Superstring

Superstring (supersymmetric string) is one of the main objects of string theory research. The versatility of the object does not allow him to give an unambiguous definition, however, as its name implies, the superstring contains supersymmetry.

Supersymmetry is the symmetry between bosons (carriers of interactions) and fermions (components of matter). And although there are still no clear indications of such symmetry in experiments, for the union of matter and "light" it is apparently a necessary element.

Bosons and fermions have different quantum statistics, Bose-Einstein and Fermi-Dirac, respectively, and therefore it is not so easy to combine them into one class, without violating any of the physical principles . So, the simplicity of introducing supersymmetry into quantum field theory and string theory is somewhat surprising.

As already mentioned in the articles on boson and fermion strings, the coordinates of a parameterized string in D-dimensional space can be viewed either as a set of two-dimensional scalar fields consisting of D pieces and then the D-vector and two-dimensional scalar supersymmetric partners will be the D-vector and two-dimensional real ( Presentation Majorana) spinor. Or, as part of the D-dimensional superspace, is bosonic, and then the Fermi remainder of the variables of superspace becomes the superpartner of the boson part. In the first case, we return again to the model of Ramon-Nevier-Schwartz (RNS 1971-1977), in the second we arrive at the Green-Schwartz model (GS 1981-1984). The superspace simply combines the boson and fermion coordinates, and although these coordinates have a different structure, there is a way to move from one coordinate to another. This is intuitively clear, since, in principle, 2 fermions can form a boson, then with the help of additional fermions, there is always the possibility to move from bosons to fermions and back.

The introduction of supersymmetry into string theory was possible in two ways: supersymmetry of the world surface and space-time supersymmetry. In a sense, they are one and the same, since the dynamics of space-time is closely related to conformal field theory. But the field correlations of these two approaches in studying the interaction of strings are still not clear (see Random Surfaces )

As expected, this unusual hybrid of boson and fermion strings inherits a smaller critical dimension in string theory, namely D = 10, however, both the RNS model, after the GSO projection, and the GS model do not contain vacuum instability - the tachyon.