Klaus Kirsten

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Spectral functions relevant in the context of quantum field theory under the influence of spherically symmetric external conditions are analysed. Examples comprise heatkernels, determinants and spectral sums needed for the analysis of Casimir energies. First, we summarize that a convenient way of handling them is to use the associated zeta function. A way(More)
We develop a formalism for the calculation of the ground state energy of a spinor field in the background of a cylindrically symmetric magnetic field. The energy is expressed in terms of the Jost function of the associated scattering problem. Uniform asymptotic expansions needed are obtained from the Lippmann-Schwinger equation. The general results derived(More)
We consider zeta functions and heat-kernel expansions on the bounded, generalized cone in arbitrary dimensions using an improved calculational technique. The specific case of a global monopole is analysed in detail and some restrictions thereby placed on the A5/2 coefficient. The computation of functional determinants is also addressed. General formulas are(More)
Local boundary conditions for spinor fields are expressed in terms of a 1parameter family of boundary operators, and find applications ranging from (supersymmetric) quantum cosmology to the bag model in quantum chromodynamics. The present paper proves that, for massless spinor fields on the Euclidean ball in dimensions d = 2, 4, 6, the resulting ζ(0) value(More)
We calculate the heat-kernel coefficients, up to a 2 , for a U(1) bundle on the 4-Ball for boundary conditions which are such that the normal derivative of the field at the boundary is related to a first-order operator in boundary derivatives acting on the field. The results are used to place restrictions on the general forms of the coefficients. In the(More)
Motivated by the need to give answers to some fundamental questions in quantum field theory, during the last years there has been and continues to be a lot of interest in the problem of calculating the heat-kernel coefficients and the determinant of a differential operator, L (see for example [1, 2, 3]). In mathematics the interest in the heat-kernel(More)