Unified field theory

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Uniform field theories are field theories that pursue the goal of summarizing all matter and force fields of the universe in one formula, the “unified” or “uniform field”. A unified field theory , sometimes called a world formula , should explain the properties of all interactions as well as the properties ( spin , mass , charge ) of all elementary particles .

history

Historically, the work of James Clerk Maxwell reached a first level of standardization - the four Maxwell's equations could explain electrical and magnetic phenomena in a uniform manner and, above all, showed the close connection between electricity and magnetism . The symmetries hidden in the equations led to the Lorentz transformation and thus later to the discovery of the special theory of relativity by Albert Einstein .

Einstein then formulated a relativistically correct theory of gravitation , the general theory of relativity . From the 1920s on, he spent the rest of his life looking for a unification of electromagnetism and gravity . Among other things, in April 1929 he submitted a work to the Prussian Academy of Sciences entitled Unified Field Theory and Hamiltonian Principle . One approach that Einstein pursued was the so-called Kaluza-Klein theory , which tries to find a unified field theory in spaces with more than four dimensions. The Kaluza-Klein theory is considered to be the forerunner of the string theory that has been popular since the end of the 20th century . At the same time, Einstein's experiments marked the preliminary end of the effort to develop a “classical” unified field theory.

With the discovery of quantum mechanics and two other interactions - strong and weak nuclear power - in the 1930s, the goal of a unified theory became a long way off. The connection of relativity theory and quantum mechanics led to quantum field theory .

In the 1950s and 1960s , Heisenberg and his students tried to derive a nonlinear field theory based on the Dirac equation . This was to explain and order the large number of newly discovered elementary particles. However, this approach turned out to be a dead end. With the quarks, Gell-Mann finally brought order to the “particle zoo” in a completely different way, namely with a quantum field theory.

Today's approaches

Today quantum field theories for three of the four interactions are well known. Only for the oldest known interaction, gravitation, there is no quantum theory. The quantum electrodynamics and quantum flavor dynamics (theory of weak interactions of quarks) were in the 1970s by Steven Weinberg , Sheldon Lee Glashow and Abdus Salam for electroweak theory unified. However, attempts to unify the electroweak theory with quantum chromodynamics failed (see, for example, proton decay ).

A promising approach for a unified field theory is the superstring theory, in which great progress was made in the 1990s under the name M-theory . Here it seems possible to actually unify all four interactions, but the theory is still at an early stage of development. Another approach to the formulation of a quantum theory of gravity is the so-called loop quantum gravity .

There are also other, mostly controversial or little-noticed approaches. For example, in 2007 Antony Garrett Lisi published an approach entitled “An Exceptionally Simple Theory of Everything” in the arXiv . This approach is called the E8 theory because of the mathematics behind it .

literature

  • Tian Y.Cao: Conceptual developments of 20th century field theories. Cambridge Univ. Press, Cambridge 1998, ISBN 0-521-63420-2
  • Vladimir P. Vizgin: Unified field theories in the first third of the 20th century. Birkhäuser, Basel 1994, ISBN 0-8176-2679-4
  • Ernst Schmutzer: Projective unified field theory - with applications in cosmology and astrophysics . German, Frankfurt 2004, ISBN 3-8171-1726-4
  • H.Galić: Phenomenology of unified theories - from standard model to supersymmetry. World Scientific, Singapore 1984, ISBN 9971-966-12-3
  • Marie A. Tonnelat: Einstein's unified field theory. Gordon and Breach, New York 1966
  • Václav Hlavatý: Geometry of Einstein's unified field theory. Noordhoff, Groningen 1957
  • Larry Silverberg: Unified field theory - for the engineer and the applied scientist. Wiley-VCH-Verl., Weinheim 2009, ISBN 978-3-527-40788-0

Individual evidence

  1. ↑ Einstein's new field work . In: Vossische Zeitung , April 4, 1929, p. 11-
  2. ^ AG Lisi (2007). "An Exceptionally Simple Theory of Everything"