general mechanisms string-fivebrane duality string-QFT duality QFT-QFT duality: effective QFT incarnations of open/closed string duality, relating (super-)gravity to (super-)Yang-Mills theory: Kramers-Wannier duality Seiberg duality (swapping NS5-branes) AGT correspondence (wrapped M5-branes) 3d-3d correspondence (wrapped M5-branes) What is called flat space holography is a – somewhat more hypothetical – generalization of the holographic principle in the form of the AdS-CFT correspondence, which should be applicable not to the usual bulk spacetimes that are asymptotically anti de Sitter, but to bulks that are asymptotically Minkowskian. In order to still relate this to branes notice that the far horizon geometry of all BPS branes is a flat orbifold spacetime (see there), but that “far” is Planck scale for single branes (“cone branes”), hence in the large 1/N limit (opposite to the large N limit in which the AdS-CFT correspondence applies). In one more well-developed version of flat space holography, scattering amplitudes in asymptotically flat spacetimes are related to conformal field theories on celestial spheres in two dimensions lower – “celestial amplitudes”. This goes back to an observation in de Boer & Solodukhin 2003. Early comments: (by the title, apparently originally intended to touch on AdS-QCD, but de facto ending with focus on the problem of flat space holography) Dedicated introduction and survey: Daniel Grumiller: Flat Space Holography, (2015) [pdf, pdf] Faïçal Barzi: Celestial Holography, A Hitchhiker’s Guide to the Celestial Sphere [arXiv:2608.07568] Activities: Original articles: Leonard Susskind, Holography in the flat space limit, AIP Conf.Proc. 493 (1999) 1, 98-112, (spire, arXiv:hep-th/9901079, doi:10.1063/1.1301570) (in relation to the BFSS matrix model) Jan de Boer, Sergey N. Solodukhin, A holographic reduction of Minkowski space-time, Nucl. Phys. B665 (2003) 545-593 (arXiv:hep-th/0303006) David Berenstein, A toy model for the AdS/CFT...