View source for Louis de Broglie

{{Short description|French physicist and aristocrat (1892–1987)}}
{{Redirect|de Broglie|other members of the family|House of Broglie|the asteroid|30883 de Broglie}}
{{more citations needed|date=August 2019}}
{{Use dmy dates|date=June 2016}}
{{Infobox scientist
| honorific_prefix  = [[Duke]]
| honorific_suffix  = {{post-nominals|country=GBR|size=100%|ForMemRS}}
| image             = Broglie Big.jpg
| caption           = De Broglie in 1929
| birth_name        = Louis Victor Pierre Raymond
| birth_date        = {{birth date|df=yes|1892|8|15}}
| birth_place       = [[Dieppe]], [[Normandy (administrative region)|Normandy]], [[French Third Republic]]
| death_date        = {{death date and age|df=y|1987|3|19|1892|8|15}}
| death_place       = [[Louveciennes]], [[Île-de-France]], France
| alma_mater        = [[University of Paris]] ([[PhD]], 1924)
| known_for         = {{plainlist|
*{{nowrap|Postulating [[matter wave]]s (1924)}}
* Proposing the [[de Broglie–Bohm theory]] (1927)
}}
| relatives         = [[Maurice de Broglie, 6th Duke of Broglie]] (brother)
| family            = [[House of Broglie|Broglie]]
| awards            = {{plainlist|
*[[Nobel Prize in Physics]] (1929)
*[[Max Planck Medal]] (1938)
*[[Kalinga Prize]] (1952)
*[[Fellow of the Royal Society#Foreign member|ForMemRS]] (1953)
}}
| honors            = [[File:Legion of Honour - Grand Cross (France).png|25px]] Grand Cross of the [[Legion of Honour]] (1961)
| fields            = {{tree list}}
*[[Physics]]
**[[Quantum mechanics]]
{{tree list/end}}
| work_institutions = University of Paris 
| thesis_title      = Recherches sur la théorie des quanta (Research on quanta theory)
| thesis_url        = https://tel.archives-ouvertes.fr/tel-00006807
| thesis_year       = 1924
| doctoral_advisor  = [[Paul Langevin]]
| doctoral_students = {{ubl|[[Bernard d'Espagnat]]|[[Cécile DeWitt-Morette]]|[[Alexandru Proca]]|[[Mioara Mugur-Schächter]]|[[Marie-Antoinette Tonnelat]]|[[Jean-Pierre Vigier]]}}
}}
{{Scholia}}

'''Louis Victor Pierre Raymond, 7th Duc de Broglie''' ({{IPAc-en|d|ə|_|ˈ|b|r|oʊ|ɡ|l|i}},<ref>{{Cite dictionary |url=http://www.lexico.com/definition/de+Broglie,+Louis-Victor |archive-url=https://web.archive.org/web/20201204231723/https://www.lexico.com/definition/de_broglie,_louis-victor |url-status=dead |archive-date=2020-12-04 |title=de Broglie, Louis-Victor |dictionary=[[Lexico]] UK English Dictionary |publisher=[[Oxford University Press]]}}</ref> <small>also</small> {{IPAc-en|US|d|ə|_|b|r|oʊ|ˈ|ɡ|l|iː|,_|d|ə|_|ˈ|b|r|ɔɪ}};<ref>{{Cite American Heritage Dictionary|de Broglie|access-date=10 August 2019}}</ref><ref>{{cite web|url=https://www.collinsdictionary.com/dictionary/english/de-broglie|title=De Broglie|work=[[Collins English Dictionary]]|publisher=[[HarperCollins]]|access-date=10 August 2019}}</ref> {{IPA|fr|də bʁɔj|lang}}<ref>{{cite book |author=Léon Warnant |title=Dictionnaire de la prononciation française dans sa norme actuelle |edition=3rd |year=1987 |publisher=J. Duculot, S. A. |location=Gembloux |language=fr |isbn=978-2-8011-0581-8 }}</ref><ref>{{cite book |author=Jean-Marie Pierret |title=Phonétique historique du français et notions de phonétique générale |year=1994 |publisher=Peeters |location=Louvain-la-Neuve |language=fr |isbn=978-9-0683-1608-7 |page=102}}</ref> <small>or</small> {{IPA|fr|də bʁœj||De Broglie.ogg}}; 15 August 1892 – 19 March 1987)<ref name=louveciennes /> was a French [[physicist]] and [[aristocrat]] known for his contributions to [[Old quantum theory|quantum theory]]. In his 1924 PhD thesis, he postulated the wave nature of [[electron]]s and suggested that [[Matter wave|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 in Physics]] in 1929, after the wave-like behaviour of matter was [[Davisson–Germer experiment|first experimentally demonstrated]] in 1927.

