'''Ali H. Chamseddine''' is a [[Lebanon|Lebanese]]<ref>[http://users.ictp.it/~sci_info/News_from_ICTP/News_98/features_CAMS.html "Math for Peace"]. News from ICTP, No. 98, Autumn 2001</ref> physicist known for his contributions to [[particle physics]], [[general relativity]] and [[mathematical physics]].<ref name="Rivasseau2007">{{cite book|author=Vincent Rivasseau|title=Quantum Spaces: Poincaré Seminar 2007|url=http://books.google.com/books?id=kLaFht4FCdwC&pg=PA25|date=22 December 2007|publisher=Springer London, Limited|isbn=978-3-7643-8522-4|pages=25–}}</ref><ref name="ConnesMarcolli">{{cite book|author1=Alain Connes|author2=Matilde Marcolli|title=Noncommutative Geometry, Quantum Fields and Motives|url=http://books.google.com/books?id=a6PdFik-a9QC&pg=PR15|publisher=American Mathematical Soc.|isbn=978-0-8218-7478-3|pages=15–}}</ref> {{as of|2013}}, Chamseddine is a physics Professor at the [[American University of Beirut]] and [[Institut des Hautes Études Scientifiques]].

Chamseddine's research revolves around non-commutative geometry in particle physics as well as supergravity theory.<ref>http://th-workshop2011.desy.de/sites/site_th-workshop2011/content/e98837/e98838/e124244/infoboxContent124245/Chamseddine.pdf</ref>

He is perhaps best known for the construction of a realistic model of particle interactions within the N = 1 supergravity framework where supersymmetry (SUSY) is broken by a super Higgs mechanism, carried out by Ali Chamseddine, [[Richard Arnowitt]] and [[Pran Nath]] in 1982.<ref>http://journals.aps.org/prl/pdf/10.1103/PhysRevLett.49.970</ref><ref>Themes in Unification: The Pran Nath Festschrift" PASCOS 2004, Editors George Alverson and [[Michael Vaughn]], World Scientific 2005</ref> In these classes of models collectively now known as minimal supergravity Grand Unification Theories (mSUGRA GUT), gravity mediates the breaking of SUSY through the existence of a hidden sector.<ref>[http://cerncourier.com/cws/article/cern/28918 "mSUGRA celebrates its 20th year".] ''Cern Courier'', 4 September 2003.</ref>

Chamseddine frequently works with cited Fields Medalist [[Alain Connes]] on non-commutative geometry.<ref name="docs.google">https://docs.google.com/file/d/0B8tITtoqQkxfRXh4X0ZmeUlXLTQ/edit?pli=1</ref> One of the work done between the two is the so-called "Spectral [[Action (physics)|Action Principle]]". In this paper, Chamseddine and Connes propose a new action principle to be associated with a non-commutative space (A, H, D). The universal formula for the spectral action is (ψ, Dψ) + [[Trace (linear algebra)|Trace]](χ(D/Λ)) where ψ is a [[spinor]] on the [[Hilbert space]], Λ is a scale and χ a positive function. When this principle is applied to the non-commutative space defined by the spectrum of the standard model, one obtains the standard model action coupled to Einstein plus Weyl gravity. There are relations between the gauge coupling constants identical to those of SU(5) as well as the Higgs self-coupling, to be taken at a fixed high energy scale.<ref>http://download.springer.com/static/pdf/875/art%253A10.1007%252Fs002200050126.pdf?auth66=1414176544_9481d67e0d4a5591ecdf4bcda0c64592&ext=.pdf</ref> Moreover, on August 2013, Chamseddine and [[Viatcheslav Mukhanov]] proposed a new model to describe the effect of [[Dark Matter]], the model is called "Mimetic Dark Matter". In this model, Chamseddine and Mukhanov represented the effect of dark matter as a purely geometrical one coming from splitting the [[Differential geometry|metric]] of [[spacetime]] into an auxiliary metric, which keeps the physical metric invariant under [[Conformal map|conformal transformations]], and the derivative of a scalar field φ. After solving for the equations of motion, a tensor that resembles the [[Energy-momentum tensor|Stress-Energy tensor]] of dust comes out of the equations, even in the absence of normal matter. This tensor represents the effect of Cold Dark Matter. The results are published in <ref name="Mimetic Dark Metter">http://arxiv.org/pdf/1308.5410v1.pdf</ref> and in <ref name="Cosmology With Mimetic Dark Matter">http://arxiv.org/pdf/1403.3961v2.pdf</ref>