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# Matrix Theory

Matrix theory is constructed in terms of N "points" (called "D0-branes"--for zero-dimensional membranes that act as Dirichlet boundaries for strings) which live in an eleven-dimensional spacetime. Their spatial positions are determined by the eigenvalues of nine N×N matrices, where N is eventually taken to infinity. The tenth dimension depends upon N, the number of points, and the page eleventh dimension is taken to lie on the light cone-- leaving only nine dimensions to be specified by matrix eigenvalues. This light-cone construction has its roots in the idea of Leonard Susskind, of Stanford University, and Gerard 't Hooft, of the University of Utrecht, in the Netherlands, that the three-dimensional space in which we live can be completely described by its two-dimensional boundary. Thus, the third dimension is not independent of the other two, and the world is, in a sense, a hologram.