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 P: 243 I am as newbie as they get when it comes to string theory. But, as far as I know open and closed strings differ by the boundary conditions imposed on the string function $X^\mu(\sigma,\tau)$. The Dirichlet boundary conditions are imposed so that the endpoints do not "move" (e.g, the string ties two very heavy quarks). The Neumann boundary conditions allow movement (e.g, the string ties two light quarks). I fail to see how transforming one type into another would allow us to apper in other dimensions.