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Part CCSIR NET December 2023hurwitz-zeros-escape

Hurwitz zeros escape

For every n ≥ 1, consider the entire function pn(z)=∑k=0np_{n}(z) = \sum_{k=0}^{n} zᵏ/k!. Which of the following statements are true?

  1. A.The sequence (pn)(p_{n}) converges to an entire function uniformly on compact subsets of C\mathbb{C}.✓ Correct
  2. B.For all n≥1,pnn \ge 1, p_{n} has a zero in the set {z∈Cz \in \mathbb{C} : |z| ≤ 2023}.
  3. C.There exists a sequence (zn)(z_{n}) of complex numbers such that lim |znz_{n}| =∞= \infty and pn(zn)=0p_{n}(z_{n}) = 0 for all n ≥ 1.✓ Correct
  4. D.Let SnS_{n} be the set of all zeros of pnp_{n}. If an=a_{n} = minz∈Snmin_{z\in{}S_{n}} |z|, then an→∞a_{n} \to \infty as n→∞n \to \infty.✓ Correct

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, and why this one tests standard counterexample.

See pricing

50 are analysed free — try those first.

The trap it tests

Standard counterexample

There is a canonical object that settles this. Recognising it is the whole question.

Drill statements like this

Related counterexample: Zeros of a non-constant holomorphic function cannot accumulate

More on this topic

The chapter behind this: Analyticity, the identity theorem and zeros — free to read

From Analytic Functions › Power series and analyticity

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