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\newtheorem{prop}{Proposition} \newtheorem{cor}{Corollary} \newtheorem*{utheorem}{Theorem} \newtheorem*{ulemma}{Lemma} \newtheorem*{uprop}{Proposition} \newtheorem*{ucor}{Corollary} \theoremstyle{definition} \newtheorem{defn}{Definition} \newtheorem{example}{Example} \newtheorem*{udefn}{Definition} \newtheorem*{uexample}{Example} \theoremstyle{remark} \newtheorem{remark}{Remark} \newtheorem{note}{Note} \newtheorem*{uremark}{Remark} \newtheorem*{unote}{Note} %------------------------------------------------------------------- \begin{document} %------------------------------------------------------------------- \section*{N=4 D=4 super Yang-Mills theory} \hypertarget{context}{}\subsubsection*{{Context}}\label{context} \hypertarget{physics}{}\paragraph*{{Physics}}\label{physics} [[!include physicscontents]] \hypertarget{quantum_field_theory}{}\paragraph*{{Quantum field theory}}\label{quantum_field_theory} [[!include functorial quantum field theory - contents]] \hypertarget{contents}{}\section*{{Contents}}\label{contents} \noindent\hyperlink{idea}{Idea}\dotfill \pageref*{idea} \linebreak \noindent\hyperlink{properties_of_4d_sym}{Properties of 4d SYM}\dotfill \pageref*{properties_of_4d_sym} \linebreak \noindent\hyperlink{conformal_invariance}{Conformal invariance}\dotfill \pageref*{conformal_invariance} \linebreak \noindent\hyperlink{ClosedExpressionsForPhysicalObservables}{Closed expressions for physical observables}\dotfill \pageref*{ClosedExpressionsForPhysicalObservables} \linebreak \noindent\hyperlink{holography_adscft}{Holography, AdS-CFT}\dotfill \pageref*{holography_adscft} \linebreak \noindent\hyperlink{twistor_space_formulation}{Twistor space formulation}\dotfill \pageref*{twistor_space_formulation} \linebreak \noindent\hyperlink{topological_twists}{Topological twists}\dotfill \pageref*{topological_twists} \linebreak \noindent\hyperlink{related_concepts}{Related concepts}\dotfill \pageref*{related_concepts} \linebreak \noindent\hyperlink{references}{References}\dotfill \pageref*{references} \linebreak \noindent\hyperlink{general}{General}\dotfill \pageref*{general} \linebreak \noindent\hyperlink{planar_sector_integrability_mhv_amplitudes}{Planar sector, integrability, MHV amplitudes}\dotfill \pageref*{planar_sector_integrability_mhv_amplitudes} \linebreak \noindent\hyperlink{ReferencesTwistorSpace}{Twistor space formulation}\dotfill \pageref*{ReferencesTwistorSpace} \linebreak \noindent\hyperlink{scattering_amplitudes}{Scattering amplitudes}\dotfill \pageref*{scattering_amplitudes} \linebreak \hypertarget{idea}{}\subsection*{{Idea}}\label{idea} The [[super Yang-Mills theory]] in [[dimension]] 4 with the maximum number $N = 4$ of [[supersymmetries]]. [[!include superconformal symmetry -- table]] \hypertarget{properties_of_4d_sym}{}\subsection*{{Properties of 4d SYM}}\label{properties_of_4d_sym} \hypertarget{conformal_invariance}{}\subsubsection*{{Conformal invariance}}\label{conformal_invariance} $N=4$ $D=4$ SYM is an [[SCFT]]. \hypertarget{ClosedExpressionsForPhysicalObservables}{}\subsubsection*{{Closed expressions for physical observables}}\label{ClosedExpressionsForPhysicalObservables} Among all [[gauge theory]] [[Lagrangians]] that of $N=4$, $D = 4$ SYM is special in several ways, in particular of course in that it is conformally invariant and in that it has maximal [[supersymmetry]]; and ultimately by the fact that it is the [[Kaluza-Klein mechanism|KK-reduction]] of the very special [[6d (2,0)-superconformal QFT]] and related by [[AdS-CFT|AdS7-CFT6 duality]] to the very special theory of [[11-dimensional supergravity]]/[[M-theory]]. Accordingly, it is to be expected that the [[quantum observables]] of $N=4$, $D = 4$ SYM satisfy special relations that make them more tractable than the observables of a generic [[gauge theory]], in particular by having closed-form expressions. Indeed, such relations have been and are being uncovered in the last years, in particular in what is called the \emph{[[planar limit]]} of the theory, where [[scattering amplitudes]] are dominated by [[Feynman diagrams]] that can be given the structure of planar [[graphs]]. This includes notably the following phenomena: \begin{enumerate}% \item The [[operator spectrum]] of the dilatation operator (the part of the [[stress-energy tensor]] which induces conformal transformations) can be expressed in closed form, indeed when regarded as a [[Hamiltonian]] it defines an [[integrable system]] equivalent to [[spin chain]] models. This has been used in particular to explicitly check aspects of the conjectured [[AdS-CFT duality]] of $N=4$, $D= 4$ SYM with [[type II string theory]] on [[anti de Sitter spacetimes]]. See the review (\hyperlink{Beisert}{Beisert et al}). \item Certain [[scattering amplitudes]] called \emph{maximally helicity violating amplitudes} (``[[MHV amplitudes]]'') simplify drastically as compared to the generic situation and in fact are controled by a certain [[twistor string theory]] whose [[target space]] is a [[twistor space]]. See (\hyperlink{Monteiro}{Monteiro}) for a review. \item Generally, the [[scattering amplitudes]] of the theory in the planar limit have certain closed-form combinatorial expressions. See (\hyperlink{Arkani-Hamed}{Arkani-Hamed et al}). \end{enumerate} Such ``exact solutions'' of the theory are of interest in that even though N=4, D=4 SYM is very different from [[phenomenology|phenomenologically viable]] models such that [[QCD]] in the [[standard model of particle physics]] in that it is highly (super-)symmetric and conformal, it is still similar enough (being a nonabelian [[gauge theory]] [[minimal coupling|minimally coupled]] to [[fermions]]) that one can or can hope to deduce from these exact results approximate information about these less symmetric theories. In other words, because understanding [[observables]] in [[QCD]]/[[Yang-Mills theory]] in general is difficult, going to special points in the space of all such theories -- such as the point of N=4, D=4 SYM -- may be hoped to yield a tractable approximation. For more on this way of studying [[QCD]] and other realistic theories by studying instead their highly symmetric but phenomenologically unrealistic siblings, see also at \emph{[[string theory results applied elsewhere]]}. \hypertarget{holography_adscft}{}\subsubsection*{{Holography, AdS-CFT}}\label{holography_adscft} $N=4$ $d=4$ SYM is supposed to be related under the [[AdS/CFT correspondence]] to [[type II superstring theory]] [[Kaluza-Klein mechanism|compactified]] on a 5-[[sphere]] to an asymptotically [[anti de Sitter spacetime]]. [[!include gauge theory from AdS-CFT -- table]] \hypertarget{twistor_space_formulation}{}\subsubsection*{{Twistor space formulation}}\label{twistor_space_formulation} There is a natural reformulation of the theory using [[twistor]] [[field (physics)|fields]]. See the references \hyperlink{ReferencesTwistorSpace}{below}. And see at \emph{[[twistor string theory]]}. \hypertarget{topological_twists}{}\subsubsection*{{Topological twists}}\label{topological_twists} There is a topological twist of 4d SYM to a [[TQFT]] -- the [[Kapustin-Witten TQFT]]. Its [[S-duality]] is supposed to contain [[geometric Langlands duality]] as a special case. See at \emph{[[topologically twisted D=4 super Yang-Mills theory]]}. \hypertarget{related_concepts}{}\subsection*{{Related concepts}}\label{related_concepts} \begin{itemize}% \item [[super Yang-Mills