Finite Differences of the Logarithm of the Partition Function

William Y.C. Chen, Larry X.W. Wang and Gary Y.B. Xie

  Abstract:  Let p(n) denote the partition function. DeSalvo and Pak proved that for n ≥ 2, as conjectured by Chen. Moreover, they conjectured that a sharper inequality holds for n ≥ 45. In this paper, we prove the conjecture of Desalvo and Pak by giving an upper bound for 2log p(n - 1), where Δ is the difference operator with respect to n. We also show that for given r ≥ 1 and sufficiently large n, (-1)Δrlog p(n) > 0. This is analogous to the positivity of finite differences of the partition function. It was conjectured by Good and proved by Gupta that for given r ≥ 1, Δrp(n) > 0 for sufficiently large n.

  AMS Classification:  05A20, 11B68

  Keywords:  partition function, log-concavity, finite difference, the Lambert W function, the Hardy-Ramanujan-Rademacher formula

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