Crouzeix's conjecture for scaled q-numerical ranges

Let AA be an n×nn\times n matrix, let 0<q10<|q|\leq 1, and let Ωq\Omega_q denote the scaled qq-numerical range introduced in the source. For a polynomial pp with complex coefficients, the scaled qq-numerical-range conjecture.

p(A)max ⁣(1,2q1+1q2)supzΩqp(z).\|p(A)\|\leq\max\!\left(1,\frac{2|q|}{1+\sqrt{1-|q|^2}}\right)\sup_{z\in\Omega_q}|p(z)|.

This conjecture generalises Crouzeix's conjecture from the classical numerical range to scaled qq-numerical ranges. When q=1q=1, the set Ωq\Omega_q reduces to the numerical range W(A)W(A), recovering the known 1+21+\sqrt{2} spectral-constant bound; the proposed inequality is presented without a resolution in the source.

Sources & referencesView supporting material

Primary source

Ryan O'Loughlin and Jyoti Rani, “q-Numerical Ranges and Spectral Sets”, arXiv:2603.15536 (2026).

Progress summary

Never refreshed

Nothing recorded yet. Refresh searches the literature and the public web for attempts on this problem, and writes the first summary here.

Solutions 0

No solutions have been posted yet.