nLab theory of everything

Idea

In quantum physics, specifically in fundamental physics/high energy physics, the term “theory of everything” is used to refer to a (hypothetical) theory which coherently subsumes “all” of fundamental physics, in some sense.

Taken at face value this terminology has its evident problems, but its usage is to be understood in the context of the situation of the field of theoretical physics at the turn to the 21st century, where it has the evident and justified restricted meaning of a theory which, somehow, coherently subsumes and possibly explains from more fundamental principles both:

• the standard model of particle physics, based on Yang-Mills theory;

• the standard model of cosmology, based on Einstein gravity.

One issue here is to unify these at the level of quantum field theory proper (which seems to be accomplished by string theory at least in broad outline, for more see at quantum gravity), the next issue is to go beyond perturbative quantum field theory and account for still largely elusive non-perturbative effects (working title: “M-theory”) such as confinement via the mass gap of QCD. Yet another issue is to possibly find an explanation for some of the random-looking structures in these standard models, for more on this see also at grand unified field theory and exceptional naturalism; or else to understand these as just random artefacts (in a “multiverse” of physically allowed structures).

Notice here that in their colloquial meaning the terms theory of everything and grand unified field theory largely overlap, but that as technical terms they are understood quite differently: The term grand unified field theory is used almost exclusively for gauge group-unification, which is not even part of all proposals for a “theory of everything”.

Related concepts

• high energy physics

• quantum gravity

• grand unified theory

• mass gap problem

• mathematical physics

• string theory, M-theory

• exceptional naturalism

• gauge coupling unification

• multiverse

References

Back in the day, David Hilbert would speak of Weltgesetze (“world laws”), see starting on page 396 (esp. 417, 423) in:

• Tilman Sauer, Ulrich Majer with Arne Schirrmacher, Heinz-Jürgen Schmidt (eds.): David Hilbert’s Lectures on the foundations of physics 1915-1927 — Relativity, Quantum Theory and Epistemology, Springer (2009) [doi:10.1007/b12915]

See also:

• Wikipedia, Theory of everything