Unified field theory classical field theory and, two years later, that of Theodor Kaluza, who extended General Relativity to five dimensions. Continuing in this latter direction, Oscar Klein proposed in 1926 that the fourth spatial dimension be curled up into a small, unobserved circle. In Kaluza–Klein theory, the gravitational curvature of the extra spatial direction behaves as an additional force similar to electromagnetism. These and other models of electromagnetism and gravity were pursued by Albert Einstein in his attempts at a classical unified field theory. By 1930 Einstein had already considered the Einstein–Maxwell–Dirac System [Dongen]. This system is (heuristically) the super-classical [Varadarajan] limit
Unified neutral theory of biodiversity not straight, but the slope changes from being steep at small areas, shallower at intermediate areas, and steep at the largest areas. The formula for species composition may be used to calculate the expected number of species present in a community under the assumptions of the Unified Theory. In symbols where θ is the fundamental biodiversity number. This formula specifies the expected number of species sampled in a community of size "J". The last term, formula_63, is the expected number of "new" species encountered when adding one new individual to the community. This is an increasing function of θ and