Louis Victor Pierre Raymond de Broglie, duc de Broglie (/dəˈbrɔɪ/; French: [dəbʁɔj]^{[1]}^{[2]} or [dəbʁœj] (listen); 15 August 1892 – 19 March 1987)^{[3]} was a French physicist who made groundbreaking contributions to quantum theory. In his 1924 PhD thesis, he postulated the wave nature of electrons and suggested that all matter has wave properties. This concept is known as the de Broglie hypothesis, an example of wave–particle duality, and forms a central part of the theory of quantum mechanics.
De Broglie won the Nobel Prize for Physics in 1929, after the wavelike behaviour of matter was first experimentally demonstrated in 1927.
The 1925 pilotwave model,^{[4]} and the wavelike behaviour of particles discovered by de Broglie was used by Erwin Schrödinger in his formulation of wave mechanics.^{[5]} The pilotwave model and interpretation was then abandoned, in favor of the quantum formalism, until 1952 when it was rediscovered and enhanced by David Bohm.^{[6]}
Louis de Broglie was the sixteenth member elected to occupy seat 1 of the Académie française in 1944, and served as Perpetual Secretary of the French Academy of Sciences.^{[7]}^{[8]} De Broglie became the first highlevel scientist to call for establishment of a multinational laboratory, a proposal that led to the establishment of the European Organization for Nuclear Research (CERN).^{[9]}
Louis de Broglie  

Born  15 August 1892 Dieppe, France 
Died  19 March 1987 (aged 94) Louveciennes, France 
Nationality  French 
Alma mater  University of Paris (ΒΑ in History, 1910; BA in Sciences, 1913; PhD in physics, 1924) 
Known for  Wave nature of electrons De Broglie–Bohm theory de Broglie wavelength 
Awards  Nobel Prize in Physics (1929) Henri Poincaré Medal (1929) Albert I of Monaco Prize (1932) Max Planck Medal (1938) Kalinga Prize (1952) 
Scientific career  
Fields  Physics 
Institutions  University of Paris (Sorbonne) 
Thesis  Recherches sur la théorie des quanta("Research on Quantum Theory") (1924) 
Doctoral advisor  Paul Langevin 
Doctoral students  Cécile DeWittMorette Bernard d'Espagnat JeanPierre Vigier Alexandru Proca MarieAntoinette Tonnelat 
Louis de Broglie was born to a noble family in Dieppe, SeineMaritime, younger son of Victor, 5th duc de Broglie. He became the 7th duc de Broglie in 1960 upon the death without heir of his older brother, Maurice, 6th duc de Broglie, also a physicist. He never married. When he died in Louveciennes,^{[3]} he was succeeded as duke by a distant cousin, VictorFrançois, 8th duc de Broglie.
De Broglie had intended a career in humanities, and received his first degree in history. Afterwards he turned his attention toward mathematics and physics and received a degree in physics. With the outbreak of the First World War in 1914, he offered his services to the army in the development of radio communications.
His 1924 thesis Recherches sur la théorie des quanta (Research on the Theory of the Quanta) introduced his theory of electron waves. This included the wave–particle duality theory of matter, based on the work of Max Planck and Albert Einstein on light. This research culminated in the de Broglie hypothesis stating that any moving particle or object had an associated wave. De Broglie thus created a new field in physics, the mécanique ondulatoire, or wave mechanics, uniting the physics of energy (wave) and matter (particle). For this he won the Nobel Prize in Physics in 1929.
In his later career, de Broglie worked to develop a causal explanation of wave mechanics, in opposition to the wholly probabilistic models which dominate quantum mechanical theory; it was refined by David Bohm in the 1950s. The theory has since been known as the De Broglie–Bohm theory.
In addition to strictly scientific work, de Broglie thought and wrote about the philosophy of science, including the value of modern scientific discoveries.
