EntityQ864919· pop 14· linked from 66 articlesAlexandroff extensionSign in to savegiven a space X, the space X ⊔ {∞}, topologized so that a set containing ∞ is open iff its complement is closed compact in XConnectionszbMATH OpenEntityopen and closed mapsEntitymathematicsEntityInternational Standard Book NumberEntitytopologyEntitydigital object identifierEntitytopological spaceEntityhomeomorphismEntityPavel AleksandrovEntitycompact spaceEntityQ22908627EntityRiemann sphereEntityHausdorff spaceEntitylimit pointEntitySpringer Science+Business MediaEntitystereographic projectionEntityfunctorEntityisolated pointEntityEncyclopedia of MathematicsEntityMathematical ReviewsEntityCategoriesCompactification (mathematics)General topology