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
Nonlinear Schrödinger equation Starting from the trivial solution "U" = 0 and iterating, one obtains the solutions with "n" solitons. The NLS equation is a partial differential equation like the Gross-Pitaevskii equation. Usually it does not have analytic solution and the same numerical methods used to solve the Gross-Pitaevskii equation, such as the split-step Crank–Nicolson and Fourier spectral methods, are used for its solution. There are different Fortran and C programs for its solution. The nonlinear Schrödinger equation is Galilean invariant in the following sense: Given a solution "ψ"("x, t") a new solution can be obtained by replacing "x" with "x" + "vt"