The wave-like behaviour of particles discovered by de Broglie was used by [[Erwin Schrödinger]] in his formulation of [[Schrödinger equation|wave mechanics]].<ref>{{Cite book |last=Whittaker |first=Edmund T. |title=A history of the theories of aether & electricity. 2: The modern theories, 1900 - 1926 |date=1989 |publisher=Dover Publ |isbn=978-0-486-26126-3 |edition=Repr |location=New York}}</ref>{{rp|270}}
De Broglie's [[pilot-wave]] concept,<ref name="PhD-thesis">Antony Valentini: ''On the Pilot-Wave Theory of Classical, Quantum and Subquantum Physics'', Ph.D. Thesis, ISAS, Trieste 1992</ref> was presented at the 1927 [[Solvay Conference]]s then abandoned, in favor of the [[quantum mechanics]], until 1952 when it was [[De Broglie–Bohm theory|rediscovered and enhanced by David Bohm]].<ref>{{Cite web|url = http://www.yoga6d.org/debroglie_vs_bohm/  |publisher=Excerpts from 1960 book published by Elsevier Pub.Co. | access-date=30 June 2015|title = de Broglie vs Bohm}}</ref>

Louis de Broglie was the sixteenth member elected to occupy [[List of members of the Académie française#Seat 1|seat 1]] of the [[Académie française]] in 1944, and served as Perpetual Secretary of the [[French Academy of Sciences]].<ref>{{MacTutor Biography|id=Broglie}}</ref><ref>{{cite web | title=History of International Academy of Quantum Molecular Science | url=http://www.iaqms.org/history.php | publisher=IAQMS | access-date=2010-03-08}}</ref> De Broglie became the first high-level scientist to call for establishment of a multi-national laboratory, a proposal that led to the establishment of the European Organization for Nuclear Research ([[CERN]]).<ref>{{Cite web|url = http://www.nndb.com/people/313/000072097/  |publisher=Soylent Communications | access-date=12 June 2015|title = Louis de Broglie}}</ref>

== Biography ==

=== Family and education ===
[[File:Portrait of François Marie de Broglie, Duke of Broglie, Marshal of France (member of the circle of Hyacinthe Rigaud).jpg|thumb|[[François-Marie, 1st duc de Broglie]] (1671–1745) ancestor of Louis de Broglie and [[Marshal of France]] under [[Louis XV of France]]]]

Louis de Broglie belonged to the famous aristocratic family of [[House of Broglie|Broglie]], whose representatives for several centuries occupied important military and political posts in France. The father of the future physicist, [[Victor, 5th duc de Broglie|Louis-Alphonse-Victor, 5th duc de Broglie]], was married to Pauline d’Armaille, the granddaughter of the Napoleonic General [[Philippe Paul, comte de Ségur]] and his wife, the biographer, [[Marie Célestine Amélie d'Armaillé]]. They had five children; in addition to Louis, these were: Albertina (1872–1946), subsequently the Marquise de Luppé; [[Maurice de Broglie|Maurice]] (1875–1960), subsequently a famous experimental physicist; Philip (1881–1890), who died two years before the birth of Louis, and Pauline, Comtesse de Pange (1888–1972), subsequently a famous writer.<ref name="Nye">{{cite journal |author = M. J. Nye. |title= Aristocratic Culture and the Pursuit of Science: The De Broglies in Modern France |journal= Isis|edition= Isis  |year= 1997 |volume= 88 |issue=  3|pages = 397–421 |doi =  10.1086/383768|jstor= 236150|s2cid= 143439041}}</ref> 