De Broglie became a member of the Académie des sciences in 1933, and was the academy's perpetual secretary from 1942. He was asked to join Le Conseil de l'Union Catholique des Scientifiques Francais, but declined because he was nonreligious and an atheist.^{[10]}^{[11]} On 12 October 1944, he was elected to the Académie française, replacing mathematician Émile Picard. Because of the deaths and imprisonments of Académie members during the occupation and other effects of the war, the Académie was unable to meet the quorum of twenty members for his election; due to the exceptional circumstances, however, his unanimous election by the seventeen members present was accepted. In an event unique in the history of the Académie, he was received as a member by his own brother Maurice, who had been elected in 1934. UNESCO awarded him the first Kalinga Prize in 1952 for his work in popularizing scientific knowledge, and he was elected a Foreign Member of the Royal Society on 23 April 1953.^{[12]}
In 1961, he received the title of Knight of the Grand Cross in the Légion d'honneur. De Broglie was awarded a post as counselor to the French High Commission of Atomic Energy in 1945 for his efforts to bring industry and science closer together. He established a center for applied mechanics at the Henri Poincaré Institute, where research into optics, cybernetics, and atomic energy were carried out. He inspired the formation of the International Academy of Quantum Molecular Science and was an early member.^{[13]} His funeral was held 23 March 1987 at the Church of SaintPierredeNeuilly.^{[14]}
"The fundamental idea of [my 1924 thesis] was the following: The fact that, following Einstein's introduction of photons in light waves, one knew that light contains particles which are concentrations of energy incorporated into the wave, suggests that all particles, like the electron, must be transported by a wave into which it is incorporated... My essential idea was to extend to all particles the coexistence of waves and particles discovered by Einstein in 1905 in the case of light and photons." "With every particle of matter with mass m and velocity v a real wave must be 'associated'", related to the momentum by the equation:
where is the wavelength, is the Planck constant, is the momentum, is the rest mass, is the velocity and is the speed of light in a vacuum."
This theory set the basis of wave mechanics. It was supported by Einstein, confirmed by the electron diffraction experiments of G P Thomson and Davisson and Germer, and generalized by the work of Schrödinger.
However, this generalization was statistical and was not approved of by de Broglie, who said "that the particle must be the seat of an internal periodic movement and that it must move in a wave in order to remain in phase with it was ignored by the actual physicists [who are] wrong to consider a wave propagation without localization of the particle, which was quite contrary to my original ideas."
From a philosophical viewpoint, this theory of matterwaves has contributed greatly to the ruin of the atomism of the past. Originally, de Broglie thought that real wave (i.e., having a direct physical interpretation) was associated with particles. In fact, the wave aspect of matter was formalized by a wavefunction defined by the Schrödinger equation, which is a pure mathematical entity having a probabilistic interpretation, without the support of real physical elements. This wavefunction gives an appearance of wave behavior to matter, without making real physical waves appear. However, until the end of his life de Broglie returned to a direct and real physical interpretation of matterwaves, following the work of David Bohm. The de Broglie–Bohm theory is today the only interpretation giving real status to matterwaves and representing the predictions of quantum theory.
In his 1924 thesis, de Broglie conjectured that the electron has an internal clock that constitutes part of the mechanism by which a pilot wave guides a particle.^{[15]} Subsequently David Hestenes has proposed a link to the Zitterbewegung that was suggested by Erwin Schrödinger.^{[16]}
While attempts at verifying the internal clock hypothesis and measuring clock frequency are so far not conclusive,^{[17]} recent experimental data is at least compatible with de Broglie's conjecture.^{[18]}
According to de Broglie, the neutrino and the photon have rest masses that are nonzero, though very low. That a photon is not quite massless is imposed by the coherence of his theory. Incidentally, this rejection of the hypothesis of a massless photon enabled him to doubt the hypothesis of the expansion of the universe.
In addition, he believed that the true mass of particles is not constant, but variable, and that each particle can be represented as a thermodynamic machine equivalent to a cyclic integral of action.
In the second part of his 1924 thesis, de Broglie used the equivalence of the mechanical principle of least action with Fermat's optical principle: "Fermat's principle applied to phase waves is identical to Maupertuis' principle applied to the moving body; the possible dynamic trajectories of the moving body are identical to the possible rays of the wave." This equivalence had been pointed out by Hamilton a century earlier, and published by him around 1830, in an era where no experience gave proof of the fundamental principles of physics being involved in the description of atomic phenomena.
Up to his final work, he appeared to be the physicist who most sought that dimension of action which Max Planck, at the beginning of the 20th century, had shown to be the only universal unity (with his dimension of entropy).
Far from claiming to make "the contradiction disappear" which Max Born thought could be achieved with a statistical approach, de Broglie extended wave–particle duality to all particles (and to crystals which revealed the effects of diffraction) and extended the principle of duality to the laws of nature.
