Anti-de Sitter space bell. It might be described as being the "opposite" of the surface of a sphere, which has a positive curvature. General relativity is a theory of the nature of time, space and gravity in which gravity is a curvature of space and time that results from the presence of matter or energy. Energy and mass are equivalent (as expressed in the equation "E" = "mc"), and space and time can be translated into equivalent units based on the speed of light ("c" in the "E" = "mc" equation). A common analogy involves the way that a dip in a flat
Lane–Emden equation series solution: This leads to a recursive relationship for the expansion coefficients: This relation can be solved leading to the general solution: The boundary condition for a physical polytrope demands that formula_67 as formula_68. This requires that formula_69, thus leading to the solution: We start from with the Lane–Emden equation: Rewriting for formula_72 produces: Differentiating with respect to "ξ" leads to: Reduced, we come by: Therefore, the Lane–Emden equation has the solution when formula_77. This solution is finite in mass but infinite in radial extent, and therefore the complete polytrope does not represent a physical solution. Chandrasekhar believed for a