Locality principle

A collective concept that combines a number of assertions related mainly to elliptic (in some cases to hypo-elliptic) equations (operators) and that follows from the pointwise character of the singularity of a fundamental solution for this class of equations. For example, an elliptic operator with variable coefficients, written in the form

can be represented, in an appropriate sense, in a neighbourhood of a point as a sum

where the first term is an operator with constant coefficients, and is "sufficiently small" in the given neighbourhood.

References

[1]	N. Dunford, J.T. Schwartz, "Linear operators. Spectral theory" , 2 , Interscience (1963)