His last work made a single system of laws from the two large systems of thermodynamics and of mechanics:
When Boltzmann and his continuators developed their statistical interpretation of Thermodynamics, one could have considered Thermodynamics to be a complicated branch of Dynamics. But, with my actual ideas, it's Dynamics that appear to be a simplified branch of Thermodynamics. I think that, of all the ideas that I've introduced in quantum theory in these past years, it's that idea that is, by far, the most important and the most profound.
That idea seems to match the continuous–discontinuous duality, since its dynamics could be the limit of its thermodynamics when transitions to continuous limits are postulated. It is also close to that of Leibniz, who posited the necessity of "architectonic principles" to complete the system of mechanical laws.
However, according to him, there is less duality, in the sense of opposition, than synthesis (one is the limit of the other) and the effort of synthesis is constant according to him, like in his first formula, in which the first member pertains to mechanics and the second to optics:
This theory, which dates from 1934, introduces the idea that the photon is equivalent to the fusion of two Dirac neutrinos.
It shows that the movement of the center of gravity of these two particles obeys the Maxwell equations—that implies that the neutrino and the photon both have rest masses that are nonzero, though very low.
De Broglie's final idea was the hidden thermodynamics of isolated particles. It is an attempt to bring together the three furthest principles of physics: the principles of Fermat, Maupertuis, and Carnot.
In this work, action becomes a sort of opposite to entropy, through an equation that relates the only two universal dimensions of the form:
As a consequence of its great impact, this theory brings back the uncertainty principle to distances around extrema of action, distances corresponding to reductions in entropy.
Asked to join Le Conseil de l'Union Catholique des Scientifiques Français, Louis declined because, he said, he had ceased the religious practices of his youth.
French nobility  

Preceded by Maurice de Broglie 
Duke of Broglie 1960–1987 
Succeeded by VictorFrançois de Broglie 
The year 1924 in science and technology involved some significant events, listed below.
Arnold PomeransArnold Julius Pomerans (27 April 1920 – 30 May 2005) was a Germanborn British translator.Arnold Pomerans was born in Königsberg, Germany on 27 April 1920 to a Jewish family. Because of growing antisemitism in Germany the family left for Yugoslavia and later South Africa. In 1948 Arnold Pomerans emigrated to England, where he became a fulltime translator in the 1950s after first working as a teacher. He translated about two hundred works of fiction and nonfiction, selected from most European languages. Among the authors he translated are Louis de Broglie, Anne Frank, Sigmund Freud, Johan Huizinga, Jean Piaget, Jacques Presser and Jan Romein. His translation of George Grosz's autobiography A Little Yes and a Big No earned him the 1983 SchlegelTieck Prize and in 1997 he was awarded the PEN Translation Prize for The Selected Letters of Vincent Van Gogh. In his obituary he was called "one of Britain's finest translators" by The Independent.In 1956 he married Erica White and they moved to Polstead in Suffolk the following year. They carried out much of the translation work together. He died in Polstead of cancer on 30 May 2005, aged 85.
Davisson–Germer experimentThe Davisson–Germer experiment was a 19237 experiment by Clinton Davisson and Lester Germer at Western Electric (later Bell Labs), in which electrons, scattered by the surface of a crystal of nickel metal, displayed a diffraction pattern. This confirmed the hypothesis, advanced by Louis de Broglie in 1924, of waveparticle duality, and was an experimental milestone in the creation of quantum mechanics.
Fereydoon MotamedFereydoon Motamed (also known as Amir Fereydoun Motamed, Amir Fereydoon Motamed or Fereydoon H. Motamed), (1917 born in Tehran, Iran – 1993 death in Charlottesville, Virginia), was an internationally known professor and linguist, winner of the Louis de Broglie award, from the Académie française, and recipient of literary award "Le Grand Prix Littéraire d'Iran" from Writer's Association of French Language.
Fondation LouisdeBroglieThe Fondation LouisdeBroglie is a French foundation for research into physics. The foundation is located at the French Academy of Sciences in Paris.
