3.1 General Theories
- Grand Unification, grand unified theory, or GUT is one of several very similar unified field theories or models in physics that predicts that at extremely high energies (above 1014 GeV), the electromagnetic, weak nuclear, and strong nuclear forces are fused into a single unified field. Thus far, physicists have been able to merge electromagnetism and the weak nuclear force into the electroweak force, and work is being done to merge electroweak and quantum chromodynamics into a QCD-electroweak interaction sometimes called the electrostrong force.

- Theory of everything (TOE) is still a hypothetical theory of theoretical physics that fully explains and links together all known physical phenomena. In quantum physics the term describes a theory that would unify or explain through a single model the theories of all fundamental interactions of nature. There have been many theories of everything proposed by theoretical physicists over the last century, but none has been confirmed experimentally because the theories of quantum mechanics and general relativity are hard to combine. Many physicists -but not all- believe that 11-dimensional M-theory, described in many sectors by matrix string theory and in many other sectors by perturbative string theory is the complete theory of everything.