Peter R. W. McNamara ; Bruce E. Sagan
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Infinite log-concavity: developments and conjectures
dmtcs:2678 -
Discrete Mathematics & Theoretical Computer Science,
January 1, 2009,
DMTCS Proceedings vol. AK, 21st International Conference on Formal Power Series and Algebraic Combinatorics (FPSAC 2009)
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https://doi.org/10.46298/dmtcs.2678
Infinite log-concavity: developments and conjectures
Authors: Peter R. W. McNamara ; Bruce E. Sagan 1
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Peter R. W. McNamara;Bruce E. Sagan
1 Department of Mathematics [Lansing]
Given a sequence $(a_k)=a_0,a_1,a_2,\ldots$ of real numbers, define a new sequence $\mathcal{L}(a_k)=(b_k)$ where $b_k=a_k^2-a_{k-1}a_{k+1}$. So $(a_k)$ is log-concave if and only if $(b_k)$ is a nonnegative sequence. Call $(a_k)$ $\textit{infinitely log-concave}$ if $\mathcal{L}^i(a_k)$ is nonnegative for all $i \geq 1$. Boros and Moll conjectured that the rows of Pascal's triangle are infinitely log-concave. Using a computer and a stronger version of log-concavity, we prove their conjecture for the $n$th row for all $n \leq 1450$. We can also use our methods to give a simple proof of a recent result of Uminsky and Yeats about regions of infinite log-concavity. We investigate related questions about the columns of Pascal's triangle, $q$-analogues, symmetric functions, real-rooted polynomials, and Toeplitz matrices. In addition, we offer several conjectures.
Log-concave and unimodal sequences in algebra, combinatorics, and geometry: an update
2 Documents citing this article
Source : OpenCitations
Medina, Luis A.; Straub, Armin, 2015, On Multiple And Infinite Log-Concavity, Annals Of Combinatorics, 20, 1, pp. 125-138, 10.1007/s00026-015-0292-7.
Moll, Victor H.; Manna, Dante V., 2009, A Remarkable Sequence Of Integers, Expositiones Mathematicae, 27, 4, pp. 289-312, 10.1016/j.exmath.2009.02.005.