Matrix Gross–Witten sum-rule conjecture

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Let Σ∈Mp,1(T)\Sigma\in\mathcal M_{p,1}(\mathbb T) have infinite support, and let (αk)k≥0∈(Bp)N0(\boldsymbol\alpha_k)_{k\geq0}\in(\mathbb B_p)^{\mathbb N_0} be its matrix Verblunsky coefficients. Let T(α0,… )T(\boldsymbol\alpha_0,\dots) be the matrix expression specified in the source, and let Hp(g)H_p({\tt g}) be a constant. Matrix Gross–Witten sum-rule conjecture. If ∣g∣≤1|{\tt g}|\leq1, then

K(1⋅GW⁡−g∣Σ)=∑k=0∞−log⁡det⁡(1−αkαk†)+g ℜ tr⁡T(α0,… )+Hp(g).\mathcal K(\mathbf 1\cdot\operatorname{GW}_{-{\tt g}}\mid\Sigma)=\sum_{k=0}^{\infty}-\log\det(\mathbf 1-\boldsymbol\alpha_k\boldsymbol\alpha_k^\dagger)+{\tt g}\,\Re\,\operatorname{tr}T(\boldsymbol\alpha_0,\dots)+H_p({\tt g}).

If ∣g∣>1|{\tt g}|>1, a similar identity holds with the additional term ∑i=1N−F−g+(λi−)+∑n=1N+F−g−(λi+)\sum_{i=1}^{N^-}\mathcal F^+_{-{\tt g}}(\lambda_i^-)+\sum_{n=1}^{N^+}\mathcal F^-_{-{\tt g}}(\lambda_i^+) on the left-hand side. This is presented as the matrix analogue of the scalar Gross–Witten sum rules, but the supplied text gives no resolution status.

References

Primary source

Fabrice Gamboa, Jan Nagel and Alain Rouault, “Sum rules and large deviations for spectral measures on the unit circle”, arXiv:1604.06934 (2017).

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