Argument principle and zero–pole counts
For meromorphic f, a positively oriented simple closed piecewise C¹ contour γ avoiding its zeros and poles gives (2πi)⁻¹∮γf′/f dz=N−P=Ind(f∘γ,0), counting interior zeros and poles with their multiplicities.
Key knowledge
For meromorphic f, a positively oriented simple closed piecewise C¹ contour γ avoiding its zeros and poles gives (2πi)⁻¹∮γf′/f dz=N−P=Ind(f∘γ,0), counting interior zeros and poles with their multiplicities.
Conditions and scope
- f is meromorphic on a neighborhood of the closed interior and has no zero or pole on γ.
- The image curve's winding number may exceed one even though γ is simple.
Sources · 1
References
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Evidence and review
Setup and Theorems 11.1/11.4, sections 11.2–11.2.2; local logarithmic derivative residues checked.
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