Matching Tag: operator-theory
Foci conjecture. If cl ( W ( T ) ) \operatorname{cl}(W(T)) cl ( W ( T )) is an elliptical disk, then its foci are contained in { 0 , 1 , − 1 } \{0,1,-1\} { 0 , 1 , − 1 } .
Let A α 2 A^2_\alpha A α 2 be the weighted Bergman space on D \mathbb{D} D , with α > − 1 \alpha>-1 α > − 1 , and let M ⊆ A α 2 M\subseteq A^2_\alpha M ⊆ A α 2 be invariant under the multiplication operator S f ( z ) = z f ( z ) S f(z)=z f(z) S f ( z ) = z f ( z ) . De…
For every separable Hilbert space E \mathcal E E , every B ∈ H 1 ∞ ( L ( E ) ) B\in H^\infty_1(L(\mathcal E)) B ∈ H 1 ∞ ( L ( E )) , and every α > − 1 \alpha>-1 α > − 1 , the associated sub-Bergman spaces satisfy…
Given a bounded vertex-weight family μ = ( μ v i , j ) ( i , j ) ∈ N × N \mu=(\mu_{v_{i,j}})_{(i,j)\in\mathbb{N}\times\mathbb{N}} μ = ( μ v i , j ) ( i , j ) ∈ N × N and the associated backward shift B μ B_{\mu} B μ on the sequence space of the infinite-qu…
For every integer n ≥ 1 n\ge 1 n ≥ 1 , every real number ρ > 1 \rho>1 ρ > 1 , and all complex numbers z 1 , … , z n z_1,\ldots,z_n z 1 , … , z n satisfying ∣ z j ∣ ≤ ρ |z_j|\le \rho ∣ z j ∣ ≤ ρ for 1 ≤ j ≤ n 1\le j\le n 1 ≤ j ≤ n , prove that…
Fix 0 < α , r < ∞ 0<\alpha,r<\infty 0 < α , r < ∞ . For every 0 < p , q ≤ ∞ 0<p,q\leq\infty 0 < p , q ≤ ∞ , determine whether, for every f ∈ C 1 ( [ − 1 , 1 ] ) f\in C^1([-1,1]) f ∈ C 1 ([ − 1 , 1 ]) satisfying f ( 0 ) = 0 f(0)=0 f ( 0 ) = 0 and ∣ f ′ ( t ) ∣ ≲ ∣ t ∣ α |f'(t)|\lesssim |t|^\alpha ∣ f ′ ( t ) ∣ ≲ ∣ t ∣ α , and every real sequence…
Fix α > 1 \alpha>1 α > 1 . Let G n ∼ G ( n , α / n ) G_n\sim G(n,\alpha/n) G n ∼ G ( n , α / n ) , let B n B_n B n be its non-backtracking matrix, and order the eigenvalues by nonincreasing modulus, so that…
Given Schur-class functions b 1 , b 2 b_1,b_2 b 1 , b 2 on the unit disk D \mathbb{D} D and an analytic self-map φ : D → D \varphi:\mathbb{D}\to\mathbb{D} φ : D → D , characterize when the composition operator…
Let A \mathcal A A be a uniform algebra, let H H H be a Hilbert space, let π : A → B ( H ) \pi:\mathcal A\to\mathcal B(H) π : A → B ( H ) be a bounded unital homomorphism, and let α : A → A \alpha:\mathcal A\to\mathcal A α : A → A b…
Does there exist an absolute constant C > 0 C>0 C > 0 such that every Dirichlet polynomial f ( s ) = ∑ n = 1 N a n n − s f(s)=\sum_{n=1}^{N}a_n n^{-s} f ( s ) = ∑ n = 1 N a n n − s satisfies …
Given two square nonnegative integer matrices A ∈ N m × m A\in\mathbb{N}^{m\times m} A ∈ N m × m and B ∈ N n × n B\in\mathbb{N}^{n\times n} B ∈ N n × n , determine whether they are strong shift equivalent: that is, whether th…
Let Ω ⊂ Q p d \Omega\subset\mathbb{Q}_p^d Ω ⊂ Q p d be an admissible bounded domain, let D Ω α D_{\Omega}^{\alpha} D Ω α denote the Dirichlet realization of the Vladimirov–Taibleson operator, and let…
For each 1 ≤ p < ∞ 1\le p<\infty 1 ≤ p < ∞ and α > − 1 \alpha>-1 α > − 1 , determine exactly which analytic symbols g g g make the Volterra-type operators J g J_g J g and I g I_g I g metrically bounded on the area Nevanlinna sp…