Louis was born in [[Dieppe, France|Dieppe]], Seine-Maritime. As the youngest child in the family, Louis grew up in relative loneliness, read a lot, and was fond of history, especially political. From early childhood, he had a good memory and could accurately read an excerpt from a theatrical production or give a complete list of ministers of the [[Third Republic of France]]. For this, he was predicted to become a great statesman in the future.<ref name="Abragam">{{cite journal |author = [[Anatole Abragam|A. Abragam]]. |title= Louis Victor Pierre Raymond de Broglie |edition= Biographical Memoirs of Fellows of the Royal Society  |year= 1988 |volume= 34 |pages = 22–41 |doi =  10.1098/rsbm.1988.0002|doi-access=  }}</ref>

De Broglie had intended a career in [[humanities]], and received his first degree (''[[Licentiate (degree)#France|licence ès lettres]]'') in history. Afterwards he turned his attention toward mathematics and physics and received a degree (''[[Licentiate (degree)#France|licence ès sciences]]'') 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.

=== Military service ===

After graduation, Louis de Broglie joined the engineering forces to undergo compulsory service. It began at [[Fort Mont Valérien]], but soon, on the initiative of his brother, he was seconded to the Wireless Communications Service and worked on the [[Eiffel Tower]], where the radio transmitter was located. Louis de Broglie remained in military service throughout the First World War, dealing with purely technical issues. In particular, together with [[Léon Brillouin]] and brother Maurice, he participated in establishing wireless communications with submarines. Louis de Broglie was demobilized in August 1919 with the rank of [[adjudant]]. Later, the scientist regretted that he had to spend about six years away from the fundamental problems of science that interested him.<ref name="Abragam" /><ref name="Dict">{{cite journal |author = J. Lacki. |url= http://www.encyclopedia.com/doc/1G2-2830905527.html |title= Louis de Broglie |edition= New Dictionary of Scientific Biography  |location= Detroit |year= 2008 |publisher= Charles Scribner's Sons |volume= 1 |pages = 409–415 }}</ref>

=== Scientific and pedagogical career ===
His 1924 thesis ''Recherches sur la théorie des quanta''<ref name="De_Broglie_PhD_English">{{cite web |last1=de Broglie |first1=Louis Victor |title=On the Theory of Quanta |url=http://aflb.ensmp.fr/LDB-oeuvres/De_Broglie_Kracklauer.pdf |website=Foundation of Louis de Broglie |edition= English translation by A.F. Kracklauer, 2004. |access-date=2 January 2020}}</ref> (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 [[Matter wave|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). He won the [[Nobel Prize in Physics]] in 1929 "for his discovery of the wave nature of electrons".<ref>{{cite web |title=The Nobel Prize in Physics 1929 |publisher=Nobel Foundation |url=http://nobelprize.org/nobel_prizes/physics/laureates/1929/index.html |access-date=9 October 2008 |archive-url=https://web.archive.org/web/20081024052522/http://nobelprize.org/nobel_prizes/physics/laureates/1929/index.html |archive-date=24 October 2008 |url-status=live }}</ref>

In his later career, de Broglie worked to develop a [[causality (physics)|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. In 1930 he founded the book series Actualités scientifiques et industrielles published by [[Éditions Hermann]].<ref>[https://www.sudoc.fr/01331081X Recherche (PPN) 01331081X: Actualités scientifiques et industrielles], sudoc.fr. Retrieved 11 December 2021.</ref>

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 non-religious.<ref>{{cite book|title=Quantum Mechanics at the Crossroads: New Perspectives From History, Philosophy And Physics|year=2007|publisher=Springer|isbn=9783540326632|first1=James |last1=Evans |first2=Alan S. |last2=Thorndike|page=71|quote=Asked to join Le Conseil de l'Union Catholique des Scientifiques<!-- the source has "Sceintifiques", but that is a typo --> Français, Louis declined because, he said, he had ceased the religious practices of his youth.}}</ref><ref>Kimball, John (2015). Physics Curiosities, Oddities, and Novelties. CRC Press. p. 323. {{ISBN|978-1-4665-7636-0}}.</ref>
In 1941, he was made a member of the National Council of [[Vichy France]].<ref> Les professeurs de la Faculté des sciences de Paris [https://www.persee.fr/doc/inrp_0298-5632_1989_ant_25_1_8664]</ref> 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.

