Andrew Strominger of Harvard University presents his work on soft algebras, the symmetry structures that govern the behavior of gauge and gravitational fields at infinity, across three different spacetime backgrounds: flat Minkowski space and the curved anti-de Sitter and de Sitter geometries AdS4 and dS4. Recorded at the MPG-IAS-NTU Center Kick-off Conference at the Institute for Advanced Study's Wolfensohn Hall, the talk traces how the celestial holography program, built on soft theorems and asymptotic symmetries in flat space, extends or changes when the cosmological constant is turned on. Strominger lays out the algebraic structures found so far, compares their behavior across the three settings, and points to open problems in extending holographic duality beyond the flat-space case. The talk assumes familiarity with gauge theory and general relativity and runs just under fifty minutes.