Let be a ringed space. Consider the subsheaf of sets of the structure sheaf such that for each open subset , consists of only the regular sections of over , i.e. those elements for which implies for all for all opens . Consider the presheaf of rings on
which assigns to the ring of fractions of with denominators in ; its sheafification is called the sheaf of (germs of) meromorphic functions on . The sections of over are called the meromorphic functions on X and we denote this ring .
For every open subset there is a canonical isomorphism between and the restriction of to .
For every point there is a canonical isomorphism between the stalk and .
Alexander Grothendieck, Jean Dieudonné, EGA (IV, 20.1).
Stacks Project, sheaf of meromorphic functions and sections, tag 01X1.
Steven L. Kleiman, Misconceptions about , L’Enseignement Mathématique 25 (1979), 203–206 (doi:10.5169/seals-50379)
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