Monday, 27 June 2011

nt.number theory - Reference for the expected number of prime factors of n larger than n^alpha is -log alpha

Do you mean that log(1/alpha) is the expected number of prime factors in (xalpha,x] when alphato0? For fixed alphain(0,1) what you are claiming is not true. For example,



|nlex:existsp|n;rmwith;sqrtxltplex|simxlog2



and



|nlex:plesqrtx;rmforall;p|n|sim(1log2)x.



When alphato0 it is not hard to prove what you need, but I am not sure where you can find a precise reference. For example, setting omega(n;y,z)=|p|n:yltplez| and following the proof of Theorem 6 in page 311 in Tenenbaum's book "Introduction to Analytic and Probabilistic Number Theory" gives that



|nlex:|omega(n;xalpha,x)log(1/alpha)|ge(1+delta)log(1/alpha)|llxalphaQ(1+delta),



where Q(1+delta)=int1+delta1logtdt.

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