Louis became the 7th [[duc de Broglie]] in 1960 upon the death without heir of his elder brother, [[Maurice, 6th duc de Broglie]], also a physicist.

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.<ref name="PiecuchMaruani2009">{{cite book|author1=Piotr Piecuch|author2=Jean Maruani|author3=Gerardo Delgado-Barrio|author4=Stephen Wilson|title=Advances in the Theory of Atomic and Molecular Systems: Conceptual and Computational Advances in Quantum Chemistry|url=https://books.google.com/books?id=1qbgc17K1dAC|date=30 September 2009|publisher=Springer Science & Business Media|isbn=978-90-481-2596-8|page=4}}</ref>

Louis never married. When he died on 19 March 1987 in [[Louveciennes]] at the age of 94,<ref name=louveciennes>{{cite book |title=A Century of Nobel Prize Recipients: Chemistry, Physics, and Medicine |edition=illustrated |first1=Francis |last1=Leroy |publisher=CRC Press |year=2003 |isbn=0-8247-0876-8 |page=141 |url=https://books.google.com/books?id=8DjwaFWE4fYC}} [https://books.google.com/books?id=8DjwaFWE4fYC&pg=PA141 Extract of page 141]</ref> he was succeeded as [[duke]] by a distant cousin, [[Victor-François, 8th duc de Broglie]]. His funeral was held 23 March 1987 at the Church of Saint-Pierre-de-Neuilly.<ref name="NéelBroglie1988">{{cite book |author1=Louis Néel |url=https://books.google.com/books?id=C0u4AAAAIAAJ |title=Louis de Broglie que nous avons connu |author2=Fondation Louis de Broglie |author3=Conservatoire national des arts et métiers (France) |publisher=Fondation Louis de Broglie, Conservatoire national des arts et métiers |year=1988}}</ref>

== Scientific activity ==
{{more citations needed section|date=June 2015}}

=== Physics of X-ray and photoelectric effect ===
The first works of Louis de Broglie (early 1920s) were performed in the laboratory of his [[Maurice de Broglie|older brother Maurice]] and dealt with the features of the [[photoelectric effect]] and the properties of [[x-rays]]. These publications examined the absorption of X-rays and described this phenomenon using the [[Bohr theory]], applied quantum principles to the interpretation of [[Photoemission spectroscopy|photoelectron spectra]], and gave a systematic classification of X-ray spectra.<ref name="Abragam" /> The studies of X-ray spectra were important for elucidating the structure of the internal electron shells of atoms (optical spectra are determined by the outer shells). Thus, the results of experiments conducted together with Alexandre Dauvillier, revealed the shortcomings of the existing schemes for the distribution of electrons in atoms; these difficulties were eliminated by [[Edmund Stoner]].<ref>''The Philosophy of Quantum Mechanics: The Interpretations of Quantum Mechanics in Historical Perspective''. New York: Wiley-Interscience, 1974. {{ISBN|0-471-43958-4}}</ref> Another result was the elucidation of the insufficiency of the Sommerfeld formula for determining the position of lines in X-ray spectra; this discrepancy was eliminated after the discovery of the electron spin. In 1925 and 1926, Leningrad physicist [[Orest Khvolson]] nominated the de Broglie brothers for the Nobel Prize for their work in the field of X-rays.<ref name="Nye" />

