The Reverse Ultra Log-Concavity of the Boros-Moll Polynomials

Abstract

We prove the reverse ultra log-concavity of the Boros-Moll polynomials. We further establish an inequality which implies the log-concavity of the sequence $\{i!d_i(m)\}$ for any $m\ge 2$, where $d_i(m)$ are the coefficients of the Boros-Moll polynomials $P_m(a)$. This inequality also leads to the fact that in the asymptotic sense, the Boros-Moll sequences are just on the borderline between ultra log-concavity and reverse ultra log-concavity. We propose two conjectures on the log-concavity and reverse ultra log-concavity of the sequence $\{d_{i-1}(m)d_{i+1}(m)/d_i(m{)}^2\}$ for $m\ge 2$.

9 pages; Final version, to appear in Proc. Amer. Math. Soc