Classical unified field theories describe the properties of the electromagnetic field as a purely geometric phenomenon. Einstein tried to form a generalized theory of gravitation that would unify the gravitational and electromagnetic forces (and perhaps others), guided by a belief in a single origin for the entire set of physical laws. These attempts initially concentrated on additional geometric notions such as vierbeins and "distant parallelism", but eventually centered around treating both the metric tensor and the affine connection as fundamental fields. (Because they are not independent, the metric-affine theory was somewhat complicated.) In general relativity, these fields are symmetric (in the matrix sense), but
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