Let H 2 ( D ) H^2(\mathbb D) H 2 ( D ) be the Hardy space of the unit disk. Define the Cesàro operator C : H 2 ( D ) → H 2 ( D ) C:H^2(\mathbb D)\to H^2(\mathbb D) C : H 2 ( D ) → H 2 ( D ) by…
Let D = { z ∈ C : ∣ z ∣ < 1 } \mathbb{D}=\{z\in\mathbb{C}:|z|<1\} D = { z ∈ C : ∣ z ∣ < 1 } , let A ( D ) A(\mathbb{D}) A ( D ) denote the disk algebra, and let A 2 ( D ) A^2(\mathbb{D}) A 2 ( D ) be the Bergman space. For h ∈ A ( D ) h\in A(\mathbb{D}) h ∈ A ( D ) , define the Bergman…
For every n ∈ N n\in\mathbb{N} n ∈ N and every Hermitian matrix-valued Laurent polynomial P ( z , w ) = ∑ ( j , k ) ∈ F A j , k z j w k ∈ M n ( C [ z ± 1 , w ± 1 ] ) P(z,w)=\sum_{(j,k)\in F}A_{j,k}z^jw^k\in M_n\!\left(\mathbb{C}[z^{\pm1},w^{\pm1}]\right) P ( z , w ) = ∑ ( j , k ) ∈ F A j , k z j w k ∈ M n ( C [ z ± 1 , w ± 1 ] ) satisfyin…
For every n , m ≥ 1 n,m\ge 1 n , m ≥ 1 , every matrix A ∈ M n ( C ) A\in M_n(\mathbb{C}) A ∈ M n ( C ) , and every matrix-valued polynomial P ( z ) = ∑ k = 0 d P k z k P(z)=\sum_{k=0}^d P_k z^k P ( z ) = ∑ k = 0 d P k z k with P k ∈ M m ( C ) P_k\in M_m(\mathbb{C}) P k ∈ M m ( C ) , one has…
For every integer n ≥ 3 n\ge 3 n ≥ 3 , every n n n -manifold N N N , and every parameter γ \gamma γ with 0 ≤ γ < 2 n n − 1 0\le \gamma<\frac{2n}{n-1} 0 ≤ γ < n − 1 2 n , the connected sum T n # N \mathbb{T}^n\# N T n # N admits no complete Riemanni…
Let H \mathcal{H} H be a complex Hilbert space and let U , V ∈ B ( H ) U,V\in\mathcal{B}(\mathcal{H}) U , V ∈ B ( H ) be invertible. If ( U − 1 ) ( V − 1 ) (U-\mathbf{1})(V-\mathbf{1}) ( U − 1 ) ( V − 1 ) and ( V − 1 ) ( U − 1 ) (V-\mathbf{1})(U-\mathbf{1}) ( V − 1 ) ( U − 1 ) belong to…
Does there exist an infinite-dimensional Banach space X X X such that every bounded linear operator T ∈ L ( X , X ) T\in\mathcal{L}(X,X) T ∈ L ( X , X ) attains its norm; that is, for every T ∈ L ( X , X ) T\in\mathcal{L}(X,X) T ∈ L ( X , X ) …
For every integer n ≥ 1 n\ge 1 n ≥ 1 , every matrix A ∈ C n × n A\in\mathbb{C}^{n\times n} A ∈ C n × n , and every polynomial p ∈ C [ z ] p\in\mathbb{C}[z] p ∈ C [ z ] , one has ∥ p ( A ) ∥ 2 ≤ 2 sup z ∈ W ( A ) ∣ p ( z ) ∣ \|p(A)\|_2\le 2\sup_{z\in W(A)}|p(z)| ∥ p ( A ) ∥ 2 ≤ 2 sup z ∈ W ( A ) ∣ p ( z ) ∣ , where…
For Hermitian matrices A 1 , A 2 ∈ M n ( C ) A_{1},A_{2}\in M_{n}(\mathbb{C}) A 1 , A 2 ∈ M n ( C ) , define p ( z 0 , z 1 , z 2 ) = det ( z 0 I + z 1 A 1 + z 2 A 2 ) p(z_{0},z_{1},z_{2})=\det\!\left(z_{0}I+z_{1}A_{1}+z_{2}A_{2}\right) p ( z 0 , z 1 , z 2 ) = det ( z 0 I + z 1 A 1 + z 2 A 2 ) . Kippenhahn's conjecture asserts that if th…
For each n ≥ 1 n\geq 1 n ≥ 1 , define S n S_n S n to be the least constant such that, for every n n n -dimensional complex Banach space X X X and every invertible operator T ∈ L ( X ) T\in\mathcal{L}(X) T ∈ L ( X ) ,…
For every finitely generated polynomial submodule M ⊂ H 2 ( D 2 ) M\subset H^2(\mathbb D^2) M ⊂ H 2 ( D 2 ) , Yang's numerical invariants satisfy Σ 0 ( M ) ≥ Σ 1 ( M ) ≥ Σ 2 ( M ) ≥ ⋯ \Sigma_0(M)\geq \Sigma_1(M)\geq \Sigma_2(M)\geq\cdots Σ 0 ( M ) ≥ Σ 1 ( M ) ≥ Σ 2 ( M ) ≥ ⋯ .
Direct-summand conjecture. If