Analytic Continuation - Formal Definition of A Germ

Formal Definition of A Germ

Let

be a power series converging in the disc Dr(z0) defined by

.

Note that without loss of generality, here and below, we will always assume that a maximal such r was chosen, even if that r is ∞. Also note that it would be equivalent to begin with an analytic function defined on some small open set. We say that the vector

g = (z0, α0, α1, α2, ...)

is a germ of f. The base g0 of g is z0, the stem of g is (α0, α1, α2, ...) and the top g1 of g is α0. The top of g is the value of f at z0, the bottom of g.

Any vector g = (z0, α0, α1, ...) is a germ if it represents a power series of an analytic function around z0 with some radius of convergence r > 0. Therefore, we can safely speak of the set of germs .

Read more about this topic:  Analytic Continuation

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