On the Neumann-Poincaré operator

Josef Král; Dagmar Medková

Displaying similar documents to “On the Neumann-Poincaré operator”

A differential equation related to the $l^{p}$ -norms

Jacek Bojarski, Tomasz Małolepszy, Janusz Matkowski (2011)

Annales Polonici Mathematici

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Let p ∈ (1,∞). The question of existence of a curve in ℝ₊² starting at (0,0) and such that at every point (x,y) of this curve, the $l^{p}$ -distance of the points (x,y) and (0,0) is equal to the Euclidean length of the arc of this curve between these points is considered. This problem reduces to a nonlinear differential equation. The existence and uniqueness of solutions is proved and nonelementary explicit solutions are given.

Essential norms of the Neumann operator of the arithmetical mean

Josef Král, Dagmar Medková (2001)

Mathematica Bohemica

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Let $K \subset ℝ^{m}$ ( $m \geq 2$ ) be a compact set; assume that each ball centered on the boundary $B$ of $K$ meets $K$ in a set of positive Lebesgue measure. Let $C_{0}^{(1)}$ be the class of all continuously differentiable real-valued functions with compact support in $ℝ^{m}$ and denote by $σ_{m}$ the area of the unit sphere in $ℝ^{m}$ . With each $ϕ \in C_{0}^{(1)}$ we associate the function $W_{K} ϕ (z) = \frac{1}{σ_{m}} \underset{ℝ^{m} ∖ K}{\to} \int g r a d ϕ (x) \cdot \frac{z - x}{{| z - x |}^{m}} x$ of the variable $z \in K$ (which is continuous in $K$ and harmonic in $K ∖ B$ ). $W_{K} ϕ$ depends only on the restriction ${ϕ |}_{B}$ of $ϕ$ to the boundary $B$ of $K$ . This gives rise to a linear operator $W_{K}$ ...

On ramified covers of the projective plane II: Generalizing Segre’s theory

Michael Friedman, Rebecca Lehman, Maxim Leyenson, Mina Teicher (2012)

Journal of the European Mathematical Society

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The classical Segre theory gives a necessary and sufficient condition for a plane curve to be a branch curve of a (generic) projection of a smooth surface in $ℙ^{3}$ . We generalize this result for smooth surfaces in a projective space of any dimension in the following way: given two plane curves, $B$ and $E$ , we give a necessary and sufficient condition for $B$ to be the branch curve of a surface $X$ in $ℙ^{N}$ and $E$ to be the image of the double curve of a $ℙ^{3}$ -model of $X$ . In the classical Segre theory, a...

Subharmonicity in von Neumann algebras

Thomas Ransford, Michel Valley (2005)

Studia Mathematica

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Let ℳ be a von Neumann algebra with unit $1_{ℳ}$ . Let τ be a faithful, normal, semifinite trace on ℳ. Given x ∈ ℳ, denote by $μ_{t} {(x)}_{t \geq 0}$ the generalized s-numbers of x, defined by $μ_{t} (x)$ = inf||xe||: e is a projection in ℳ i with $τ (1_{ℳ} - e)$ ≤ t (t ≥ 0). We prove that, if D is a complex domain and f:D → ℳ is a holomorphic function, then, for each t ≥ 0, $λ \mapsto \int_{0}^{t} l o g μ_{s} (f (λ)) d s$ is a subharmonic function on D. This generalizes earlier subharmonicity results of White and Aupetit on the singular values of matrices.

On the UMD constant of the space $ℓ ₁^{N}$

Adam Osękowski (2016)

Colloquium Mathematicae

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Let N ≥ 2 be a given integer. Suppose that $d f = {(d f ₙ)}_{n \geq 0}$ is a martingale difference sequence with values in $ℓ ₁^{N}$ and let ${(ε ₙ)}_{n \geq 0}$ be a deterministic sequence of signs. The paper contains the proof of the estimate $ℙ (s u p_{n \geq 0} | | \sum_{k = 0}^{n} ε_{k} d f_{k} {| |}_{ℓ ₁^{N}} \geq 1) \leq (l n N + l n (3 l n N)) / (1 - {(2 l n N)}^{- 1}) s u p_{n \geq 0} | | \sum_{k = 0}^{n} d f_{k} {| |}_{ℓ ₁^{N}}$ . It is shown that this result is asymptotically sharp in the sense that the least constant $C_{N}$ in the above estimate satisfies $l i m_{N \to \infty} C_{N} / l n N = 1$ . The novelty in the proof is the explicit verification of the ζ-convexity of the space $ℓ ₁^{N}$ .

Recovering an algebraic curve using its projections from different points. Applications to static and dynamic computational vision

Jeremy Yirmeyahu Kaminski, Michael Fryers, Mina Teicher (2005)

Journal of the European Mathematical Society

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We study some geometric configurations related to projections of an irreducible algebraic curve embedded in $ℂ ℙ^{3}$ onto embedded projective planes. These configurations are motivated by applications to static and dynamic computational vision. More precisely, we study how an irreducible closed algebraic curve $X$ embedded in $ℂ ℙ^{3}$ , of degree $d$ and genus $g$ , can be recovered using its projections from points onto embedded projective planes. The embeddings are unknown. The only input is the defining...

