Construct an entire function f in complex with simple zeros at an = n^(1/2) for n belongs to natural numbers and no other zeros
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Expert's answer
2020-03-30T12:51:03-0400
By the Weierstrass factorizaion theorem we obtain that f(z)=n=1∏∞En(anz) is a entire function, such that {z:f(z)=0}={an}n∈N, and these zeros are simple, where En(z)=(1−z)exp(k=1∑nkzk)
Indeed
1) n→∞lim∣an∣=+∞
2)For every r>0 there is N such that ∣∣anr∣∣<21 for all n>N, thenn=1∑∞∣∣anr∣∣n+1=n=1∑N∣∣anr∣∣n+1+n=N+1∑∞∣∣anr∣∣n+1≤
≤n=1∑N∣∣anr∣∣n+1+n=N+1∑∞(21)n+1, so n=1∑∞∣∣anr∣∣pn+1 , where pn=n, is convergent series.
Then f(z)=n=1∏∞Epn(anz)=n=1∏∞En(anz) is a entire function with simple zeros {an}n∈N.
Answer: f(z)=n=1∏∞En(anz)=n=1∏∞En(nz), where En(z)=(1−z)exp(k=1∑nkzk)
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