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Bosonic string theory is the original version of string theory, developed in the late 1960s.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 string theory) became the real focus.
In bosonic string theory, spacetime is 26-dimensional, while in superstring theory it is 10-dimensional, and in M-theory it is 11-dimensional. In order to describe real physical phenomena using string theory, one must therefore imagine scenarios in which these extra dimensions would not be observed in experiments.
Schwarz and Scherk argued that string theory had failed to catch on because physicists had underestimated its scope. This led to the development of bosonic string theory. String theory is formulated in terms of the Polyakov action, [37] which describes how strings move through space and time. Like springs, the strings tend to contract to ...
For example, the bosonic string in 26 dimensions has a worldsheet conformal field theory consisting of 26 free scalar bosons. Meanwhile, a superstring worldsheet theory in 10 dimensions consists of 10 free scalar fields and their fermionic superpartners .
Because string theory implies that the Universe has more dimensions than we expect—26 for bosonic string theories and 10 for superstring theories—we have to find a reason why the extra dimensions are not apparent. One possibility would be that the visible Universe is in fact a very large D-brane extending over three spatial dimensions.
The Nambu–Goto action is the simplest invariant action in bosonic string theory, and is also used in other theories that investigate string-like objects (for example, cosmic strings). It is the starting point of the analysis of zero-thickness (infinitely thin) string behaviour, using the principles of Lagrangian mechanics.
This approach can be dated back to a paper by Gabriele Veneziano [1] that shows how an inflationary cosmological model can be obtained from string theory, thus opening the door to a description of pre-Big Bang scenarios. The idea is related to a property of the bosonic string in a curve background, better known as nonlinear sigma model.
Non-compact free bosonic CFTs with are used for describing non-critical string theory. In this context, a non-compact free bosonic CFT is called a linear dilaton theory . A free bosonic CFT with Q = 0 {\displaystyle Q=0} i.e. c = 1 {\displaystyle c=1} is a sigma model with a one-dimensional target space.