On a modification of the Poisson integral operator

Dariusz Partyka (2011)

Annales Universitatis Mariae Curie-Sklodowska, sectio A – Mathematica

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Given a quasisymmetric automorphism $γ$ of the unit circle $𝕋$ we define and study a modification $P_{γ}$ of the classical Poisson integral operator in the case of the unit disk $𝔻$ . The modification is done by means of the generalized Fourier coefficients of $γ$ . For a Lebesgue’s integrable complexvalued function $f$ on $𝕋$ , $P_{γ} [f]$ is a complex-valued harmonic function in $𝔻$ and it coincides with the classical Poisson integral of $f$ provided $γ$ is the identity mapping on $𝕋$ . Our considerations are motivated by...

An arithmetic Riemann-Roch theorem for pointed stable curves

Gérard Freixas Montplet (2009)

Annales scientifiques de l'École Normale Supérieure

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Let $(𝒪, Σ, F_{\infty})$ be an arithmetic ring of Krull dimension at most 1, $𝒮 = Spec 𝒪$ and $(π : 𝒳 \to 𝒮; σ_{1}, ..., σ_{n})$ an $n$ -pointed stable curve of genus $g$ . Write $𝒰 = 𝒳 ∖ \cup_{j} σ_{j} (𝒮)$ . The invertible sheaf $ω_{𝒳 / 𝒮} (σ_{1} + \dots + σ_{n})$ inherits a hermitian structure ${∥ \cdot ∥}_{hyp}$ from the dual of the hyperbolic metric on the Riemann surface $𝒰_{\infty}$ . In this article we prove an arithmetic Riemann-Roch type theorem that computes the arithmetic self-intersection of $ω_{𝒳 / 𝒮} {(σ_{1} + ... + σ_{n})}_{hyp}$ . The theorem is applied to modular curves $X (Γ)$ , $Γ = Γ_{0} (p)$ or $Γ_{1} (p)$ , $p \geq 11$ prime, with sections given by the cusps. We show $Z^{'} (Y (Γ), 1) \sim e^{a} π^{b} Γ_{2} {(1 / 2)}^{c} L (0, ℳ_{Γ})$ , with $p \equiv 11 m o d 12$ when $Γ = Γ_{0} (p)$ . Here $Z (Y (Γ), s)$ is the Selberg...

On a theorem of Lindelof

Vladimir Ya. Gutlyanskii, Olli Martio, Vladimir Ryazanov (2011)

Annales Universitatis Mariae Curie-Sklodowska, sectio A – Mathematica

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We give a quasiconformal version of the proof for the classical Lindelof theorem: Let $f$ map the unit disk $𝔻$ conformally onto the inner domain of a Jordan curve $𝒞$ : Then $𝒞$ is smooth if and only if arg $f^{'} (z)$ has a continuous extension to $\bar{𝔻}$ . Our proof does not use the Poisson integral representation of harmonic functions in the unit disk.

An iterative construction for ordinary and very special hyperelliptic curves

Francis J. Sullivan (1983)

Atti della Accademia Nazionale dei Lincei. Classe di Scienze Fisiche, Matematiche e Naturali. Rendiconti Lincei. Matematica e Applicazioni

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Si costruiscono famiglie di curve iperellittiche col $p$ —rango della varietà jacobiana uguale a zero. La costruzione sfrutta le proprietà elementari dell’operatore di Cartier e delle estensioni $p$ -cicliche dei corpi con la caratteristica $p$ maggiore di zero.

Syzygies and logarithmic vector fields along plane curves

Alexandru Dimca, Edoardo Sernesi (2014)

Journal de l’École polytechnique — Mathématiques

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We investigate the relations between the syzygies of the Jacobian ideal of the defining equation for a plane curve $C$ and the stability of the sheaf of logarithmic vector fields along $C$ , the freeness of the divisor $C$ and the Torelli properties of $C$ (in the sense of Dolgachev-Kapranov). We show in particular that curves with a small number of nodes and cusps are Torelli in this sense.

Elliptic curves with $ℚ (ℰ [3]) = ℚ (ζ_{3})$ and counterexamples to local-global divisibility by 9

Laura Paladino (2010)

Journal de Théorie des Nombres de Bordeaux

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We give a family $ℱ_{h, β}$ of elliptic curves, depending on two nonzero rational parameters $β$ and $h$ , such that the following statement holds: let $ℰ$ be an elliptic curve and let $ℰ [3]$ be its 3-torsion subgroup. This group verifies $ℚ (ℰ [3]) = ℚ (ζ_{3})$ if and only if $ℰ$ belongs to $ℱ_{h, β}$ . Furthermore, we consider the problem of the local-global divisibility by 9 for points of elliptic curves. The number 9 is one of the few exceptional powers of primes, for which an answer...

Structure of the McMullen domain in the parameter planes for rational maps

Robert L. Devaney (2005)

Fundamenta Mathematicae

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We show that, for the family of functions $F_{λ} (z) = z ⁿ + λ / z ⁿ$ where n ≥ 3 and λ ∈ ℂ, there is a unique McMullen domain in parameter space. A McMullen domain is a region where the Julia set of $F_{λ}$ is homeomorphic to a Cantor set of circles. We also prove that this McMullen domain is a simply connected region in the plane that is bounded by a simple closed curve.