Borcea's Toeplitz reformulation of the 2-variance conjecture

From papers

Assume n3n\geq3, choose a1,,an1Ca_1,\dots,a_{n-1}\in\mathbb C, and set

a0=k=1n1ak.a_0=-\sum_{k=1}^{n-1}a_k.

Let BB be the (n1)×(n1)(n-1)\times(n-1) Toeplitz matrix

B=(a0a1an2\an1a0a1\a2an1a0).B=\begin{pmatrix}a_0&a_1&\dots&a_{n-2}\a_{n-1}&a_0&a_1&\dots\vdots&\ddots&\ddots&\vdots\a_2&\dots&a_{n-1}&a_0\end{pmatrix}.

Borcea's Toeplitz conjecture. The matrix BB has at least one eigenvalue λ\lambda satisfying

λ2k=1n1ak2.|\lambda|^2\leq\sum_{k=1}^{n-1}|a_k|^2.

The source states that this matrix conjecture is equivalent to Statement (i), and hence to the 2-variance conjecture. No resolution is given.

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Sources & referencesView supporting material

Primary source

Dmitry Khavinson, Rajesh Pereira, Mihai Putinar, Edward B. Saff and Serguei Shimorin, “Borcea's variance conjectures on the critical points of polynomials”, arXiv:1010.5167 (2011).

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