Foundations of PhysicsFoundations of Physics is a monthly journal "devoted to the conceptual bases and fundamental theories of modern physics and cosmology, emphasizing the logical, methodological, and philosophical premises of modern physical theories and procedures". The journal publishes results and observations based on fundamental questions from all fields of physics, including: quantum mechanics, quantum field theory, special relativity, general relativity, string theory, Mtheory, cosmology, thermodynamics, statistical physics, and quantum gravity
Foundations of Physics has been published since 1970. Its founding editors were Henry Margenau and Wolfgang Yourgrau. The 1999 Nobel laureate Gerard 't Hooft was editorinchief from January 2007. At that stage, it absorbed the associated journal for shorter submissions Foundations of Physics Letters, which had been edited by Alwyn Van der Merwe since its foundation in 1988. Past editorial board members (which include several Nobel laureates) include Louis de Broglie, Robert H. Dicke, Murray GellMann, Abdus Salam, Ilya Prigogine and Nathan Rosen. Carlo Rovelli was announced as new editorinchief in February 2016.
Franco SelleriFranco Selleri (Bologna, Italy, 9 October 1936 – 20 November 2013) was an Italian theoretical physicist and professor at the Università degli Studi di Bari Aldo Moro. He received his Doctorate / Ph.D. cum laude at the Università di Bologna in 1958, and was a fellow of the Istituto Nazionale di Fisica Nucleare beginning 1959. He was a member of the New York Academy of Sciences and the Fondation Louis de Broglie, and served on the Board of Directors of the Italian Physical Society.
He was well known for his analysis of the foundations of relativity theory and quantum mechanics. Several solutions have been proposed for the paradoxes pointed out by him. Philosophically, his position was that of a realist. He was in close contact with Karl Popper who, though very old, took part in a conference on the subject that Selleri organized in 1985 in Bari.He had numerous visiting professorships and fellowships, including CERN, Saclay, University of Nebraska, Cornell University, and Dubna. Also, he was the recipient of a medal from Gdanskie Towarzystwo Naukowe (Poland). During his scientific career, he published more than 200 papers in particle physics, quantum theory, relativity and history and philosophy of physics. He was the author of numerous books and editor of numerous conference proceedings on topics relating to the foundations of physics.
Georges LochakGeorges Lochak is a French physicist known for his work on magnetic monopoles.
International Academy of Quantum Molecular ScienceThe International Academy of Quantum Molecular Science (IAQMS) is an international scientific learned society covering all applications of quantum theory to chemistry and chemical physics. It was created in Menton in 1967. The founding members were Raymond Daudel, PerOlov Löwdin, Robert G. Parr, John Pople and Bernard Pullman. Its foundation was supported by Louis de Broglie.Originally the Academy had 25 regular members under 65 years of age. This was later raised to 30, and then to 35. There is no limit on the number of members over 65 years of age. The members are "chosen among the scientists of all countries who have distinguished themselves by the value of their scientific work, their role of pioneer or leader of a school in the broad field of quantum chemistry, i.e. the application of quantum mechanics to the study of molecules and macromolecules". The Academy presently consists of 90 members (as of 2006). The Academy organizes the International Congress of Quantum Chemistry every three years.
The academy awards a medal to a young member of the scientific community who has distinguished himself or herself by a pioneering and important contribution. The award has been made every year since 1967.
JeanPierre VigierJeanPierre Vigier (January 16, 1920, Paris – May 4, 2004, Paris) was a theoretical physicist, known for his work on the foundations of physics, and in particular on his stochastic interpretation of quantum physics.
Jean RobieuxJean Robieux (15 October 1925 – 14 June 2012) was a French physicist. A graduate from École Polytechnique and Doctor of Science, he is a leading French specialist in laser and optronics.
He is the former scientific director of the Research Center of Alcatel Mobile Phones at Marcoussis, and during many years, head of the Robotics college at the École centrale Paris. He is a chairman of the board of directors of the school and chairman of the Scientific Council. He followed in particular the development the materials department. He suggested the initial creation of the ECAM Rennes  Louis de Broglie school in 1988.
Kalinga PrizeThe Kalinga Prize for the Popularization of Science is an award given by UNESCO for exceptional skill in presenting scientific ideas to lay people. It was created in 1952, following a donation from Biju Patnaik, Founder President of the Kalinga Foundation Trust in India.
MarieAntoinette TonnelatMarieAntoinette Tonnelat (née Baudot) (March 5, 1912 – December 3, 1980) was a French theoretical physicist. She received her doctorate in 1939 under the supervision of Louis de Broglie. She is best known for her work related to Albert Einstein's Theory of Relativity. Her research focused on synthesizing the concepts gravity, electromagnetism, and nuclear forces within the basic framework provided by Einstein's theory of relativity. Along with the help of Einstein and Schrödinger, she played a role in developing Unified Field Theory.
