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Lower bounds and complex-eigenvalue distribution under strong convergence

Establish a lower bound on the spectral radius and prove convergence of the empirical complex eigenvalue distribution for non-self-adjoint noncommutative polynomials P(X^N,(X^N)*) under strong convergence hypotheses; equivalently, show that complex eigenvalue behavior is controlled in the same limit as operator norms for such polynomials.

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Background

While strong convergence directly yields upper bounds on spectral radii for non-normal polynomials, lower bounds and distributional limits of complex eigenvalues remain poorly understood.

Progress in special cases (e.g., quadratic polynomials of Ginibre matrices) suggests the possibility of general results, but a broad theory aligning complex eigenvalue asymptotics with strong convergence is not yet available.

References

While an upper bound on the spectral radius follows directly from strong convergence by Lemma 4.7, a lower bound on the spectral radius and convergence of the empirical distribution of the complex eigenvalues remain largely open.

The strong convergence phenomenon (2507.00346 - Handel, 1 Jul 2025) in Section 6.9 (Complex eigenvalues)