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Part BCSIR NET December 2024harmonic-modulus-squared-forces-constant

Harmonic modulus squared forces constant

Let 𝔻 = {z = x + iy : |z| < 1} be the open unit disc and f : 𝔻 holomorphic function such that f(0) = 0. Let |f(z)|, and . Which of the following statements is FALSE?

  1. A.f can be extended to as an entire function.
  2. B.f must have infinitely many zeros in 𝔻.
  3. C.f is not a polynomial.
  4. D.exp(f) cannot take every complex value.

You have the answer. Trap Analysis is why the other three were written.

Not a worked solution repeated four times — the specific reasoning error each wrong option was built to reward.

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50 are analysed free — try those first.

Related counterexample: A harmonic function on any domain has a harmonic conjugate

More on this topic

The chapter behind this: Cauchy–Riemann — what they do and do not give you — free to read

From Analytic FunctionsCauchy–Riemann equations, harmonic functions

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