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In this paper, we introduce the concept of an $m$-order $n$-dimensional generalized Hilbert tensor $mathcal{H}_{n}=(mathcal{H}_{i_{1}i_{2}cdots i_{m}})$, $$ mathcal{H}_{i_{1}i_{2}cdots i_{m}}=frac{1}{i_{1}+i_{2}+cdots i_{m}-m+a}, ain mathbb{R}setminusmathbb{Z}^-; i_{1},i_{2},cdots,i_{m}=1,2,cdots,n, $$ and show that its $H$-spectral radius and its $Z$-spectral radius are smaller than or equal to $M(a)n^{m-1}$ and $M(a)n^{frac{m}{2}}$, respectively, here $M(a)$ is a constant only dependent on $a$. Moreover, both infinite and finite dimensional generalized Hilbert tensors are positive definite for $ageq1$. For an $m$-order infinite dimensional generalized Hilbert tensor $mathcal{H}_{infty}$ with $a>0$, we prove that $mathcal{H}_{infty}$ defines a bounded and positively $(m-1)$-homogeneous operator from $l^{1}$ into $l^{p} (1<p<infty)$. The upper bounds of norm of corresponding positively homogeneous operators are obtained.
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In this paper, the $m-$order infinite dimensional Hilbert tensor (hypermatrix) is intrduced to define an $(m-1)$-homogeneous operator on the spaces of analytic functions, which is called Hilbert tensor operator. The boundedness of Hilbert tensor operator is presented on Bergman spaces $A^p$ ($p>2(m-1)$). On the base of the boundedness, two positively homogeneous operators are introduced to the spaces of analytic functions, and hence the upper bounds of norm of such two operators are found on Bergman spaces $A^p$ ($p>2(m-1)$). In particular, the norms of such two operators on Bergman spaces $A^{4(m-1)}$ are smaller than or equal to $pi$ and $pi^frac1{m-1}$, respectively.
The concepts of P- and P$_0$-matrices are generalized to P- and P$_0$-tensors of even and odd orders via homogeneous formulae. Analog to the matrix case, our P-tensor definition encompasses many important classes of tensors such as the positive definite tensors, the nonsingular M-tensors, the nonsingular H-tensors with positive diagonal entries, the strictly diagonally dominant tensors with positive diagonal entries, etc. As even-order symmetric PSD tensors are exactly even-order symmetric P$_0$-tensors, our definition of P$_0$-tensors, to some extent, can be regarded as an extension of PSD tensors for the odd-order case. Along with the basic properties of P- and P$_0$-tensors, the relationship among P$_0$-tensors and other extensions of PSD tensors are then discussed for comparison. Many structured tensors are also shown to be P- and P$_0$-tensors. As a theoretical application, the P-tensor complementarity problem is discussed and shown to possess a nonempty and compact solution set.
In this paper, we introduce the concept of Z$_1$-eigenvalue to infinite dimensional generalized Hilbert tensors (hypermatrix) $mathcal{H}_lambda^{infty}=(mathcal{H}_{i_{1}i_{2}cdots i_{m}})$, $$ mathcal{H}_{i_{1}i_{2}cdots i_{m}}=frac{1}{i_{1}+i_{2}+cdots i_{m}+lambda}, lambdain mathbb{R}setminusmathbb{Z}^-; i_{1},i_{2},cdots,i_{m}=0,1,2,cdots,n,cdots, $$ and proved that its $Z_1$-spectral radius is not larger than $pi$ for $lambda>frac{1}{2}$, and is at most $frac{pi}{sin{lambdapi}}$ for $frac{1}{2}geq lambda>0$. Besides, the upper bound of $Z_1$-spectral radius of an $m$th-order $n$-dimensional generalized Hilbert tensor $mathcal{H}_lambda^n$ is obtained also, and such a bound only depends on $n$ and $lambda$.
We reformulate entanglement wedge reconstruction in the language of operator-algebra quantum error correction with infinite-dimensional physical and code Hilbert spaces. Von Neumann algebras are used to characterize observables in a boundary subregion and its entanglement wedge. Assuming that the infinite-dimensional von Neumann algebras associated with an entanglement wedge and its complement may both be reconstructed in their corresponding boundary subregions, we prove that the relative entropies measured with respect to the bulk and boundary observables are equal. We also prove the converse: when the relative entropies measured in an entanglement wedge and its complement equal the relative entropies measured in their respective boundary subregions, entanglement wedge reconstruction is possible. Along the way, we show that the bulk and boundary modular operators act on the code subspace in the same way. For holographic theories with a well-defined entanglement wedge, this result provides a well-defined notion of holographic relative entropy.
The thermal equilibrium distribution over quantum-mechanical wave functions is a so-called Gaussian adjusted projected (GAP) measure, $GAP(rho_beta)$, for a thermal density operator $rho_beta$ at inverse temperature $beta$. More generally, $GAP(rho)$ is a probability measure on the unit sphere in Hilbert space for any density operator $rho$ (i.e., a positive operator with trace 1). In this note, we collect the mathematical details concerning the rigorous definition of $GAP(rho)$ in infinite-dimensional separable Hilbert spaces. Its existence and uniqueness follows from Prohorovs theorem on the existence and uniqueness of Gaussian measures in Hilbert spaces with given mean and covariance. We also give an alternative existence proof. Finally, we give a proof that $GAP(rho)$ depends continuously on $rho$ in the sense that convergence of $rho$ in the trace norm implies weak convergence of $GAP(rho)$.
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