On the log-concavity of $n$-th root of a sequence

Abstract: In recent years, the log-concavity of ${\sqrt[n]{S_n}}{n\geq 1}$ have been received a lot of attention. Very recently, Sun posed the following conjecture in his new book: the sequences ${\sqrt[n]{a_n}}{n\geq 2}$ and ${ \sqrt[n]{b_n}}{n\geq 1}$ are log-concave, where [ a_n:= \frac{1}{n}\sum{k=0}^{n-1} \frac{{n-1\choose k}^2{n+k\choose k}^2 }{4k^2-1} ] and [ b_n:= \frac{1}{n^3}\sum_{k=0}^{n-1} (3k^2+3k+1){n-1\choose k}^2 {n+k\choose k}^2. ] In this paper, two methods, semi-automatic and analytic methods, are used to confirm Sun's conjecture. The semi-automatic method relies on a criterion on the log-concavity of ${\sqrt[n]{S_n}}_{n\geq 1}$ given by us and a mathematica package due to Hou and Zhang, while the analytic method relies on a result due to Xia.