Problems / number-theory
number-theory / Multiplicative number theory; Euler's totient function
Erdős's totient-fiber conjecture: φ(m)=n has more than n1−ε solutions for infinitely many n
Theorem 1.1: for every ε>0 there are infinitely many n with g(n)>n1−ε, which is optimal in the exponent because g(n)≪ηn1+η. The input is Theorem 1.2: for fixed 0<δ<1/4, at least x1−o(1) primes p∈(2x,5x] have P+(p−1)≤xδ; in particular there are infinitely many primes with P+(p−1)≤pε for every ε>0. It does not give a positive proportion of such primes (that stronger statement is in the Poisson-Dirichlet companion), and the o(1) is not made explicit.