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Morera's theorem (Theorem)

Morera's theorem provides the converse of Cauchy's integral theorem.

Theorem [1] Suppose $ G$ is a region in $ \mathbb{C}$, and $ f:G\to \mathbb{C}$ is a continuous function. If for every closed triangle $ \Delta$ in $ G$, we have

$\displaystyle \int_{\partial \Delta} f\, dz = 0,$
then $ f$ is analytic on $ G$. (Here, $ \partial \Delta$ is the piecewise linear boundary of $ \Delta$.)

In particular, if for every rectifiable closed curve $ \Gamma$ in $ G$, we have $ \int_{\Gamma} f\, dz = 0,$ then $ f$ is analytic on $ G$. Proofs of this can be found most undergraduate books on complex analysis [2,3].

Bibliography

1
W. Rudin, Real and complex analysis, 3rd ed., McGraw-Hill Inc., 1987.
2
E. Kreyszig, Advanced Engineering Mathematics, John Wiley & Sons, 1993, 7th ed.
3
R.A. Silverman, Introductory Complex Analysis, Dover Publications, 1972.



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Cross-references: complex analysis, proofs, closed curve, rectifiable, piecewise, analytic, triangle, closed, continuous function, region, Cauchy's integral theorem, converse
There are 2 references to this entry.

This is version 9 of Morera's theorem, born on 2002-08-23, modified 2005-05-16.
Object id is 3339, canonical name is MorerasTheorem.
Accessed 4167 times total.

Classification:
AMS MSC30D20 (Functions of a complex variable :: Entire and meromorphic functions, and related topics :: Entire functions, general theory)

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