Matrix Gross–Witten sum-rule conjecture

Let ΣMp,1(T)\Sigma\in\mathcal M_{p,1}(\mathbb T) have infinite support, and let (αk)k0(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 g1|{\tt g}|\leq1, then

K(1GWgΣ)=k=0logdet(1αkαk)+gtrT(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=1NFg+(λi)+n=1N+Fg(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.

Sources & referencesView supporting material

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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