=== Matter and wave–particle duality ===
{{Main|De Broglie hypothesis}}
Studying the nature of X-ray radiation and discussing its properties with his brother Maurice, who considered these rays to be some kind of combination of waves and particles, contributed to Louis de Broglie's awareness of the need to build a theory linking particle and wave representations. In addition, he was familiar with the works (1919–1922) of [[Marcel Brillouin]], which proposed a hydrodynamic model of an atom and attempted to relate it to the results of Bohr's theory. The starting point in the work of Louis de Broglie was the idea of Einstein about the [[Photon|quanta of light]]. In his first article on this subject, published in 1922, the French scientist considered blackbody radiation as a gas of light quanta and, using classical statistical mechanics, derived the [[Wien approximation|Wien radiation law]] in the framework of such a representation. In his next publication, he tried to reconcile the concept of light quanta with the phenomena of interference and diffraction and came to the conclusion that it was necessary to associate a certain periodicity with quanta. In this case, light quanta were interpreted by him as relativistic particles of very small mass.<ref name="Mehra">{{cite journal |author = J. Mehra. |editor= J. Mehra. |title= Louis de Broglie and the phase waves associated with matter |edition= The Golden Age of Theoretical Physics  |year= 2001 |publisher= World Scientific |pages = 546–570 }}</ref>

It remained to extend the wave considerations to any massive particles, and in the summer of 1923 a decisive breakthrough occurred. De Broglie outlined his ideas in a short note "Waves and quanta" ({{langx|fr|Ondes et quanta}}, presented at a meeting of the Paris Academy of Sciences on September 10, 1923),<ref>{{Cite web |date=1923 |title=Membres de l'Académie des sciences depuis sa création: Louis de Broglie Ondes et quanta |language=fr |url=https://www.academie-sciences.fr/pdf/dossiers/Broglie/Broglie_pdf/CR1923_p507.pdf |website=academie-sciences.fr}}</ref> which marked the beginning of the creation of wave mechanics. In this paper and his subsequent PhD thesis,<ref name="De_Broglie_PhD_English"></ref> the scientist suggested that a moving particle with energy ''E'' and velocity '''v''' is characterized by some internal periodic process with a frequency <math>E/h</math> (later known as [[Compton frequency]]), where <math>h</math> is the [[Planck constant]]. To reconcile these considerations, based on the quantum principle, with the ideas of special relativity, de Broglie associated wave he called a "phase wave" with a moving body, which propagates with the [[phase velocity]] <math>c^2/v</math>. Such a wave, which later received the name [[matter wave]], or [[de Broglie wave]], in the process of body movement remains in phase with the internal periodic process. Having then examined the motion of an electron in a closed orbit, the scientist showed that the requirement for phase matching directly leads to the quantum [[Bohr-Sommerfeld quantization|Bohr-Sommerfeld condition]], that is, to quantize the angular momentum. In the next two notes (reported at the meetings on September 24 and October 8, respectively), de Broglie came to the conclusion that the particle velocity is equal to the [[group velocity]] of phase waves, and the particle moves along the normal to surfaces of equal phase. In the general case, the trajectory of a particle can be determined using [[Fermat's principle]] (for waves) or the [[principle of least action]] (for particles), which indicates a connection between geometric optics and classical mechanics.<ref>[[Max Jammer]] ''The Conceptual Development of Quantum Mechanics''. New York: McGraw-Hill, 1966 2nd ed: New York: American Institute of Physics, 1989. {{ISBN|0-88318-617-9}}. Olivier Darrigol, "Strangeness and soundness in Louis de Broglie's early works", ''Physis'',  30 (1993): 303–372.</ref>

This theory set the basis of wave mechanics. It was supported by Einstein, confirmed by the [[Davisson–Germer experiment|electron diffraction experiments]] of G P Thomson and Davisson and Germer, and generalized by the work of Erwin Schrödinger.

From a philosophical viewpoint, this theory of matter-waves 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 matter-waves, following the work of [[David Bohm]].

=== Conjecture of an internal clock of the electron <span class="anchor" id="de Broglie internal clock"></span> ===
[[File:Solvay conference 1927 (group photograph) with frame.jpg|thumb|de Broglie presented at the Solvay conference 1927 (third from right in middle row)]]
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.<ref>See for example the description of de Broglie's view in: David Bohm, Basil Hiley: ''The de Broglie pilot wave theory and the further development and new insights arising out of it'', Foundations of Physics, volume 12, number 10, 1982, Appendix: On the background of the papers on trajectories interpretation, by D. Bohm, ([http://leopard.physics.ucdavis.edu/rts/p298/pilotwavetheory.pdf PDF] {{webarchive|url=https://web.archive.org/web/20110819234038/http://leopard.physics.ucdavis.edu/rts/p298/pilotwavetheory.pdf |date=19 August 2011 }})</ref> Subsequently, [[David Hestenes]] has proposed a link to the [[zitterbewegung]] that was suggested by Schrödinger.<ref>D. Hestenes, October 1990, The Zitterbewegung interpretation of quantum mechanics, Foundations of Physics, vol.&nbsp;20, no.&nbsp;10, pp.&nbsp;1213–1232</ref>

