Paper 4, Section I, B

Further Complex Methods | Part II, 2014

Let f:CCf: \mathbb{C} \rightarrow \mathbb{C} be a function such that

f(z+ω1)=f(z),f(z+ω2)=f(z)f\left(z+\omega_{1}\right)=f(z), \quad f\left(z+\omega_{2}\right)=f(z)

where ω1,ω2C\{0}\omega_{1}, \omega_{2} \in \mathbb{C} \backslash\{0\} and ω1/ω2\omega_{1} / \omega_{2} is not real. Show that if ff is analytic on C\mathbb{C} then it is a constant. [Liouville's theorem may be used if stated.] Give an example of a non-constant meromorphic function which satisfies (1).

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