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After Calabi–Yau manifolds had entered physics as a way to compactify extra dimensions in string theory, many physicists began studying these manifolds. In the late 1980s, several physicists noticed that given such a compactification of string theory, it is not possible to reconstruct uniquely a corresponding Calabi–Yau manifold. [90]
Bosonic string theory is the original version of string theory, developed in the late 1960s and named after Satyendra Nath Bose. It is so called because it contains only bosons in the spectrum. In the 1980s, supersymmetry was discovered in the context of string theory, and a new version of string theory called superstring theory (supersymmetric ...
Some physicists (e.g., John Baez et al.) have speculated that the exceptional Lie groups E 6, E 7 and E 8 having maximum orthogonal subgroups SO(10), SO(12) and SO(16) may be related to theories in 10, 12 and 16 dimensions; 10 dimensions corresponding to string theory and the 12 and 16 dimensional theories being yet undiscovered but would be ...
At low energies, type IIB string theory is described by type IIB supergravity in ten dimensions which is a chiral theory (left–right asymmetric) with (2,0) d=10 supersymmetry; the fact that the anomalies in this theory cancel is therefore nontrivial.
Unlike supergravity theory, string theory was able to accommodate the chirality of the standard model, and it provided a theory of gravity consistent with quantum effects. [22] Another feature of string theory that many physicists were drawn to in the 1980s and 1990s was its high degree of uniqueness.
Itzhak Bars has proposed models of a two-time physics, noting in 2001 that "The 2T-physics approach in d + 2 dimensions offers a highly symmetric and unified version of the phenomena described by 1T-physics in d dimensions." [4] [5] F-theory, a branch of modern string theory, describes a 12-dimensional spacetime having two dimensions of time ...
However, for string theory to be mathematically consistent, the strings must live in a universe with ten dimensions. String theory explains our perception of the universe to have four dimensions (three space dimensions and one time dimension) by imagining that the extra six dimensions are "curled up", to be so small that they can't be observed ...
Furthermore, type IIA theory in strong coupling behaves like an 11-dimensional theory, with the dilaton field playing the role of an eleventh dimension. This 11-dimensional theory is known as M-theory. Unlike the T-duality, however, S-duality has not been proven to even a physics level of rigor for any of the aforementioned cases.