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Steinberg symbols modulo the trace class, holonomy, and limit theorems for Toeplitz determinants
Authors:Richard W. Carey   Joel D. Pincus
Affiliation:Department of Mathematics, University of Kentucky, Lexington, Kentucky 40511 ; 806 Hunt Lane, Manhasset, New York 11030
Abstract:Suppose that $phi=psi z^gamma$ where $gammain Z_+$ and $psi in text{rm Lip}_beta,,{1over 2}<beta<1$, and the Toeplitz operator $T_psi$ is invertible. Let $D_n(T_phi)$ be the determinant of the Toeplitz matrix $((hatphi _{i,j}))=((hatphi _{i-j})),quad 0leq i,jleq n ,$ where $hat phi_k={1over 2pi}int_0^{2pi} phi(theta)e^{-iktheta}, dtheta $. Let $P_n$ be the orthogonal projection onto $ker {S^*}^{n+1}=bigvee{1,e^{itheta}, e^{2itheta},ldots, e^{intheta}},$where $S=T_z$; set $Q_n=1-P_n$, let $H_omega$ denote the Hankel operator associated to $omega$, and set $tildeomega(t)=omega({1over t})$ for $tin mathbb{T} $. For the Wiener-Hopf factorization $psi=fbar g$ where $f, g$ and ${1over f },{1over g}in text{rm Lip}_betacap H^infty(mathbb{T} ), {1over 2}<beta<1$, put $E(psi)=expsum_{k=1}^infty k(log f)_k(log bar g)_{-k}$, $G(psi)=exp(logpsi)_0.$ Theorem A.     $D_n(T_phi)=(-1)^{(n+1)gamma} G(psi)^{n+1}E(psi) G({bar gover f})^gamma$

$cdot detbigg((T_{{fover bar g}z^{n+1}}cdot [1-H_{bar gover f} Q_{n-gam... ...^{alpha-1},z^{tau-1})bigg)_{gamma times gamma} cdot [1+O(n^{1-2beta})].$

Let $H^2(mathbb{T} )= {mathcal X}dotplus {mathcal Y}$ be a decomposition into $T_phi T_{phi^{-1}}$invariant subspaces, ${mathcal X}= bigcap_{n=1}^inftyoperatorname{ran} (T_phi T_{phi^{-1}})^n$and ${mathcal Y}=bigcup _{n=1}^inftyker (T_phi T_{phi^{-1}})^n$, so that $T_phi T_{phi^{-1}}$ restricted to ${mathcal X}$ is invertible, ${mathcal Y}$ is finite dimensional, and $T_phi T_{phi^{-1}}$ restricted to ${mathcal Y}$ is nilpotent. Let ${w_alpha}_1^gamma$ be the basis ${T_f z^alpha}_0^{gamma-1}$ for the null space of $T_phi T_{phi^{-1}}$, and let $u_alpha$ be the top vector in a Jordan root vector chain of length $m_alpha+1$ lying over $(-1)^{m_alpha}w_alpha$, i.e., $(T_phi T_{phi^{-1}})^{m_alpha}u_alpha =(-1)^{m_alpha}w_alpha$where $m_alpha=max{min Z_+:exists x,text{rm so that} (T_phi T_{phi^{-1}})^mx=w_alpha}^{-1}$. Theorem B.     $E( psi) G({bar gover f})^gamma=$ $ {prod_{lambdainsigma(T_{phi} T_{phi^{-1}})setminus {0}},lambda}over det( u_alpha,T_{1over g}z^{tau-1}) $ $ =left (bar gcup ftimes {bar gover f}cup z^gammaright )(mathbb{T} )$, the holonomy of a Deligne bundle with connection defined by the factorization $phi= fbar gz^gamma$. Note that the generalizations of the Szegö limit theorem for $D_n(T_phi)$which have appeared in the literature with $1$ instead of $ [1-H_{bar gover f} Q_{n-gamma} H_{({fover bar g})^{tilde{}}}]^{-1}$ have the defect that the limit of ${D_n(T_phi)over (-1)^{(n+1)gamma} G(psi)^{n+1} det(T_{{fover bar g}z^{n+1}}z^{alpha-1},z^{tau-1})}$ does not exist in general. An example is given with $ D_n(T_phi)neq 0$yet $ D_{gamma-1}(T_{{fover bar g}z^{n+1}})=0$ for infinitely many $n$.

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