Matter waveMatter waves are a central part of the theory of quantum mechanics, being an example of wave–particle duality. All matter can exhibit wavelike behavior. For example, a beam of electrons can be diffracted just like a beam of light or a water wave. The concept that matter behaves like a wave was proposed by Louis de Broglie (/dəˈbrɔɪ/) in 1924. It is also referred to as the de Broglie hypothesis. Matter waves are referred to as de Broglie waves.
The de Broglie wavelength is the wavelength, λ, associated with a massive particle and is related to its momentum, p, through the Planck constant, h:
Wavelike behavior of matter was first experimentally demonstrated by George Paget Thomson's thin metal diffraction experiment, and independently in the Davisson–Germer experiment both using electrons, and it has also been confirmed for other elementary particles, neutral atoms and even molecules.
Maurice de BroglieLouisCésarVictorMaurice, 6th duc de Broglie (27 April 1875 – 14 July 1960) was a French physicist. Brother of the theoretical physicist, Louis de Broglie.
Mioara MugurSchächterMioara MugurSchächter is a French physicist of Romanian origin, a specialist in quantum physics and epistemology.
Olivier Costa de BeauregardOlivier Costa de Beauregard (Paris, 6 November 1911 – Poitiers, 5 February 2007) was a French relativistic and quantum physicist, and philosopher of science. He was an eminent specialist of time and of information theory. He studied under Louis de Broglie.
From 1947, he proposed to de Broglie his interpretation of the EPR paradox which questions the notion of time. In 1974, with Bernard d'Espagnat, he suggested to Christian Imbert, a young professor at Institut d'Optique, to propose to Alain Aspect to perform a Bell's inequalities experimental test, to settle the conflict between the results of Clauser and Freedman at Berkeley, and Holt and Pipkin at Harvard. After Aspect decided to do a different experiment, he explained the quantum mechanical predictions by the theory of retrocausation or CPTinvariance.
His numerous publications also concerned the inertial effect of spin, the Imbert effect, Fresnel evanescent wave of Fresnel, and Dirac equation.
Pilot wave theoryIn theoretical physics, the pilot wave theory, also known as Bohmian mechanics, was the first known example of a hiddenvariable theory, presented by Louis de Broglie in 1927.
Its more modern version, the de Broglie–Bohm theory, interprets quantum mechanics as a deterministic theory, avoiding troublesome notions such as wave–particle duality, instantaneous wave function collapse, and the paradox of Schrödinger's cat. To solve these problems, the theory is inherently nonlocal and nonrelativistic.
The de Broglie–Bohm pilot wave theory is one of several interpretations of (nonrelativistic) quantum mechanics.
An extension to the relativistic case has been developed since the 1990s.
Robert ValléeRobert Vallée (5 October 1922 in Poitiers, France – 1 January 2017, Paris, France) was a French cyberneticist and mathematician. He was Professor at the Paris 13 University (University of ParisNord) and president of the World Organization of Systems and Cybernetics (WOSC),.At the beginning of the 1950s, Vallée wrote his first publications on what he named "opérateur d'observation" (which means in English "operator of observation"). The latter, in the simplest case, allows a cybernetic system to observe the state of its environment and itself. Thereafter, on the basis of these results, a decisional operator will be able to indicate the action to be taken. The two stages of perception and decision are distinguished by "intellectual convenience", but it is interesting to gather them in a unique operator, known as "pragmatic". A decision is influenced by the observation of events, but also by past perceptions. That means that, in the observation made at a given moment, traces of past observations are also present. Eventually, these processes follow one another in a loop. Vallée defined the study of this situation with the term "epistemopraxeology", underlining the existing link between knowledge (episteme), resulting from observation, and action (praxis). Regarding the observation problem, Vallée was also interested in information theory.
Vallée also nourished private interests in sociological problems as well as in history. The first led him to describe a cybernetic creature covering the whole surface of the globe with its communication net (1952), an idea which has also been proposed (under the name of "cybionte", 1975) by Joël de Rosnay. He also wrote articles devoted to historical aspects of cybernetics and systems, referring to René Descartes, Louis de Broglie, and Norbert Wiener.


This page is based on a Wikipedia article written by authors
(here).
Text is available under the CC BYSA 3.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.