Classical unified field theories Classical unified field theories Since the 19th century, some physicists, notably Albert Einstein, have attempted to develop a single theoretical framework that can account for all the fundamental forces of nature – a unified field theory. Classical unified field theories are attempts to create a unified field theory based on classical physics. In particular, unification of gravitation and electromagnetism was actively pursued by several physicists and mathematicians in the years between the two World Wars. This work spurred the purely mathematical development of differential geometry. This article describes various attempts at formulating a classical (non-quantum), relativistic unified field theory. For
Grand Unified Theory Lie group which contains the standard model, and upon which the first Grand Unified Theory was based, is Such group symmetries allow the reinterpretation of several known particles as different states of a single particle field. However, it is not obvious that the simplest possible choices for the extended "Grand Unified" symmetry should yield the correct inventory of elementary particles. The fact that all currently known matter particles fit nicely into three copies of the smallest group representations of and immediately carry the correct observed charges, is one of the first and most important reasons why people believe that a