theory]] \item [[N=1 D=4 super Yang-Mills theory]] \item [[N=2 D=4 super Yang-Mills theory]] \item [[N=4 D=3 super Yang-Mills theory]] \item [[D=5 super Yang-Mills theory]] \item [[topologically twisted D=4 super Yang-Mills theory]] \end{itemize} [[!include table of branes]] \hypertarget{references}{}\subsection*{{References}}\label{references} \hypertarget{general}{}\subsubsection*{{General}}\label{general} An introduction to $d=4$ SYM is in \begin{itemize}% \item Joseph A. Minahan \emph{Review of AdS/CFT Integrability, Chapter I.1: Spin Chains in $N=4$ Super Yang-Mills} (\href{http://arxiv.org/abs/1012.3983}{arXiv:1012.3983}) \end{itemize} More recent results are in \begin{itemize}% \item Simon Caron-Huot, \emph{Superconformal symmetry and two-loop amplitudes in planar N=4 super Yang-Mills} (\href{http://arxiv.org/abs/1105.5606}{arXiv:1105.5606}) \end{itemize} Superconformal invariance of $N=4$, $D=4$ SYM can be shown with the result of \begin{itemize}% \item Robert Leigh, [[Matthew Strassler]], \emph{Exactly Marginal Operators and Duality in Four Dimensional N=1 Supersymmetric Gauge Theory} (\href{http://arxiv.org/abs/hep-th/9503121}{arXiv:hep-th/9503121}) \end{itemize} (after regarding it as $N=1$ SYM with three adjoint chiral [[superfield]]s). \hypertarget{planar_sector_integrability_mhv_amplitudes}{}\subsubsection*{{Planar sector, integrability, MHV amplitudes}}\label{planar_sector_integrability_mhv_amplitudes} A comprehensive discussion of the [[integrability]] related to anomalous dimension in the planar sector is in \begin{itemize}% \item N. Beisert et al., \emph{Review of AdS/CFT Integrability, An Overview} Lett. Math. Phys. vv, pp (2011), (\href{http://arxiv.org/abs/1012.3982}{arXiv:1012.3982}). \end{itemize} A review of [[MHV amplitudes]] is in \begin{itemize}% \item Gustavo Machado Monteiro, \emph{MHV Tree Amplitudes in Super-Yang-Mills and in Superstring Theory} (2010) (\href{http://www.ift.unesp.br/posgrad/gustavo.pdf}{pdf}) \end{itemize} Discussion of special properties of [[scattering amplitudes]] in the planar sector is in \begin{itemize}% \item [[Nima Arkani-Hamed]], Jacob L. Bourjaily, Freddy Cachazo, Alexander B. Goncharov, Alexander Postnikov, Jaroslav Trnka, \emph{Scattering Amplitudes and the Positive Grassmannian} (\href{http://arxiv.org/abs/1212.5605}{arXiv:1212.5605}) \end{itemize} For mathematical background see \begin{itemize}% \item Alexander Postnikov, \emph{Total positivity, Grassmannians, and networks} (\href{http://arxiv.org/abs/math/0609764}{arXiv:math/0609764}) \end{itemize} \hypertarget{ReferencesTwistorSpace}{}\subsection*{{Twistor space formulation}}\label{ReferencesTwistorSpace} The [[twistor]] space formulation of $N=4$ $D = 4$ SYM was originally found from the [[B-model]] [[string theory]] in \begin{itemize}% \item [[Edward Witten]], \emph{Perturbative Gauge Theory As A String Theory In Twistor Space}, Commun. Math. Phys. 252:189-258,2004 (\href{http://arxiv.org/abs/hep-th/0312171/}{arXiv:hep-th/0312171/}) \end{itemize} A comprehensive discussion is in \begin{itemize}% \item Rutger Boels, Lionel Mason, David Skinner, \emph{Supersymmetric Gauge Theories in Twistor Space}, JHEP 0702:014,2007 (\href{http://arxiv.org/abs/hep-th/0604040}{arXiv:hep-th/0604040}) \end{itemize} See also (\hyperlink{Monteiro}{Monteiro}) below. \hypertarget{scattering_amplitudes}{}\subsubsection*{{Scattering amplitudes}}\label{scattering_amplitudes} For the moment see at \begin{itemize}% \item \emph{[[scattering amplitude]]} \end{itemize} and also at \begin{itemize}% \item \emph{[[motivic multiple zeta values]]}. \end{itemize} [[!redirects N=4 D=4 SYM]] [[!redirects N=4 D=4 sYM]] [[!redirects D=4 N=4 SYM]] [[!redirects D=4 N=4 super Yang-Mills]] \end{document}