While attempts at verifying the internal clock hypothesis and measuring clock frequency are so far not conclusive,<ref>See for example G.R. Osche, ''Electron channeling resonance and de Broglie's internal clock'', Annales de la Fondation Louis de Broglie, vol.&nbsp;36, 2001, pp.&nbsp;61–71 ([http://aflb.ensmp.fr/AFLB-361/aflb361m718.pdf full text])</ref> recent experimental data is at least compatible with de Broglie's conjecture.<ref>Catillon, Foundations of Physics, July 2001, vol.&nbsp;38, no.&nbsp;7, pp.&nbsp;659–664</ref>

=== Non-nullity and variability of mass ===
According to de Broglie, the [[neutrino]] and the [[photon]] have rest masses that are non-zero, 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.

=== Generalization of the principle of least action ===
{{ Also| Hamilton's optico-mechanical analogy}}
In the second part of his 1924 thesis, de Broglie used the equivalence of the mechanical principle of least action with [[Fermat's principle|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 latter equivalence had been pointed out by [[William Rowan Hamilton]] a century earlier, and published by him around 1830, for the case of light.

=== Duality of the laws of nature ===
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 [[Natural law|laws of nature.]]

His last work made a single system of laws from the two large systems of thermodynamics and of mechanics:{{cn|date=December 2023}}
{{blockquote|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 [[Gottfried Wilhelm Leibniz]], who posited the necessity of "architectonic principles" to complete the system of mechanical laws.{{cn|date=December 2023}}

However, according to him, there is less duality, in the sense of opposition, than synthesis (one is the limit of the other){{cn|date=December 2023}} 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:
: <math> m c^2 = h \nu </math>

=== Neutrino theory of light ===
{{main|Neutrino theory of light}}
This theory, which dates from 1934, introduces the idea that the photon is equivalent to the fusion of two [[Dirac fermion|Dirac neutrino]]s.<ref>{{Cite journal |last=Pryce |first=Maurice Henry Lecorney |last2=null |first2=null |last3=Dirac |first3=Paul Adrien Maurice |last4=null |first4=null |date=1997 |title=On the neutrino theory of light |url=https://royalsocietypublishing.org/doi/10.1098/rspa.1938.0058 |journal=Proceedings of the Royal Society of London. Series A. Mathematical and Physical Sciences |volume=165 |issue=921 |pages=247–271 |doi=10.1098/rspa.1938.0058}}</ref> In 1938, the concept was challenged as not rotationally invariant and work on the concept was largedly discontinued.<ref>{{Cite journal |last=Perkins |first=W. A. |date=1965 |title=Neutrino Theory of Photons |url=https://journals.aps.org/pr/abstract/10.1103/PhysRev.137.B1291 |journal=Physical Review |volume=137 |issue=5B |pages=B1291–B1301 |doi=10.1103/PhysRev.137.B1291}}</ref>

=== Hidden thermodynamics ===
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's theorem (thermodynamics)|Carnot]].

In this work, [[Action (physics)|action]] becomes a sort of opposite to [[entropy]], through an equation that relates the only two universal dimensions of the form:
: <math>{\text{action}\over h} = -{\text{entropy}\over k}</math>
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''.

