Sökning: "Joachim Toft"

Visar resultat 1 - 5 av 8 avhandlingar innehållade orden Joachim Toft.

  1. 1. Continuity and Positivity Problems in Pseudo-differential Calculus

    Författare :Joachim Toft; Matematik (naturvetenskapliga fakulteten); []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; funktionsanalys; fourieranalys; Serier; functional analysis; Fourier analysis; Series; Entropy.; Young s inequality; Twisted convolution; Schatten-von Neumann; Lower bounds; Weyl Calculus; Pseudo-differential Operqator; Continuity; Positivity;

    Sammanfattning : The paper deals with various positivity and continuity questions arising in the Weyl calculus of pseudo-differential operators. Let W be a symplectic vector space. LÄS MER

  3. 2. Numerical Conformal mappings for regions Bounded by Smooth Curves

    Författare :Anders Andersson; Börje Nilsson; Joachim Toft; Michael Benedicks; Växjö universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Schwarz-Christoffel mapping; rounded corners; tangent polygons; outer polygon; zipper algorithm; Schwarz-Christoffelavbildningen; rundade hörn; tangentpolygoner; yttre polygoner; zipper-algoritmer; Applied mathematics; Tillämpad matematik; Mathematics; Matematik;

    Sammanfattning : Inom många tillämpningar används konforma avbildningar för att transformera tvådimensionella områden till områden med enklare utseende. Ett exempel på ett sådant område är en kanal av varierande tjocklek begränsad av en kontinuerligt deriverbar kurva. LÄS MER

  4. 3. Numerical Conformal Mappings for Waveguides

    Författare :Anders Andersson; Börje Nilsson; Joachim Toft; Michael Benedicks; Växjö universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; waveguide; building block method; numerical conformal mappings; Schwarz–Christoffel mapping; rounded corners method; approximate curve factors; outer polygon method; boundary curvature; zipper method; geodesic algorithm; acoustic wave scattering; electro-magnetic wave scattering; Applied mathematics; Tillämpad matematik; Mathematics; Matematik;

    Sammanfattning : Acoustic or electro-magnetic scattering in a waveguide with varying direction and cross-section can be re-formulated as a two-dimensional scattering problem, provided that the variations take place in only one dimension at a time. By using the so-called Building Block Method, it is possible to construct the scattering properties of a combination of scatterers when the properties of each scatterer are known. LÄS MER

  5. 4. Continuity and compositions of operators with kernels in ultra-test function and ultra-distribution spaces

    Författare :Yuanyuan Chen; Joachim Toft; Nenad Teofanov; Linnéuniversitetet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Composition; modulation spaces; positivity; pseudo-differential operators; Schatten-von Neumann operators; twisted convolutions; ultra-distributions; Matematik; Mathematics;

    Sammanfattning : In this thesis we consider continuity and positivity properties of pseudo-differential operators in Gelfand-Shilov and Pilipović spaces, and their distribution spaces. We also investigate composition property of pseudo-differential operators with symbols in quasi-Banach modulation spaces. LÄS MER

  7. 5. Propagation of singularities for pseudo-differential operators and generalized Schrödinger propagators

    Författare :Karoline Johansson; Joachim Toft; Anders Olofsson; Linnéuniversitetet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Banach spaces; Fourier; Generalized time-dependent Schrödinger equation; Micro-local; Modulation spaces; Non-tangential convergence; Pseudo-differential operators; Regularity; Wave-front sets; Banachrum; Fourier; Generaliserad tidsberoende Schrödinger ekvation; Icke-tangentiell konvergens; Mikrolokal; Modulationsrum; Pseudodifferentialoperatorer; Regularitet; Vågfrontsmängder; Mathematical analysis; Analys; Mathematics; Matematik;

    Sammanfattning : In this thesis we discuss different types of regularity for distributions which appear in the theory of pseudo-differential operators and partial differential equations. Partial differential equations often appear in science and technology. LÄS MER