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  "body": "\n## Summary\n\nA harmonic map is a smooth map between [[Riemannian manifolds|7CBT4SM83Y]] that is a critical point of the energy.\nThe energy is the integral of the squared size of the differential.\nHarmonic maps include [[harmonic functions|0DEB0JMN0W]], [[geodesics|NSYMQMHPDN]], isometries and holomorphic maps between Kähler manifolds.\nThey satisfy a nonlinear elliptic system and are a central object of geometric analysis.\n\n## Explanations\n\n### L1 human\n\nThink of a rubber sheet $M$ stretched over a curved surface $N$.\nThe energy measures how much the sheet is stretched.\nA harmonic map is a position of the sheet in equilibrium, where small changes do not change the stretching to first order.\nA map from a circle that runs along a great circle of a sphere at constant speed is a harmonic map.\n",
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