Paul Adrien Maurice Dirac is a Physicien and British Mathématicien born the August 8th 1902 with Bristol and deceased the October 20th 1984 with Tallahassee, Florida (the United States).

There is one of the fathers of the quantum Mécanique and remains famous to have envisaged the existence of the Antimatière (Positron).

Biography

His/her father, Charles Dirac, are originating in Suisse, in the Canton of Were worth. It is established with Bristol and Marie with Florence Holten with which it will have three children, Paul being the junior. Its paternal family is resulting from the town of Dirac in Charentes.

He studies mathematics at the university of his birthplace and enters starting from 1923 to the university of Cambridge. In 1925, it meets Niels Bohr, then Werner Heisenberg. There it publishes its first article this year on the formalism of traditional and quantum physics. In 1926, it shows the physical equivalence of the Wave mechanics of Erwin Schrödinger and the model of Heisenberg. It supports its thesis this same year and share to work with Bohr in Copenhagen. It joined Göttingen in 1927. In September, it is invited to the fifth Congrès Solvay where it meets Albert Einstein.

In 1928, it deduces from the work of Pauli on a system of Spin S not-relativist a relativistic equation describing the electron, and containing in oneself the spin. It is called today equation of Dirac. That makes it possible Dirac to predict in 1931 the existence of a particle called Positron, the Antiparticule of the electron. 1932 will have to be awaited so that Anderson and Blackett observes finally this particle.

In the principles of quantum mechanics , published in English 1930, it uses the algebra of the linear operators like a generalization of the theories of Heisenberg and Schrödinger. It thus introduces the Notation bra-ket, for which $\backslash \; left|\; \backslash \; psi\; \backslash \; right\; \backslash \; rangle$ is a vector of state in the space of the states of the system, and $\backslash \; left\; \backslash \; langle\; \backslash \; psi\; \backslash \; right|$ a vector of the dual Space corresponding.

It divides the Nobel Prize of physics in 1933 with Erwin Schrödinger for “ the discovery of new and productive forms of the atomic Théorie ”. It Marie one year later with Margit Wigner with which he will have two girls.

Dirac was “Professor Lucasien” at the university of Cambridge of 1932 with 1969, and professor of first cycle to the Université of Bristol-board. He is prize winner of the Royal Medal in 1939 and of the Médaille Copley in 1952. In 1970, it joined the University of Florida and settles in Tallahassee where it dies 14 years later.

For the needs for the quantum formalism, Dirac introduced a singular object, which one calls today impulse of Dirac or mass of Dirac , noted $\backslash \; delta\; (T)$. This impulse represents a signal of theoretically null duration and finished energy, and must check the condition:

$\backslash \; int\; \backslash \; delta\; (T)\; \backslash \; dt\; \backslash \; =\; \backslash \; 1$

This concept of impulse did not have a precise mathematical base: in particular, it could not be a question of a ordinary function , because a function which is null almost everywhere has an identically null integral, according to the theory of the integration of Lebesgue. The mathematician Laurent Schwartz invented the tools adequate to describe this kind of objects rigorously, the theory of the distributions.

Commonly, one says of a measurement which it is of Dirac if all the Densité is concentrated in a single point.

Its laconism and the puritanism of its behavior marked all its life.

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