== Honors and awards ==
* 1929 [[Nobel Prize in Physics]]
* 1929 [[Poincaré Medal|Henri Poincaré Medal]]
* 1932 [[Albert I of Monaco]] Prize
* 1938 [[Max Planck Medal]]
* 1938 Fellow, [[Royal Swedish Academy of Sciences]]
* 1939 International Member, [[American Philosophical Society]]<ref>{{Cite web |title=APS Member History |url=https://search.amphilsoc.org/memhist/search?creator=Louis+de+Broglie&title=&subject=&subdiv=&mem=&year=&year-max=&dead=&keyword=&smode=advanced |access-date=2023-05-10 |website=search.amphilsoc.org}}</ref>
* 1944 Fellow, [[Académie française]]
* 1948 International Member, United States [[National Academy of Sciences]]<ref>{{Cite web |title=Duc L. De Broglie |url=http://www.nasonline.org/member-directory/deceased-members/46723.html |access-date=2023-05-10 |website=www.nasonline.org}}</ref>
* 1952 [[Kalinga Prize]]
* 1953 Fellow, [[Royal Society]]<ref name="frs">{{Cite journal | last1 = Abragam | first1 = A. | author-link = Anatole Abragam| doi = 10.1098/rsbm.1988.0002 | title = Louis Victor Pierre Raymond de Broglie. 15 August 1892-19 March 1987 | journal = [[Biographical Memoirs of Fellows of the Royal Society]] | volume = 34 | pages = 22–26 | year = 1988 | jstor = 770045| doi-access =  }}</ref>
* 1958 International Honorary Member of the [[American Academy of Arts and Sciences]]<ref>{{Cite web |title=Louis Victor Pierre Raymond de Broglie |url=https://www.amacad.org/person/louis-victor-pierre-raymond-de-broglie |access-date=2023-05-10 |website=American Academy of Arts & Sciences |date=9 February 2023 |language=en}}</ref>

== Publications ==
[[File:Broglie, Louis de – Ondes et mouvements, 1926 – BEIC 3903635.jpg|thumb|''Ondes et mouvements'', 1926]]

* ''Recherches sur la théorie des quanta'' (''Researches on the quantum theory''), Thesis, Paris, 1924, Ann. de Physique (10) '''3''', 22 (1925).
* ''Introduction à la physique des rayons X et gamma'' (''Introduction to physics of X-rays and Gamma-rays''), with [[Maurice de Broglie]], Gauthier-Villars, 1928.
* {{Cite book|title=Ondes et mouvements|volume=|publisher=Gauthier-Villars|location=Paris|year=1926|language=fr|url=https://gutenberg.beic.it/webclient/DeliveryManager?pid=3903635}}
* ''Rapport au 5ème Conseil de Physique Solvay'' (''Report for the 5th Solvay Physics Congress''), Brussels, 1927.
* {{Cite book|title=Mecanique ondulatoire|volume=|publisher=Gauthier-Villars|location=Paris|year=1928|language=fr|url=https://gutenberg.beic.it/webclient/DeliveryManager?pid=3937499}}
* {{Cite book|title=Recueil d'exposés sur les ondes et corpuscules|volume=|publisher=Librairie scientifique Hermann et C.ie|location=Paris|year=1930|language=fr|url=https://gutenberg.beic.it/webclient/DeliveryManager?pid=3898660}}
* ''Matière et lumière'' (''Matter and Light''), Paris: Albin Michel, 1937.
* ''La Physique nouvelle et les quanta'' (''New Physics and Quanta''), Flammarion, 1937.
* ''Continu et discontinu en physique moderne'' (''Continuous and discontinuous in Modern Physics''), Paris: Albin Michel, 1941.
* ''Ondes, corpuscules, mécanique ondulatoire'' (''Waves, Corpuscles, Wave Mechanics''), Paris: Albin Michel, 1945.
* ''Physique et microphysique'' (''Physics and Microphysics''), Albin Michel, 1947.
* ''Vie et œuvre de Paul Langevin'' (''The life and works of [[Paul Langevin]]''), French Academy of Sciences, 1947.
* ''Optique électronique et corpusculaire'' (''Electronic and Corpuscular Optics''), Herman, 1950.
* ''Savants et découvertes'' (''Scientists and discoveries''), Paris, Albin Michel, 1951.
* ''Une tentative d'interprétation causale et non linéaire de la mécanique ondulatoire: la théorie de la double solution''. Paris: Gauthier-Villars, 1956.
** English translation: ''Non-linear Wave Mechanics: A Causal Interpretation''. Amsterdam: Elsevier, 1960.
* ''Nouvelles perspectives en microphysique'' (''New prospects in Microphysics''), Albin Michel, 1956.
* ''Sur les sentiers de la science'' (''On the Paths of Science''), Paris: Albin Michel, 1960.
* ''Introduction à la nouvelle théorie des particules de M. [[Jean-Pierre Vigier]] et de ses collaborateurs'', Paris: Gauthier-Villars, 1961. Paris: Albin Michel, 1960.
** English translation: ''Introduction to the Vigier Theory of elementary particles'', Amsterdam: Elsevier, 1963.
* ''Étude critique des bases de l'interprétation actuelle de la mécanique ondulatoire'', Paris: Gauthier-Villars, 1963.
** English translation: ''The Current Interpretation of Wave Mechanics: A Critical Study'', Amsterdam, Elsevier, 1964.
* ''Certitudes et incertitudes de la science'' (''Certitudes and Incertitudes of Science''). Paris: Albin Michel, 1966.
* with Louis Armand, Pierre Henri Simon and others. ''[[Albert Einstein]]''. Paris: Hachette, 1966.
** English translation: ''Einstein''. Peebles Press, 1979.<ref>{{cite journal|title=Review of ''Einstein'' by Louis de Broglie and others|journal=Bulletin of the Atomic Scientists|date=March 1980|volume=36|issue=3|pages=50|url=https://books.google.com/books?id=ZAoAAAAAMBAJ&pg=PA50}}</ref>
* ''Recherches d'un demi-siècle'' (''Research of a half-century''), Albin Michel, 1976.
* ''Les incertitudes d'Heisenberg et l'interprétation probabiliste de la mécanique ondulatoire'' (''[[Werner Heisenberg|Heisenberg]] uncertainty and wave mechanics probabilistic interpretation''), Gauthier-Villars, 1982.

