““Extending Polyakov's argument, he found evidence that the string theory describing those emergent strings is actually a ten-dimensional supersymmetric string theory. Of the nine dimensions of space in which these strings live, four of them are like the ones in Polyakov's conjecture. There are, then, five dimensions left over, which are extra dimensions as described by Kaluza and Klein. The extra five dimensions are arranged as a sphere. The four dimensions of Polyakov are curved, too, but in the opposite way from a sphere; such spaces are sometimes called saddle-shaped. These correspond to universes with dark energy, but where the dark energy is negative.””
