outside of research for the development of nuclear weapons.

Legacy

Dirac is widely considered one of the greatest physicists of all time. He was one of the founders of quantum mechanics and quantum electrodynamics, being considered by some physicists as the most relevant physicist of the XX century .

His early contributions include the modern calculus of operators for quantum mechanics, which he called the Theory of Transformations, as well as an early version of the path integral formulation. He also created a many-body formalism for quantum mechanics that allowed each particle to have its own time.

His relativistic wave equation for the electron was the first successful statement of relativistic quantum mechanics. Dirac founded quantum field theory with his interpretation of the Dirac equation as a many-body equation, with which he predicted the existence of antimatter as well as the annihilation processes of matter and antimatter. Likewise, he was the first to formulate quantum electrodynamics, although he could not calculate arbitrary quantities due to the short distance limit that renormalization requires.