Asymptotic spectral properties of the Hilbert $L$-matrix

Abstract

We study asymptotic spectral properties of the generalized Hilbert $L$-matrix $$L_{n}(\nu)=\left(\frac{1}{\max(i,j)+\nu}\right)_{i,j=0}^{n-1},$$ for large order $n$. First, for general $\nu\neq0,-1,-2,\dots$, we deduce the asymptotic distribution of eigenvalues of $L_{n}(\nu)$ outside the origin. Second, for $\nu>0$, asymptotic formulas for small eigenvalues of $L_{n}(\nu)$ are derived. Third, in the classical case $\nu=1$, we also prove asymptotic formulas for large eigenvalues of $L_{n}\equiv L_{n}(1)$. I particular, we obtain an asymptotic expansion of $\|L_{n}\|$ improving Wilf's formula for the best constant in truncated Hardy's inequality.Comment: 18 pages, dedicated to the memory of Harold Widom, accepted for publication in SIAM J. Matrix Anal. App