Sökning: "Fourier coefficients"

Visar resultat 11 - 15 av 30 avhandlingar innehållade orden Fourier coefficients.

1. 11. Automorphic string amplitudes

   Författare :Henrik Gustafsson; Chalmers tekniska högskola; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; Eisenstein series; string theory; automorphic forms; U-duality; non-perturbative effects; Whittaker vectors; instantons;

   Sammanfattning : This thesis explores the non-perturbative properties of higher derivative interactions appearing in the low-energy expansion of four-graviton scattering amplitudes in toroidal compactifications of type IIB string theory. We summarise the arguments for finding such higher derivative corrections in terms of automorphic forms using U-duality, supersymmetry and string perturbation theory. LÄS MER

3. 12. Automorphic forms and string theory: Small automorphic representations and non-perturbative effects

   Författare :Henrik Gustafsson; Chalmers tekniska högskola; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; instantons; automorphic forms; automorphic representations; Eisenstein series; U-duality; non-perturbative effects; string theory;

   Sammanfattning : This compilation thesis stems from a project with the purpose of determining non-perturbative contributions to scattering amplitudes in string theory carrying important information about instantons, black hole quantum states and M-theory. The scattering amplitudes are functions on the moduli space invariant under the discrete U-duality group and this invariance is one of the defining properties of an automorphic form. LÄS MER

4. 13. Computations of Automorphic Functions on Fuchsian Groups

   Författare :Helen Avelin; Andreas Strömbergsson; Dennis Hejhal; Warwick Tucker; Michael Rubinstein; Uppsala universitet; []
   Nyckelord :Mathematics; 11F72; 11F03; 11F06; 11Y35; 11-04; 11Y16; 33F06; 34B27; 33F05; MATEMATIK;

   Sammanfattning : This thesis consists of four papers which all deal with computations of automorphic functions on cofinite Fuchsian groups. In the first paper we develop an algorithm for numerical computation of the Eisenstein series. We focus in particular on the computation of the poles of the Eisenstein series. LÄS MER

5. 14. NMR diffusion studies on lyotropic liquid crystalline systems

   Författare :Greger Orädd; Frank Volke; Umeå universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Diffusion; pulsed field gradient; liquid crystalline systems; lipid lateral diffusion; cubic phases; peptide-lipid interactions; hydrophobic mismatch; permeability;

   Sammanfattning : The pulsed field gradient fourier transform nuclear magnetic resonance (PFG-FTNMR) method to measure translational diffusion coefficients in multicomponent systems has been applied to amphiphilic molecules forming liquid crystalline phases.By analyzing the concentration dependence of the diffusion coefficients of water and amphiphile in a micellar system of N,N-dimethyldodecy lamine oxide (DDAO) in water it was possible to conclude that the micelles formed were polydisperse in size and shape. LÄS MER

7. 15. Uncertainty Quantification and Numerical Methods for Conservation Laws

   Författare :Per Pettersson; Jan Nordström; Gianluca Iaccarino; Gunilla Kreiss; Rémi Abgrall; Uppsala universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; uncertainty quantification; polynomial chaos; stochastic Galerkin methods; conservation laws; hyperbolic problems; finite difference methods; finite volume methods; Beräkningsvetenskap med inriktning mot numerisk analys; Scientific Computing with specialization in Numerical Analysis;

   Sammanfattning : Conservation laws with uncertain initial and boundary conditions are approximated using a generalized polynomial chaos expansion approach where the solution is represented as a generalized Fourier series of stochastic basis functions, e.g. orthogonal polynomials or wavelets. LÄS MER