{{Short description|French physicist (1923–1999)}} '''Louis Michel''' ({{IPA|fr|lwi miʃɛl}}; 1923–1999) was a French mathematical physicist at the Institut des Hautes Études Scientifiques (IHÉS).<ref>{{cite web |last=Cipra |first=Barry Arthur |author-link=Barry Arthur Cipra |date=8 January 1998 |title=A Gem of a Definition |url=http://www.siam.org/news/news.php?id=809 |work=Scientific American |access-date=2007-11-19 |archive-url=https://web.archive.org/web/20110517050238/http://www.siam.org/news/news.php?id=809 |archive-date=17 May 2011 |url-status=dead }}</ref> He was born in Roanne, in the Loire department in central France, on 4 May 1923, and died in Bures-sur-Yvette (Essonne), in the Île-de-France region, on 30 December 1999. His name is associated with Michel parameters describing the phase space distribution of leptonic decays of charged leptons, the Bargmann–Michel–Telegdi equation describing spin evolution in a magnetic field,<ref> {{cite journal |last1=Bargman |first1=V. |last2=Michel |first2=L. |last3=Telegdi |first3=V. |year=1959 |title=Precession of the Polarization of Particles Moving in a Homogeneous Electromagnetic Field |journal=Physical Review Letters |volume=2 |issue=10 |pages=435 |bibcode=1959PhRvL...2..435B |doi=10.1103/PhysRevLett.2.435}}</ref> and the Michel–Radicati theory for the SU(3) octet,<ref> {{cite journal |last1=Michel |first1=L. |last2=Radicati |first2=L. |year=1971 |title=Properties of the breaking of hadronic internal symmetry |journal=Annals of Physics |volume=66 |issue=2 |pages=758 |bibcode=1971AnPhy..66..758M |doi=10.1016/0003-4916(71)90079-0}}</ref><ref> {{cite journal |last1=Michel |first1=L. |last2=Radicati |first2=L. |year=1973 |title=The geometry of the octet |url=http://archive.numdam.org/article/AIHPA_1973__18_3_185_0.pdf |journal=Annales de l'Institut Henri Poincaré A |volume=18 |pages=185 |mr=325036 |zbl=0267.22019}}</ref>
==Biography==
Michel completed his studies at the École Polytechnique in Paris. After World War II, he went to Manchester, England, where he worked on weak interactions. Back in France, he was teaching in Lille and Orsay before creating the ''Centre de Physique Théorique of the École Polytechnique'' (CPHT) in Palaiseau. In 1962, he became a permanent professor at ''Institut des Hautes Études Scientifiques'' (IHÉS) in Bures-sur-Yvette, where he remained until his retirement, and as an emeritus professor until his death.
Louis Michel was President of the Société Française de Physique between 1978 and 1980, and a member of the French Academy of Sciences since 1979. In 1982, he was awarded the Wigner Medal.
His scientific activities in the domain of theoretical physics encompassed many fields, from elementary particles and high energy physics to crystals, and provided pioneering insights in spontaneous symmetry breaking in many contexts. Including a theory of phase transitions as a symmetry-breaking,<ref> {{cite journal |last1=Michel |first1=L. |year=1953 |title=Selection rules imposed by charge conjugation |journal=Il Nuovo Cimento |volume=10 |issue=3 |pages=319–339 |bibcode=1953NCim...10..319M |doi=10.1007/BF02786202 |s2cid=122834949}}</ref> his geometric theory of spontaneous symmetry breaking,<ref> {{cite journal |last1=Michel |first1=L. |year=1971 |title=Points critiques des fonctions invariantes sur une G-variété |url=http://public.ihes.fr/LouisMichel/publications/CRAS.272_433_1971.pdf |journal=Comptes Rendus de l'Académie des Sciences de Paris |volume=272 |pages=433}}</ref><ref> {{cite journal |last1=Michel |first1=L. |year=1980 |title=Symmetry defects and broken symmetry. Configurations Hidden Symmetry |journal=Reviews of Modern Physics |volume=52 |issue=3 |pages=618 |bibcode=1980RvMP...52..617M |doi=10.1103/RevModPhys.52.617}}</ref><ref name="six"> {{cite journal |last1=Michel |first1=L. |last2=Kim |first2=J. S. |last3=Zak |first3=J. |last4=Zhilinskii |first4=B. |year=2001 |title=Symmetry, invariants, topology |journal=Physics Reports |volume=341 |issue=1–6 |pages=7–9 |bibcode=2001PhR...341....7M |doi=10.1016/S0370-1573(00)00087-9}}</ref> and to several results in crystallography.<ref name="six" />
He supervised Claude Bouchiat on the first calculations on the influence of hadron pairs on the anomalous magnetic moment of the muon.<ref>{{Cite web|date=2008|title=CV Claude Bouchiat|url=https://www.academie-sciences.fr/pdf/membre/BouchiatC_bio1008.pdf|access-date=24 July 2021|website=Académie de Sciences}}</ref><ref>{{Cite journal|last1=Bouchiat|first1=Claude|last2=Michel|first2=Louis|date=1961|title=La résonance dans la diffusion méson π— méson π et le moment magnétique anormal du méson μ|url=http://www.edpsciences.org/10.1051/jphysrad:01961002202012101|journal=Journal de Physique et le Radium|volume=22|issue=2|pages=121|doi=10.1051/jphysrad:01961002202012101|issn=0368-3842}}</ref>
In 2000, in honor of his memory, the IHÉS created the ''chaire Louis Michel de physique théorique'', an academic chair for distinguished long-term visitors.<ref>{{Cite web | url=http://smf4.emath.fr/en/Publications/Gazette/2018/156/smf_gazette_156_23-28.pdf |title = Les Publications | Société Mathématique de France}}</ref>
==References== {{reflist}}
==Further reading== *{{cite journal |last1=Kim |first1=J. S. |last2=Zak |first2=J. |last3=Zhilinskii |first3=B. |year=2001 |title=Obituary |journal=Physics Reports |volume=341 |issue= 1–6|pages=5–6 |bibcode= 2001PhR...341....5K |doi=10.1016/S0370-1573(00)00086-7 }} {{Authority control}}
{{DEFAULTSORT:Michel, Louis}} Category:Members of the French Academy of Sciences Category:1923 births Category:1999 deaths Category:People from Roanne Category:Institute for Advanced Study visiting scholars Category:French mathematical physicists Category:20th-century French mathematicians Category:Presidents of the Société Française de Physique Category:20th-century French physicists