== References ==
{{reflist}}

== External links ==
{{commons}}
{{Wikiquotepar|Louis de Broglie}}
* [https://web.archive.org/web/20041212175715/http://www.academie-francaise.fr/immortels/base/academiciens/fiche.asp?param=580 Les Immortels: Louis de BROGLIE]", Académie française {{in lang|fr}}
* {{Nobelprize}}
* [http://aflb.ensmp.fr/ Fondation Louis de Broglie]
* {{MathGenealogy|id=105807}}
* [http://neo-classical-physics.info/uploads/3/0/6/5/3065888/de_broglie_-_hidden_thermodynamics_book.pdf  English translation of his book on hidden thermodynamics by D. H. Delphenich]
* [http://neo-classical-physics.info/uploads/3/0/6/5/3065888/de_broglie_-_measurement_in_wave_mechanics.pdf The Theory of measurement in wave mechanics] (English translation of his book on the subject)
* [http://neo-classical-physics.info/uploads/3/0/6/5/3065888/de_broglie_-_new_conception_of_light.pdf "A new conception of light"] (English translation)
* [http://www.ina.fr/video/AFE04002106 Louis de Broglie Interview], on Ina.fr {{in lang|fr}}
* {{PM20}}

{{S-start}}
{{S-reg|fr}}
{{S-bef|before=[[Maurice de Broglie]]}}
{{S-ttl|title=[[House of Broglie|Duke of Broglie]]|years=1960–1987}}
{{S-aft|after=[[Victor-François, 8th duc de Broglie|Victor-François de Broglie]]}}
{{S-end}}

{{Nobel Prize in Physics Laureates 1926–1950}}
{{1929 Nobel Prize winners}}
{{Académie française Seat 1}}
{{Dukes of Broglie}}

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{{DEFAULTSORT:Broglie, Louis De}}
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[[Category:Foreign members of the USSR Academy of Sciences]]
[[Category:Foreign fellows of the Indian National Science Academy]]
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[[Category:Members of the International Academy of Quantum Molecular Science]]
[[Category:French military personnel of World War I]]
[[Category:Nobel laureates in Physics]]
[[Category:French Nobel laureates]]
[[Category:Kalinga Prize recipients]]
[[Category:Grand Cross of the Legion of Honour]]
[[Category:Winners of the Max Planck Medal]]