superstring theory

Definition: A unified theory of the fundamental interactions involving supersymmetry, in which the basic objects are one-dimensional superstrings. Superstrings are thought to have a length scale of about 10^-35m and, since very short distances are associated with very high energies, they should have energy scales of about 10¹⁹ GeV, which is far beyond the energy of any accelerator that can be envisaged. Strings are only consistent as quantum theories in 10 (or more)-dimensional space-time. It is thought that four macroscopic dimensions arise according to Kaluza-Klein theory, with the remaining dimensions being 'curled up' to become very small. One of the most attractive features of the theory of superstrings is that it leads to spin 2 particles, which are identified as gravitons. Thus, a superstring theory automatically contains a quantum theory of the gravitational interaction. It is thought that superstrings are free of the infinities that cannot be removed by renormalisation, which plague attempts to construct a quantum field theory incorporating gravity. There is some evidence that superstring theory is free of infinities but not a complete proof yet. Although there is no direct evidence for superstrings, some features of superstrings are compatible with the experimental facts of elementary particles, such as the possibility of particles that do not respect parity, as found in weak interactions. Also Known As: string theory